Main headlights went out...brights and fogs still work [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Main headlights went out...brights and fogs still work


Surveyor313
03-20-2009, 10:02 PM
Hey fellow trailvoys,

Earlier this afternoon, I headed out and when the sun went down, I noticed my headlights weren't working. I checked my brights and fogs and they work fine.

Any ideas what could've happened? Could a fuse be the cause?

They were both working earlier today (I noticed them coming on when I used the remote to unlock the doors). Kind of strange for them to both go out at the same time...:confused:

Thanks :thumbsup:

MajesticLT03
03-20-2009, 10:36 PM
check fuses and if they are fine check voltage to the headlamp switch

the roadie
03-21-2009, 02:20 AM
The left and right don't share a single fuse. There is one for each side (#3 and #6). The first place that left and right lows come together is the underhood relay 46.

I could post a schematic if you have a meter and want to trace signals. Or give you some hints. But the relay may be it. Swap with the adjacent one of the same kind that runs the fan clutch. You can be without the fan for a few minutes.

Surveyor313
03-21-2009, 09:53 AM
Thanks.

I'm gonna go check out those right now...

I'll come back and post what the problem was.

Surveyor313
03-21-2009, 10:30 AM
Well,

Both the fuses are good. So when I switched the relays, the passenger headlight is on and the driver turn signal light is on. Both turn signals work when you try them.

Might be time for some new relays...I'll be back when I know more.

the roadie
03-21-2009, 12:26 PM
A bad relay alone couldn't cause those symptoms, since the low beam relay is shared by both sides. If your low beam driver's side lamp blew with a massive short, the fuse should have blown quickly to protect the solid state relay, but perhaps it didn't, and the relay is now damaged.

You may need one new relay and one low beam lamp. I usually buy two at once because if one blows for being old, the other one is usually close behind.

I haven't figured out a way that the headlight relay could interact at all with the turn/marker lamp circuits, unless there's a wiring harness short. Let's fix the headlights first, because those are a safety issue.

Surveyor313
03-21-2009, 12:34 PM
Just got back from my quest to find relays...I checked Advance, NAPA, Pep Boys...none of them have relays. NAPA is the only one who can even order them...for $49.99 apiece. Haven't ordered any yet...

I figured it would be a good idea to order 2 if I did have to order. Advance suggested me go to a junkyard...I'm not so sure because I could be getting a couple that are gonna go bad like mine??

I'm trying to avoid going to the dealer...figured it would be an arm and a leg to get some there.

If I need a new headlight, I have to replace the whole lamp, not just one bulb, correct?

Looks like I won't be driving around at night for a few days anyway...not sure the FL laws about driving with fogs only...:undecided

the roadie
03-21-2009, 12:51 PM
Low and high beams are separate bulbs.

Solid state relays are a very rare failure item. I don't carry a spare, and I'm usually a nut case about carrying extras of things I think will fail.

That relay (15016745) is dealer list price of about $45. gmpartsdirect.com has it for $25. Make sure you try cross-referencing it with Airtex 1R1944. Rockauto.com (one of my favorite vendors) has that for $28.

Preston
03-21-2009, 12:57 PM
This is off of napafix that we use at work...may or may not help...good luck


Vehicle Application: 2003 Chevrolet Trailblazer 4.2L 2004 GMC Envoy XL 4.2L, Vin S, Eng Cfg L6

Customer Concern: There are no low beams or Daytime Running Light (DRL) operation. The high beams and flash to pass work fine.
Tests/Procedures: 1. In the underhood fuse box verify the HDM fuse to verify it is hot at all times.

2. If OK, then swap the HDM relay #46 with another similar relay and see if the lights start working.

3. If the lights do not work, check the Pink/White wire from the relay to the Body Control Module (BCM) for opens or shorts to ground.

4. If the wire is OK probe the wire to see if there is a square wave signal on the wire with lights commanded on.
Potential Causes: Open Fuse
HDM Relay
Wiring

Surveyor313
03-22-2009, 03:39 PM
Thanks for the help, guys.

I went ahead and ordered 2 relays (from gmpartsdirect.com---thanks roadie) I know one's bad for sure, b/c when I switched them, some of the lights did work.

After I put in the new relays, if some of the lights still don't work, I'll try getting new bulbs for them.

Hopefully that's all and not a wiring problem. After the relays come in, I'll post the results.

Thanks again.

Surveyor313
04-07-2009, 07:35 PM
Hey guys,

Well I had a little problem with FedEx delivering my relays to me (long story :x), but the good news is I finally got my relays over the weekend, and sure enough, it fixed the problem. Everything seems to be working fine now. :thumbsup:

Now, just for the hell of it, I wonder how this happened in the first place? If these relays are rare failures, I wonder what might have caused this....I do know that the day that my lights went out, I went through one of those drive-through car washes and I got the max treatment which does everything including the underbody. I wonder if some water got up in there and shorted something out?

Any thoughts?


Thanks guys, I've learned so much cool info from y'all over the past year that I've been a member.
:thx :thx :thx

the roadie
04-07-2009, 07:52 PM
Knowing a bit about how they're designed, there's nothing short of a REALLY strong static spark that should be able to take them out. Certainly nothing a car wash would normally give out, since humidity and soap films tend to dissipate static build-up. Root cause is going to be unknowable.

Surveyor313
04-07-2009, 08:43 PM
10-4 Roadie. Thanks for the help, and now maybe if someone else has a similar problem, this thread can help them out.

:tiphat

2003TrailLBZ
06-08-2009, 10:43 AM
I have a similar issue with my headlights on my 03Trailblazer. The headlights turn on and off at random, but the driving lights and high beams work. You can be driving down the road and "off the lights go". But the driving lights stay on, a few minutes later the low beams come back on. Any thoughts? Tks Craig

rbarrios
06-08-2009, 01:26 PM
This relay- I think is solid state--- and not mechanical...
But- when something like this happens--- it may be heat or cold related...
in your case-- it may be heating up and causing a failure--- cools down- and works again...
But next time it happens- get out and jiggle that relay around--- or remove and put back in... no go?... replace with the fan clutch relay...

2003TrailLBZ
06-08-2009, 02:42 PM
This relay- I think is solid state--- and not mechanical...
But- when something like this happens--- it may be heat or cold related...
in your case-- it may be heating up and causing a failure--- cools down- and works again...
But next time it happens- get out and jiggle that relay around--- or remove and put back in... no go?... replace with the fan clutch relay...

I will try, the lights usually go off when we are go down the road and unable to pull over. You think it could be the headlight swith?? Or I guess maybe the high/low lever on the column itself? Craig

Loverotties
06-08-2009, 04:21 PM
I have a similar issue with my headlights on my 03Trailblazer. The headlights turn on and off at random, but the driving lights and high beams work. You can be driving down the road and "off the lights go". But the driving lights stay on, a few minutes later the low beams come back on. Any thoughts? Tks Craig

I have had the same thing happend to me!It hasn't done in a while,but of corse you know it will start happening again!

CoyoteFireGuy
06-08-2009, 11:03 PM
Next time it happens take a blunt object and hit the side of the dash where the cubby hole is on the drivers side, with the door open. Fixes it everytime on mine.(I use a mag lite) I have chaulked it up to ghost wiring in the switch housing.FYI sometimes you have to hit it pretty hard, not hard enough to damage the dash, but HARD.:m2:

2003TrailLBZ
06-08-2009, 11:30 PM
Next time it happens take a blunt object and hit the side of the dash where the cubby hole is on the drivers side, with the door open. Fixes it everytime on mine.(I use a mag lite) I have chaulked it up to ghost wiring in the switch housing.FYI sometimes you have to hit it pretty hard, not hard enough to damage the dash, but HARD.:m2:

I will give that a try. Hey, if you cant fix it with a hammer, it must be a electrical problem!!!!!!! Its just very frustrating problem. Rgds Craig

CoyoteFireGuy
06-09-2009, 12:05 AM
I will give that a try. Hey, if you cant fix it with a hammer, it must be a electrical problem!!!!!!! Its just very frustrating problem. Rgds Craig

Try while drving on dark roads and not having fog lights :mad::hissy::bonk:

85vette
06-12-2009, 09:47 PM
It's my turn now! My wife left something from work in the company vehicle and I drove her up there in the TB...just before we get there the headlights went out!?! They wouldn't turn on manually either. We left the TB at her work and had to drive the company car home. I figured I'd find something about this on the forum. I'll see if they work tommorrow, maybe they will cool off and work again? $49.00 relays, huh? We have a zero deductible Platinum Extended Warranty on it, I think I'll let them take care of this. I'm starting to think there is an electrical gremlin at work here...just a few weeks ago the anti-lock brake light came on one night and wouldn't go out...until the next day:undecided

85vette
06-13-2009, 10:10 AM
I called the dealer (50 miles away) and he said to bring it in....Cranked up the TB, now the headlights work again after it sat overnight....gremlins....:undecided

Robert1101
06-13-2009, 11:29 AM
Relays get corroded lugs and other things. Pull the relay and tap on it a few times, not hard enough to break the plastic housing. Plug and unplug it 8-10 times to clean up the lugs and see if that takes care of it. 75% or so of most problems are dirty connectors and dirty lugs.

the roadie
06-13-2009, 12:50 PM
Were your lows dead, or both hi and low beams? Different relays involved.

04_Tblazer_LT
06-13-2009, 02:04 PM
I had the same thing happen twice now, most recent was last night. After I let it sit for 45 minutes to an hour all was well again. I was wondering about this though last winter I replaced the oem low beam bulbs with sylvania xtravsion bulbs when one side burned out. Could these be drawing too much and causing the relay to get hot?

85vette
06-13-2009, 02:45 PM
Were your lows dead, or both hi and low beams? Different relays involved.

Frankly, I never checked to see it the high beams would work. It was 830, and we had to drive 16 miles, so we just parked it and left. I tried the manual switch, and even locked and unlocked it with the fob a few times, but only spent about 2 minutes at most. If it happens again I'll be sure to see if the high beams work, as well as the driving/fog lights. The service manager at the dealer said something had to have happened to cause the PCM to shut down the lights, but advised me to see if the problem duplicated itself. As you know, electrical problems are often of such nature that if it's not happening at the time the technician is looking at it they just NPF (no problem found) it on the service order. But I understand, I know those warranty companies aren't going to pay them to spend a lot of time on the problem or let them guess which parts are faulty on their dime. That's why we purchased a good extended warranty to begin with, I knew with all the electronics on this truck something expensive was bound to fail. Never thought it would be the headlights though?!:eek:

the roadie
06-13-2009, 05:18 PM
I had the same thing happen twice now, most recent was last night. After I let it sit for 45 minutes to an hour all was well again. I was wondering about this though last winter I replaced the oem low beam bulbs with sylvania xtravsion bulbs when one side burned out. Could these be drawing too much and causing the relay to get hot?Same question - was it the lows only that quit on you? There are two relays involved. The high beams use a traditional relay with contacts that could conceivably get hot, but it could also be the relay socket contacts. IF YOU HAVE A HIGH BEAM FAILURE: Best thing is to exchange that relay with an identical one next door if it happens again. Front relay 43 is the HI beams. Swap it with the identical one next door - 42, which is the windshield washer pump. IF YOU HAVE A LOW BEAM FAILURE: Swap relay 46 for the identical one - 45, next to it, which runs the cooling fan clutch.

http://www.roadie.org/frontfuses.jpg

The low beam relays are different, and more expensive, because they aren't the traditional kind with physical contacts inside, like this:

http://upload.wikimedia.org/wikipedia/commons/2/24/Relay.jpg

They are solid state (semiconductor) items, so they can be turned on and off at a much higher speed than normal relays. The fan clutch needs one of those to continuously vary its speed under PCM control, and the low beams need one to operate the DRL function. The daytime running light function actually turns the low beams on about 70% of the time and off 30% of the time, at hundreds of times per second. This is done with a PWM waveform (pulse width modulated) which you can Google for if you want more reading. It's the fast ON/OFF switching of the low beam relay that absolutely KILLS some lamps and all HID ballasts if you change from the OEM bulbs.

Frankly, I never checked to see it the high beams would work. If it failed while you're driving in the dark I heartily recommend trying anything in reach. When I was in pilot training, at night, my instructor reached over and turned off the instrument lights and asked what I'd do. I calmly reached into my shirt pocket and pulled out a mini-maglight and held it in my mouth while I continued to fly the plane. He snatched it away and said, what next, wise guy. I pulled out mini-maglight #2 from a sleeve pocket. He snatched that. I pulled out my BIG maglight from my flight bag. He snatched that. I finally had to manage the plane's engine RPM and airspeed by reference to the engine and wind noise, not seeing any of the instruments. THAT was the lesson he wanted to teach me, not discover how many spare flashlights I was carrying within reach. :duh:

04_Tblazer_LT
06-15-2009, 10:37 AM
yes just the low beams went out, everything else worked. Ended up driving with the high beams or fogs (depending on oncoming traffic) most of the way back home. Thanks for the information.

wab9rock
07-15-2009, 08:10 PM
The left and right don't share a single fuse. There is one for each side (#3 and #6). The first place that left and right lows come together is the underhood relay 46.

I could post a schematic if you have a meter and want to trace signals. Or give you some hints. But the relay may be it. Swap with the adjacent one of the same kind that runs the fan clutch. You can be without the fan for a few minutes.

My dim lights had quit working so I went out and swapped the relays and wouldn't you know my dim lights now work. Thanks alot for the suggestions on dim lights not working.

tfrench91223
07-16-2009, 12:08 AM
I have an 03 Trailblazer with the same issues.. Is there anyway to actually check and see if the relay is bad.??. My headlights turn off randomly.. Sometimes not long enough to swith the relays out to test them.

Loverotties
07-16-2009, 12:24 AM
Same here tfrench!

the roadie
07-16-2009, 01:49 PM
It's a solid state relay, which makes it more difficult to test, but also less likely to fail than the socket it plugs into. Just swap with its identical neighbor and see if the symptoms change. If you start to overheat at stop lights, the relay is definitely bad. (when you swap the lo beam relay for the fan clutch relay)

tfrench91223
07-17-2009, 05:56 PM
So what are the chances that the fan clutch relay and the low beam relay are failing at the same time.. I've been having the issues with the my low beams turning off randomly.. Now it seems as if my clutch is not kicking in.. When i turn on my a/c the fan does not spin any faster.. while driving down the road with the a/c on my trailblazer will start to run hot.. If i turn off the a/c it goes back to a normal temp... Autozone can order the relay for 38.99.. should i have them order 2 and replace both? Or could my clutch on the fan just be going out?

the roadie
07-17-2009, 07:13 PM
If reports here are any statistic, fan clutches fail 50 times as often as relays.

tfrench91223
07-17-2009, 10:45 PM
is there any way to test the actual fan clutch itself? I'm figuring the test for the clutch relay is the same for the low beam relay.. but i apparently have a failing low beam relay ne ways so that test is out of the question..

tfrench91223
07-18-2009, 12:25 AM
i previously had an issue where the wiring harness actually melted and i had to replace the wiring harness for my passenger side headlight.. what i have noticed lately is sometimes that headlight will go out and if i tap it with my hand it will come back on.. Is it possible that i have something in that wiring failing which casues both of my headlights to go out rather than the low beam relay?

WOOLUF1952
07-18-2009, 01:56 AM
i previously had an issue where the wiring harness actually melted and i had to replace the wiring harness for my passenger side headlight.. what i have noticed lately is sometimes that headlight will go out and if i tap it with my hand it will come back on.. Is it possible that i have something in that wiring failing which casues both of my headlights to go out rather than the low beam relay?

I had the same problem with a new bulb. The filament was loose in the bulb. Took it back to the store, they replaced it with a new one. It's been fine for over a year.

tfrench91223
07-18-2009, 01:43 PM
Well, I just took off the factory headlight.. The aftermarket harness that I had previously installed seemed like it was connected perfectly.. The wires were kind of loose.. I redid the wiring harness.. Hopefully this fixes my headlight issues.. I'm thinking because the wiring was off it may have been throwing off the other headlight and causing some issues somewhere.. Hopefully this fixes my headlight issues.. If not, its time to buy a relay.. As for the over heating issues.. I'm thinking the clutch on my fan is out..

Toti1972
10-30-2009, 03:21 AM
When I was in pilot training, at night, my instructor reached over and turned off the instrument lights and asked what I'd do. I calmly reached into my shirt pocket and pulled out a mini-maglight and held it in my mouth while I continued to fly the plane. He snatched it away and said, what next, wise guy. I pulled out mini-maglight #2 from a sleeve pocket. He snatched that. I pulled out my BIG maglight from my flight bag. He snatched that. I finally had to manage the plane's engine RPM and airspeed by reference to the engine and wind noise, not seeing any of the instruments. THAT was the lesson he wanted to teach me, not discover how many spare flashlights I was carrying within reach. :duh:

Chapau!!! :tiphat

rso67
07-18-2010, 12:29 PM
Ok, so Iím having the same problem, only my dim lights went off last night and they will not come back on for anything. I have checked all fuses and relays. Neither was the culprit! I am at a loss right now! I have only had this truck for about 1 month and it has been at my dealerís service shop for about two weeks already! Any insight on this issue would help greatly. Thanks in advance! :worried:

WOOLUF1952
07-18-2010, 02:30 PM
Have you tested the bulbs to make sure they are good?

You would not be the first to have both bulbs go out at the same time. :m2:

rso67
07-18-2010, 04:47 PM
Have you tested the bulbs to make sure they are good?

You would not be the first to have both bulbs go out at the same time. :m2:

I checked them visually and didn't see anything out of the ordinary, ill buy some and check it...thanks!

the roadie
07-18-2010, 08:47 PM
...I have checked all fuses and relays....The solid state relay used for the low beams can only be properly checked with a voltage source, like a 9V battery, and a meter. Somebody posts every month about "checking the relays" and all they're doing is looking at them to see if they're burnt or something. That's not enough.

Swapping 45 and 46 sometimes reveals a bad one, though. Those are the only two solid state relays of their kind in the vehicle.

Boricua SS
07-18-2010, 09:16 PM
Swapping 45 and 46 sometimes reveals a bad one, though. Those are the only two solid state relays of their kind in the vehicle.

thats what i did is swap them and my lows came on.. so i took it to the dealer because im still under warranty and i had to go in the back and tell the mechanic how to fix it??? crazy... 5 minutes later, i was driving off the lot with a new relay and lows back

rso67
07-18-2010, 09:52 PM
The solid state relay used for the low beams can only be properly checked with a voltage source, like a 9V battery, and a meter. Somebody posts every month about "checking the relays" and all they're doing is looking at them to see if they're burnt or something. That's not enough.

Swapping 45 and 46 sometimes reveals a bad one, though. Those are the only two solid state relays of their kind in the vehicle.

I tried the switch and what do you know, let there be light! Thanks a million!

Boricua SS
07-19-2010, 12:12 PM
I tried the switch and what do you know, let there be light! Thanks a million!

good deal.. love the trailvoy family of experts.. saved me hundreds of dollars...

2003TrailLBZ
08-07-2010, 10:28 AM
After monhs of the headlights not going out, the other night they went out again, came back on about 5 minutes later. Might have to go and pull the 45 & 46 again and check them out, maybe time for a switch.:undecided

sci68
09-19-2010, 10:28 AM
My 03 envoy driver low beam is out, the passenger low beam is working. At times it would come back on from driving, other times I would bang the headlamp housing to rattle it a bit and it would stay on :confused: obviously a loose wiring or connection.....It is now out. I checked/switched fuses 3 and 6, no change in low beams (driver out, passenger on). I was thinking of switching 45 and 46 however since the passenger low beam is working, is it safe to assume the relay is fine?

Next step for me is to pull headlamp, check wiring connections and lowbeam bulb.

the roadie
09-19-2010, 11:14 AM
...since the passenger low beam is working, is it safe to assume the relay is fine? ...Yes, the relay is fine. Time to break out the voltmeter. You have the right to troubleshoot without a voltmeter. If you do not have a voltmeter, one will be provided you at low cost at Harbor Freight. Any troubleshooting you do without a voltmeter may be used against you in a court of law. You have the right to have the voltmeter present during troubleshooting. :woohoo:

christo829
09-19-2010, 11:15 AM
My 03 envoy driver low beam is out, the passenger low beam is working. At times it would come back on from driving, other times I would bang the headlamp housing to rattle it a bit and it would stay on :confused: obviously a loose wiring or connection.....It is now out. I checked/switched fuses 3 and 6, no change in low beams (driver out, passenger on). I was thinking of switching 45 and 46 however since the passenger low beam is working, is it safe to assume the relay is fine?

Next step for me is to pull headlamp, check wiring connections and lowbeam bulb.

Based on your description, it sounds like the bulb or the connector. Since the relay
controls both low beam headlights, if it was going, I'd expect both lights to go out.
Check the connector for corrosion or possible melting.

Good Luck!

Chris

sci68
09-19-2010, 02:31 PM
I changed the bulb, now the daytime lamps on the both driver and passenger lights do not work!!!:mad: Both lights work when I turn the lights on, why would the daylime running lamps now not work? Is it possible I now blew the relay? Recheck the fuses and relay? Thanks again!

sci68
09-19-2010, 02:57 PM
Well I switched out fuses 3 and 6 and 45 and 46 and still the daytime running lights do not work however the low beam llights work when I turn them on......:confused:

Thanks!

the roadie
09-19-2010, 03:11 PM
If the low beam lamps come on when you turn the switch to force them on, then the relay is good. What's missing now is the control from the BCM to the relay that turns them on at 70% intensity for the daytime. That could be a problem with the BCM or the light sensor that tells it that it's daylight. At least you know the wire from the BCM to the relay is good because that's what turns them on full using the switch. (In contrast to older vehicle designs, the lamp control isn't directly from the switch.)

sci68
09-19-2010, 03:24 PM
What's missing now is the control from the BCM to the relay that turns them on at 70% intensity for the daytime. That could be a problem with the BCM or the light sensor that tells it that it's daylight. At least you know the wire from the BCM to the relay is good because that's what turns them on full using the switch. (In contrast to older vehicle designs, the lamp control isn't directly from the switch.)

Forgive me Roadie, what is BCM? And where can I check the BCM or the light sensor? :thx

the roadie
09-19-2010, 03:27 PM
Body Control Module. Difficult to check without full schematics and/or a GM tech II tool.

WOOLUF1952
09-19-2010, 05:24 PM
To sci68:

I may have missed it in your description.

However, you do know the DRL's are not on in park, right?

sci68
09-20-2010, 07:41 PM
To sci68:

I may have missed it in your description.

However, you do know the DRL's are not on in park, right?


The DRLs are would always turn on either when I disengage the alarm or when I start the car and it is in park. It's been that way since I drove it new off the dealer lot. Perhaps the alarm has something to do with it???

BTW, I rechecked the fuses yesterday, pulled them and put them back in, still did not work, then a couple of hours later when I went to take the car out, now they work <knocking on wood> Gremlins indeed, glad do not need to have the dealer diagnose:woohoo:

RayVoy
09-20-2010, 07:51 PM
To sci68:

I may have missed it in your description.

However, you do know the DRL's are not on in park, right?In PARK, with the parking brake applied.

The operating of the parking brake handle, provides a ground input signal to the BCM that commands the DRLs to off.

WOOLUF1952
09-20-2010, 08:28 PM
In PARK, with the parking brake applied.

The operating of the parking brake handle, provides a ground input signal to the BCM that commands the DRLs to off.


I don't use my parking brake. If the daylight is bright enough the DRLs are off until I take the shifter out of park.

I do have HIDs and did the capacitor mod, if that makes a difference.

RayVoy
09-20-2010, 09:19 PM
I don't use my parking brake. If the daylight is bright enough the DRLs are off until I take the shifter out of park.

I do have HIDs and did the capacitor mod, if that makes a difference.Chances are, it's the Canadian version that makes a difference.
We don't have the same switch as the US trucks. We don't have a DRL off position.
Just Auto, Park and Headlights.

If I'm in PARK (in the daylight) with park brake on, the headlights are off. Release the park brake and the headlights (DRLs) come on.

WOOLUF1952
09-21-2010, 01:51 AM
That's probably the difference.

This is from the '03 owners manual:

The DRL system will make your headlamps come on
at reduced brightness when the following conditions
are met:
The ignition is on,
the exterior lamps knob is in automatic
the light sensor detects daytime light, and
headlamp mode,
the transmission is not in PARK (P).

It doesn't mention the parking brake, but mine is American version.

Sorry for the :hijacked. Now back to the original topic.

Are you still with us sci68?

sci68
09-21-2010, 05:48 PM
Just read through and caught up, wow just over a @#$% bulb:crazy:

Anyway, I rarely engage the parking brake and as I mentioned when I disengage the alarm the DRL would come on. I will try it with the parking brake engaged and see if DRLs are off, the missus has the vehicle.

nmclarks
09-29-2010, 10:38 PM
Wife came home and said her headlights were out - but the hi-beams worked. Since there were two separate bulbs and two separate fuses involved, I figured it was something else, but checked them out anyway. Everything looked good.

As the wife began to whine about how much this was going to cost to get fixed :bonk: - I began my search of this site. Found this thread, and post 27 (http://forums.trailvoy.com/showpost.php?p=760396&postcount=27) gave me something to try. I went out - and sure enough - it was sneaky relay #46!!!

Thanks to everyone who contributes to make this site so useful. :thumbsup:

Bob

fzkey
10-18-2010, 07:12 AM
So, could something like a weak battery cause the relay to give out.:undecided

the roadie
10-18-2010, 08:04 PM
So, could something like a weak battery cause the relay to give out.:undecidedNot a chance.

85TA406
10-18-2010, 08:22 PM
I have the exact same issue. Both lows stop working, wife pulls over, turns it off for a little while, starts truck, then they start to work. It has done it 3 times so far. Not cool. I guess I'll hafta try the relay swap.

Gord
10-21-2010, 01:18 PM
Thanks guys! Had the same headlight issue, tried the relay swap and it's the relay. Off to the dealer for a new one. :)

slewis80
02-16-2011, 11:35 PM
I must say thank you all!! This just saved me a couple hundred dollars from some mechanic that wouldve just told me to replace my relay!!!:woohoo:

broncoman94706
03-14-2011, 10:55 PM
Me too! Thanks a Million! I switched the fan clutch relay with the head light relay and the low beams came on. I then went to O'Rileys and ordered a 34.99 relay. I was glad to pay only 34.99 instead of a couple of hundred!

ric
:iagree:

Loverotties
03-15-2011, 12:44 AM
Got mine 6 months ago at auto zone for half that and got a 2 yr. warranty.

socaldooley
03-16-2011, 04:58 PM
Me too! Thanks a Million! I switched the fan clutch relay with the head light relay and the low beams came on. I then went to O'Rileys and ordered a 34.99 relay. I was glad to pay only 34.99 instead of a couple of hundred!

ric
:iagree:

I agree. Thanks to this thread I tested my relay, determined it was bad and found a replacement at Pep Boys. It all took maybe 15 minutes. Thanks so much for posting the problem and solution!

ajcarp
03-18-2011, 06:53 PM
Just wanted to say a quick thanks to all those who posted the troubleshooting info about swapping the relays 45 and 46 to test for a bad low beam relay...

Sure enough, when I swapped them, my low beams came on just fine. I'm now off to order a new relay!:)

WB Blazer
09-20-2011, 01:16 PM
I had the same thing happen about a month ago and replaced the #46 relay and the problem was solved. But, now it's happening again... Could it be a short? I did the 45 & 46 swap test again and, sure enough, the lights came on. There's no way a relay should go out that fast though. I noticed a burnt smell coming from 46. Another thing I noticed, the high beams don't work either this time, which is even more confusing. Definitely don't want to keep replacing expensive relays. Gotta be a short somewhere, right?

the roadie
09-20-2011, 01:41 PM
Shorts in wiring harnesses usually blow fuses because the current goes sky-high. A lamp that's partially failed internally could draw extra current, which *could* be enough to damage a relay but not blow the fuse.

What this is NOT is a traditional wiring-based short circuit, unless you have blown fuses as well.

There is ONE fuse per headlight, but the low beam pair and the high beam pair share a relay each.

To troubleshoot your current problem to a firm conclusion, you need a meter and some experience running it in current as well as voltage mode. You have that?

quicksilverado
02-05-2012, 10:54 PM
I had the problem with headlights randomly going out. Tried replacing fuses, relays, and light bulbs. None of these solved the problem. Had a local shop look into the problem. They did a search on a mechanics info board and tried a solution others have used. They removed all grounds and cleaned the connection points. This was about 18 months ago. Happy to say that solved the problem. No trouble since. This is a fairly common problem with newer vehicles. On GM f-bodies, corvettes, trucks and many other vehicles have had major problems that are pcm and bcm related are due to bad ground connections. There are several ground points and only one with a bad or loose connection can cause major electrical problems. It would be nice if someone could sticky this info.

ColtraneXL
05-17-2012, 12:20 PM
My lights just started this after my plug wires were replaced. The fuses are good so I will be going out to buy a new relay. This is great advice.:thx

zavesm
05-18-2012, 11:28 AM
I had the same problem on my 2003 XL, only it occurred at night. Under hood relay was the issue, and man are they expensive. I changed it and haven't had a problem since.

gmcee
06-16-2012, 11:56 AM
My low beams went out last night when I turned on the climate control. Needless to say, it's a little disconcerting at 75mph on a dark interstate (although much worse circumstances can be imagined). Fortunately, I had the presence of mind to immediately hit the high beams and there was light, so I got safely over to the side of the highway, shut off all accessories, and pulled fuses. Everything looked fine. Called my wife and let her know that I'd be late. All in all, probably was shut down for maybe 15 minutes. Re-started without A/C and low beams were on again. Drove another 10 miles this time with no A/C, then all of a sudden, no low beams again. I tried another shut-down of maybe 20 minutes but low beams would not come back on. Ended up driving 100 miles on fog lights (never used much before but now happy to have them) and high beams in order to get home.

So this morning, I'm on Trailvoy doing a search for "low beams" and now I've got answers. I really don't know how anyone can afford to drive one of these trucks without the info from this site. It sure has kept me out of the dealership's service department. :thumbsup:

Will try the relay swap today and report back.

Loverotties
06-16-2012, 03:31 PM
My low beams went out last night when I turned on the climate control. Needless to say, it's a little disconcerting at 75mph on a dark interstate (although much worse circumstances can be imagined). Fortunately, I had the presence of mind to immediately hit the high beams and there was light, so I got safely over to the side of the highway, shut off all accessories, and pulled fuses. Everything looked fine. Called my wife and let her know that I'd be late. All in all, probably was shut down for maybe 15 minutes. Re-started without A/C and low beams were on again. Drove another 10 miles this time with no A/C, then all of a sudden, no low beams again. I tried another shut-down of maybe 20 minutes but low beams would not come back on. Ended up driving 100 miles on fog lights (never used much before but now happy to have them) and high beams in order to get home.

So this morning, I'm on Trailvoy doing a search for "low beams" and now I've got answers. I really don't know how anyone can afford to drive one of these trucks without the info from this site. It sure has kept me out of the dealership's service department. :thumbsup:

Will try the relay swap today and report back.
You can only know by killing the DRL or wait till tonight,Because only daylights work during the day(Different circuit then low beam) or go in a dark garage.

gmcee
06-17-2012, 12:35 AM
Swapped around the relays tonight and low beams worked. Then replaced the faulty one with a $35 BWD part# R6100 from Advance Auto. All seems to be functioning normally...time will tell! :thumbsup:

mavericknj
01-30-2014, 01:43 PM
Thanks for all the research. Replaced the relays for the low beams and they worked fine. Saved a lot of diagnostic time and money. The wife and kids are happy.:)