Fan clutch diagnostic [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Fan clutch diagnostic


2002BlkLTZ
11-07-2005, 04:23 PM
I'm wondering, how to know for certain the fan clutch is gone? I have a 2002 with appx 46,000 on it (textbook for fan clutch failure!) and I've noticed a gradual drop in fuel mileage. I used to average around 14.5 (as high as 16, as measured by tracking gallons of fuel consumed and miles traveled). I have recently dropped to a steady 12.5 or so. I haven't noticed a constant "whoosh" sound from under the hood, but have occassionaly thought it sounded a bit loud. Is there any way to know for certain? Should the clutch spin freely when the engine's totally cold? I'm fairly certain it's gone/going but I'd rather not shell out the $200+ to replace it if I can avoid it. Also, has anyone used an aftermarket fan clutch, from a place like autozone, versus an OEM?

MikeLTZ
11-07-2005, 05:55 PM
if it went you would know it. The truck will seem to lack power. Also anything above 3k rpms sounds like a supercharger or a plane taking off. If it's not loud its proably ok.

Mine died on my 02 LTZ at 40k

bmm354
11-07-2005, 06:08 PM
Based on what I've heard when the clutch fails it usually fails in the on mode, meaning the fan is on all the time. There is no mistaking this as it is LOUD, like a jet taking off when you hit the gas. It will usually throw an error code too, because the fan clutch is controlled by the PCM (powertrain control module).

For this reason I don't know if there are even any aftermarket units available; it's electronic and rather tightly integrated with the computer. Plus there is an updated OEM part that should be used. Along with the new part there is a software flash upgrade for the PCM.

There are some tests you can do yourself:

-Rotate the cooling fan 3 complete revolutions.
The resistance of the cooling fan clutch should be even throughout each rotation. There should be no binding.

-To force the clutch to engage as a test:

The cooling fan noise should increase as the cooling fan clutch engages. It can take up to 2 minutes for full cooling fan clutch engagement. If cooling fan clutch is previously fully engaged, then there will not be a noticeable change in cooling fan noise.

Important
DTC P1482, for 4.2L (LL8), and P0480, for 5.3L (LM4), will set when the cooling fan relay is disconnected.


Turn OFF the ignition.
Disconnect the coolant fan relay.
Connect a 10-amp fused jumper wire between the cooling fan clutch supply voltage circuit of the cooling fan and the ignition 3 voltage circuit of the cooling fan relay.
Start the engine.
Raise engine speed to 2,000 RPM for 2 minutes.
Does the cooling fan clutch engage?

Yes - Force clutch off as a test
No - need scan tool to test further (meaning, a trip to the dealer)

-------------------------------------

To Force clutch off as a test:

Important
Continuous excessive fan noise is due to a mechanical failure. If the fan noise decreases during this step, then there is an electrical malfunction. Replacing the cooling fan clutch will not correct the condition.


Turn OFF the ignition.
Remove the 10-amp fused jumper wire.
Install cooling fan relay.
Disconnect the cooling fan clutch connector.
Start the engine.
Raise engine speed to 2,000 RPM for 2 minutes.
Does the cooling fan disengage?

Yes - OK
No - need scan tool to test further (meaning, a trip to the dealer)

autotech
11-07-2005, 09:34 PM
if you have the factory original fan clutch on a 2002, you should replace it if you are having doubts. just be sure to have the most recent part number and most recent calibration installed in the vehicle. but thats just my professional opinion, take it or leave it.

2002TBNJ
11-14-2007, 06:28 PM
Hello all... I have a 2002 TB LTZ with 64,000 miles on it. I've noticed lately that when I first start the truck the fan sounds like a jet engine. I drive up a steep incline right away after starting the engine and it really sounds like a jet engine as I go up. Is this normal for this specific engine? It does calm down after the engine gets a bit warm. Is this a clutch fan issue cause I still have 2 months left on the extended warranty?

Thanks and PS. This is a great site that I'm sure I'll be grateful for in the years to come.

Thanks again

Billy

rbarrios
11-14-2007, 06:43 PM
2002TBJN- use that warranty to get that clutch replaced.
out of warranty can run you anywhere from 400 to 600 depending on who works on your vehicle. your being a 2002, its not a question of will it fail... but WHEN....
normally the fan clutch in the mornings are engaged because the fluid in the clutch has settled down to the bottom.
as the vehicle runs for a bit the fluis should distribute, and the loud noise will go away.
Also- how long do you wait for your engine to run before dring away up that hill?
on my vehicle, I turn it on, get the loud swooshing for about 3-5 seconds and then I can hear it get softer and then the noise is gone- I ALSO allow the engine RPM's to drop below 1000.... meaning that once its in the 800 to 950 range, thats when ill shift into drive or reverse.

2002TBNJ
11-14-2007, 09:26 PM
Thanks for the quick reply. I usually let the truck idle for about 1 minute or more to get the RPM's down to 1000 then i'll make a quick left and head up the hill and that's where it sounds like a jet engine. After a few minutes of driving the whine starts to go away. I'm actually getting a belt whine and a loud chirp every once it a while now. I'll bring it in to a dealer and see what they think.

thanks

Billy

2002 TB LTZ

Landis
12-20-2007, 10:58 AM
To Force clutch off as a test:

Important
Continuous excessive fan noise is due to a mechanical failure. If the fan noise decreases during this step, then there is an electrical malfunction. Replacing the cooling fan clutch will not correct the condition.


Turn OFF the ignition.
Remove the 10-amp fused jumper wire.
Install cooling fan relay.
Disconnect the cooling fan clutch connector.
Start the engine.
Raise engine speed to 2,000 RPM for 2 minutes.
Does the cooling fan disengage?

Yes - OK
No - need scan tool to test further (meaning, a trip to the dealer)

I would like to perform this test on my vehicle as my 2003 Envoy fan is in the stuck on position and has not disengaged in 5 days. I would like to see if it is not electrical before I go out and buy the fan clutch to replace.

However I have a question to the above test. Where is the 10-amp jumper wire? Where is the fan relay (and is that buy and install a new fan relay)? Where is the cooling fan clutch connector?

Do I need to remove anything to get to these parts like the radiator? Thank you, I appreciate any guidance.

Jeff

AbsoluteZero
12-20-2007, 02:50 PM
While failing in the "on" condition may be the norm, my condition was I could literally count the fan blades as it turned when first started. So little air was moving thru the condensor the compressor would cycle off because of high head pressure. It was replaced under extended warranty. Now it comes on full for a minute or so but moves a lot of air. No more compresor cycling because of high head pressure.

tblazed
12-20-2007, 03:33 PM
Where is the fan relay (and is that buy and install a new fan relay)? Where is the cooling fan clutch connector?


Jeff

The jumper is from another part of the test to power on the control valve to make the fan engage fully. Disregard that part for now.

You can test if the clutch will disengage by pulling out Cooling Fan relay #45 or pull #20 Cooling Fan fuse.

The connector is on the driver side upper corner of the fan shrowd.

Landis
12-20-2007, 04:16 PM
The jumper is from another part of the test to power on the control valve to make the fan engage fully. Disregard that part for now.

You can test if the clutch will disengage by pulling out Cooling Fan relay #45 or pull #20 Cooling Fan fuse.

The connector is on the driver side upper corner of the fan shrowd.

Thank you. Pulled the #20 fuse for the fan relay, fan still came on as before. I guess I need to bite the bullet and get a new fan clutch. I will probably do the install myself. I have heard people say that a computer update is needed after. I will do that too.

tblazed
12-20-2007, 04:29 PM
Thank you. Pulled the #20 fuse for the fan relay, fan still came on as before.. Came on, but how long did you let it run? My old clutch used to take several minutes sometimes to disengage. If my new clutch comes on enaged at startup it will disengage in about a minute, or less sometimes.


There are a lot running new clutches without the update. Nice to have, but not critical. I finally got mine updated with the PCM tune.

Landis
12-20-2007, 05:22 PM
Came on, but how long did you let it run? My old clutch used to take several minutes sometimes to disengage. If my new clutch comes on enaged at startup it will disengage in about a minute, or less sometimes.

I let it run for about 5 minutes. Even held it at 2000 RPM for 2min. This was only with fuse#20 out. The relay#45 was left in.

VILeninDM
01-10-2011, 01:38 AM
hey everyone. I know this is an old thread, but I have a very related question so instead of asking it again, I figure might as well continue this one...

I have 2002 TB (one of the first ones from the assembly line). I just took apart a whole bunch of things to get to A/C clutch bearing and while doing so noticed that it takes more effort than what I would have expected to turn the fan while the clutch (fan clutch, not related to a/c) is disengaged.

I don't hear the typical crop duster blowing when the clutch is fully engaged, but it feels like whatever fluid is between the fan and the shaft has gunked up and became much more viscous than it previously was.

Is this a sign that while I have the fan out of the car, I might as well replace the clutch?

smokeurtires
03-11-2011, 12:24 PM
OK, so I pulled the relay and # 20 -10 amp fuse ( still ok ). I went for a drive no excess fan noise, and the power is back.:thumbsup: Does this mean my relay is shot, not sure on the concept, usually when something is toast ( fuse etc. ) whatever is down the line will not function.
Thanks


The original fan clutch was replaced 2 yrs ago.

the roadie
03-11-2011, 12:39 PM
The relay is a solid state (electronic) unit, and (as opposed to the normal mechanical ones) one of the possible failure modes is for it to be locked on. Swap with the adjacent one that looks the same that's for the low beam headlights if you want to diagnose it for sure.

klguy77
07-11-2011, 11:46 PM
Ok guys, I have a problem with my 06 Trailblazer 6 cylinder. For a while now i have been hearing that wooshing sound from my fan and didnt really think anything of this since its been doing it since i bought the thing, but today I started to hear a clunking/grinding noise coming from the front of the engine. When i looked at it, it was coming from the fan up front. I shut the truck off and i shook the fan clutch, it felt pretty lose along with where it connects. While running i can see the fan wobling along with that noise. I need to fix soon and i think its the fan clutch. Does this sound about right? Also had a problem with the speed 5 for the ac not working, i replaced the resistor since the ground wire and wire for speed 5 looked melted. That fixed it but after i started it the second time it went back out. Not sure if these r related problems or not, just trying to give as much infor as possible.

the roadie
07-11-2011, 11:52 PM
The water pump contains the bearing that's loose, so you need to change the water pump. Might as well change the fan clutch while you're in there if you don't trust it.

The HVAC blower issue is not related, and you just need to change the wiring harness / connector if it's damaged.

klguy77
07-12-2011, 12:00 AM
Thanks man, that was quick. I was planning on trying to repair this tomorrow. Anything special i need besides a torque wrench and the fan clutch wrench.

Bay Wolf
07-12-2011, 02:20 PM
I rented the fan clutch set from 3 different places. None of them would hold properly. If you have an air compressor, an air hammer/chisel will save you a lot of time and effort.

klguy77
07-12-2011, 05:14 PM
yea i had to rent it from 2 different places in order to get the right one. Im having a problem putting the lower tranny lines back in, see i took them out from the radiator and now i cant get them to thread back in. Looks like the mating part to the line has dipped a little in the radiator and i just cant seem to get it to go. Anybody know how to get this threaded. This is all i have left to do with the exception of topping fluids and test drive. PLEASE HELP!!!!:suicide:

klguy77
07-12-2011, 05:35 PM
well, i talked to someone and they told me ill have to buy a new radiator, which is hard to believe. If there arent any tricks to getting it back in, should i take the radiator out and disconect the quick connect and try to install it that way. Seems like if i held the radiator just right i would be able to thread it. I just wish i know those lines had a quick connect. That would of saved me a lot of time and money since i lost a lot of tranny fluid.:bonk:

klguy77
07-13-2011, 11:38 AM
Alright, I got it! shes running like a dream now even though it took me a while since i didn't use the quick disconnect. I had to take everything back off and take out the radiator. While holding it on its side i was able to thread both connectors back in. After putting it all back together their was no leaks!

Note to anyone replacing the fan clutch or water pump, don't be a dummy, use the QUICK DISCONNECT!!!!!

cdufour9
02-16-2012, 11:30 PM
2004 Envoy XL 5.3L
177,000 KM
Found someone else with the same story as me.
The fan would spin with the engine RPM. at all speeds. loud roar sound. would settle down at highway speed, RPM would hang around 1600.
stayed like this for a week.
Came back normal for few days.
Today, stepped on the gas to access on ramp and KABLAM !!! pieces flying everywhere. Nice big prune in the hood. Engine shut itself down, pulled over. Popped the hood, fan blade, fan blade cover nowhere to be seen. Fan clutch hanging at the bottom, water pump had a 5"x4" whole, coolant leaking out.
The boys at the shop had a reunion around the truck. They had never seen that. Was quoted $3300 at Canadian Tire. That's only after installing: new water pump, radiator, fan, fan clutch, fan cover including labour. Wires near by may throw up codes afterwards if they got kingked in the event. More $$.

The fan clutch that gave up on me, was just 9 months old. It was a Dorman from rockauto.com at 130$ plus shipping. Should I of went with AC Delco ?

If your fan clutch gets stuck engaged. Don't postpone the repair.
Not the cheapest job but you do the math.

Anniversaryss
07-22-2014, 05:08 PM
Based on what I've heard when the clutch fails it usually fails in the on mode, meaning the fan is on all the time. There is no mistaking this as it is LOUD, like a jet taking off when you hit the gas. It will usually throw an error code too, because the fan clutch is controlled by the PCM (powertrain control module).

For this reason I don't know if there are even any aftermarket units available; it's electronic and rather tightly integrated with the computer. Plus there is an updated OEM part that should be used. Along with the new part there is a software flash upgrade for the PCM.

There are some tests you can do yourself:

-Rotate the cooling fan 3 complete revolutions.
The resistance of the cooling fan clutch should be even throughout each rotation. There should be no binding.

-To force the clutch to engage as a test:

The cooling fan noise should increase as the cooling fan clutch engages. It can take up to 2 minutes for full cooling fan clutch engagement. If cooling fan clutch is previously fully engaged, then there will not be a noticeable change in cooling fan noise.

Important
DTC P1482, for 4.2L (LL8), and P0480, for 5.3L (LM4), will set when the cooling fan relay is disconnected.


Turn OFF the ignition.
Disconnect the coolant fan relay.
Connect a 10-amp fused jumper wire between the cooling fan clutch supply voltage circuit of the cooling fan and the ignition 3 voltage circuit of the cooling fan relay.
Start the engine.
Raise engine speed to 2,000 RPM for 2 minutes.
Does the cooling fan clutch engage?

Yes - Force clutch off as a test
No - need scan tool to test further (meaning, a trip to the dealer)

-------------------------------------

To Force clutch off as a test:

Important
Continuous excessive fan noise is due to a mechanical failure. If the fan noise decreases during this step, then there is an electrical malfunction. Replacing the cooling fan clutch will not correct the condition.


Turn OFF the ignition.
Remove the 10-amp fused jumper wire.
Install cooling fan relay.
Disconnect the cooling fan clutch connector.
Start the engine.
Raise engine speed to 2,000 RPM for 2 minutes.
Does the cooling fan disengage?

Yes - OK
No - need scan tool to test further (meaning, a trip to the dealer)

Hope your still around. Well I replaced my fan clutch which I now believe was incorrect and it was the new one was stuck engaged (jet engine engaged lol). So I did a version of what u said to get the fan to disengage and it us no longer engaged. I'm not sure of its functionality but as long as it doesn't sound like a jet I'm fine with it. But now I'm back to square one I get th P0526 code for fan sensor. Where do I go from here.

Anniversaryss
07-22-2014, 06:29 PM
I did a voltage check on the harness. Not the harness from the clutch but the harness that I assume comes from the the computer . Some research said that to find out eat the colors mean and I found out the five wires one is ground I'm getting 12 volt one is a reference voltage from pcm I get five volts another is for the fan speed I get 5 volts another is also a fan reference I get 5 volts but one wire called the low reference wire I do not get 5 volts. If this helps please help me lol

Scott neprud
09-25-2014, 08:58 PM
Ok guys, I have a problem with my 06 Trailblazer 6 cylinder. For a while now i have been hearing that wooshing sound from my fan and didnt really think anything of this since its been doing it since i bought the thing, but today I started to hear a clunking/grinding noise coming from the front of the engine. When i looked at it, it was coming from the fan up front. I shut the truck off and i shook the fan clutch, it felt pretty lose along with where it connects. While running i can see the fan wobling along with that noise. I need to fix soon and i think its the fan clutch. Does this sound about right? Also had a problem with the speed 5 for the ac not working, i replaced the resistor since the ground wire and wire for speed 5 looked melted. That fixed it but after i started it the second time it went back out. Not sure if these r related problems or not, just trying to give as much infor as possible.


How bad was your fan wobbling????? Mine has been doing this for a week or so now and I'm not sure if I have a warped fan or if its the clutch or the bearing in the water pump. Any kind of help would be greatly appreciated.

ylab
09-26-2014, 08:53 AM
I have the genuine GM Clutch, Fan and Shroud that came off my Envoy, when I went to e-Fans. It was a replacement under the extended warranty a few years back and rather than having to make the repair out of warranty, I moved to e-Fans.....who am I kidding, I wanted to free up the 12-15 hp and used that and the 2 mpg average increase as an excuse.

If you need either, make me an offer, they worked fine when removed. (I'll sell it cheap, parted with the Envoy in August). Don't know what part number they put on, just know it fixed the locked in jet turbine mode. - Although an occasional start at high speed from the fan resting with the valve downward is normal, IF it slows when you accelerate or rev the engine above 2k. (It should never grind or clunk).