Trailer Brake Lights

[mwhitman]

Anyone had a problem with the trailer brake lights only working on one side. All running, signal lights work, however I only have 1 brake light (left). Without a schematic, it's difficult to trace all the wiring to find out where the switch over actually takes place. :crazy:

[the roadie]

That's one of those failures that shouldn't be possible, unless the body control module is fried. The lamp filament for the trailer brake light is the same one used by the turn signal, so that proves the fuse is OK. Assuming the turn signal works on that side. Is your warning flasher also missing on that side? I've got the schematic for 2004, but in this circuit, I don't see why they'd change from year to year.

[mwhitman]

I know what you mean. It's got me scratching my head!! All the lights on the SUV work fine. All the lights on the trialer work fine except right brake. I even switched the rear light holder on the truck thinking one might be bad. Same results. I checked the wire right at the trailer receptcal on the trck and still only one brake light. It's got me stumped.

[RayVoy]

Check it in a dark area, see if your getting a small amout of light from that bulb.

[mwhitman]

No light at all, All grounds are good as well

[rrbrosse]

Hi,

the signal for the trailer connector is going to the underhood fuse box Fuse 51 and 52. If you have the same weird behavior at this location, it is possibly the turn signal module. THis module is located under the dash, driver side, left cover panel. This module is a small 2 inch by 1 inch 10 pin. The part number is 12450284.

[the roadie]

Excellent idea, rrbrosse, and welcome to the forum! I just traced the schematic, and all the relevant signals go through the flasher module. If the brake lights and turn signals work on the truck itself, which use separate lamps, it's the flasher module that combines the signals together for the trailer lamp, which only uses one filament for the brake/turn function.

$25 plus shipping at parts4chevys.com, or $25 on ebay for a lot of two of 'em, and then you could sell the extra one here.

[afjfam]

Anyone had a problem with the trailer brake lights only working on one side. All running, signal lights work, however I only have 1 brake light (left). Without a schematic, it's difficult to trace all the wiring to find out where the switch over actually takes place. :crazy:

Just to be sure about this, the right turn signal works but the brake light on that side doesn't? What about if you have the turn signal on and press the brake, what happens then?

[rrbrosse]

Hi,

On my last post I was talking about the flasher module, because I had a problem with my lights at that time and I was suspecting the module.

My problem was, right brake not working, right flasher not working, left flasher was working but with the left flasher at the same time.

I tested the module right in the fuse box and it was them obvious that it was not the module, but something in the cabling going back to the trailer connector.

Actually the culprit was the ground pin at the back of the trailer connector. This pin was corroded. It is very simple to check.

1- Unplug the rear connector at the back of the trailer connector by pulling it while pressing the lock on it.
2- remove the trailer connector by pushing the small pin lock just beneath the connector ( this plastic pin is coming out of the metal bracket holding the connector and it is easy to see it) and turn the connector. It will come out very easely.

[pixle2001]

okay, i have read through all of these on here and I kind of get what everyone is saying, I have almost the same problem on BOTH of my trailers except all the lights work BUT the brake lights. I turn the running light's on and still no brake lights, what could be the the problem, I can't find the fuses for just the trailer brake lights in my manual.......any suggestion's before I spend money at the dealer plz

[the roadie]

There is no separate fuse for the trailer brake lights since they use the same filament in the lamps as the turn signals. There is only ONE trailer left turn signal wire, fused by underhood fuse 51. There is ONE trailer right turn signal wire, fused by underhood fuse 50.

I assume, but you didn't explicitly say, that both left and right turn signals work on your trailer.

When you hit the brakes, BOTH left and right turn signal wires go to 12 V, and that's under control of the flasher module, GM #12450284 and available at many aftermarket parts places. Just ask for the flasher module.

[mspicer]

I have a 2002 GMC Envoy SLT and have the same problem where the right brake light on the trailer does not work; however, the right turn signal works fine as well as all of the Envoy's lights. I disconnected the trailer and used a volt meter at the Envoy's trailer connector to determine that when the brakes are applied the voltage drops to zero for the right brake light but goes to 12v for the left brake light. When the right turn signal is used I get voltage to the right side for the turn signal at the connector.

After reading this post I purchased the flasher control module, GM #12450284 from my local dealer.

My problem is that when I take the lower cover off from the driver's side dash on the 2002 GMC Envoy SLT I am unable to locate the flasher control module.

Where do I find the module and is GM #12450284 the correct flasher control module for the 2002 GMC Envoy SLT? (The dealer parts agent was of no help)

Thanks in advance.

[the roadie]

Did you find my previous posts in a search where I mentioned the flasher module was available in the aftermarket? If you're going to a store with no help, you might as well pay less than at the dealer that was no help. ;)

I have no idea what your dealer stuck you with, or what vehicle that's supposed to work in.

The right one is GM or ACDelco #15231201

$38 from rockauto.com

Item #11:

http://www.compnine.com/largeimg/051222TS02-211.gif

[RayVoy]

The easiest way to find a flasher module.................turn it on and follow the clicking.