# Trailer Stop/turn/hazard Light Problem



## Leedek (Nov 28, 2010)

If you have a problem with your trailer lights then this may be what is causing it.









I own a 2003 Silverado and found that when I have my trailer hitched, my right brake light fails to light. I found that the trailer has a two-filament bulb. One filament is for "running" lights and the other filament lights for "hazard", "turn", and "brake" indications. My right brake light was not lighting but the hazard and turn signals functioned correctly. With indications like that I knew that at least the bulb assembly was properly grounded, as the light did light. I even had a buddy with a different truck hook up to the trailer. His truck operated all functions of lighting. So that left me with my Silverado.

On the drivers side of the dash is a fuse block






with most of the trailer fuses. The panel covering the fuse block can easily be removed when the driver's door is open.






It is important to check each of these fuses to ensure your problem is not just a blown fuse. 10 Amp fuses for trailer RT light, LT light, RT brk/trn/emg , and LT brk/trn/emg are easily checked.

My problem was the *LCM (Light Control Module aka Turn Signal/Hazard Flasher Module). *To get to it you have to remove the knee bolster panel below the steering wheel. To remove the knee bolster you first need to remove the instrument bezel. (Do not be put off by this procedure. It is quite simple and you will not damage your truck.)

BEZEL REMOVEL PROCEDURE:







1.	Apply the parking brake to prevent the vehicle from moving.
2.	If equipped with an automatic transmission, move the shift lever all the way down to the last gear.
3.	Tilt the steering wheel to the full down position.
4.	Pull gently rearward on the corners of the bezel from the instrument panel (IP) assembly.
5.	Remove the bezel.

KNEE BOLSTER REMOVAL PROCEDURE:
1.	With the bezel removed you can remove the two knee bolster screws at the bottom edge of the bolster.







2.	Unsnap the top of the knee bolster from the IP assembly.
When you have the bolster removed you will be able to see the 2/4-W/OPT. TRAILERING relay assembly; GM p/n # 15764135. The module is directly behind the fuse box at the bottom of the box (the fuse box faces towards the driver's door, and the LCM faces towards the steering column). To remove it pull it straight out towards the steering column (it is black in color, has 10 blades, slides in and out like a fuse would and the end you can see measures 1" x 2-3/4").

Once removed you will see the module has a plastic outer cover held in place with a tab/slot configuration. A small flat blade screwdriver can be used to open the module up to "repair" it or you may wish to purchase a new one from GM for $97.00 or NAPA has suitable substitutes at around $50.00. I choose to see what was inside the case






and managed to repair mine. Years ago most auto mechanics and electronic technicians routinely repaired multi-contact relay assemblies. This module is really nothing more than a relay assembly with micro circuits controlling its operation. If you have a burnishing tool in your toolbox then all that is required is a delicate touch up of the contact surfaces of the relays. If you do not have a burnishing tool then a slip of bond paper ( that paper in your printer tray) can be substituted. A little isopropyl alcohol is a good agent to use in contact cleaning. Gently function the relay contacts together manually with the bond paper between them. Pull the paper through the contacts a couple of times to clean/burnish them.

NOTE: A file from your workshop is *NOT *a good tool for this job. The contacts are very small and the space very confining. When done just follow these instructions in reverse and viola&#8230; you're trailer lights work as they should.

I had this problem last year about this time. My burnished relay assembly is still working like a champ. During my web search for information I found out that there is a "LED Compatible LCM". I don't have LED stop/turn/hazard lights on my trailer so no need for it but if you upgraded and are having problems with lighting.... 'nough said.

Safe travels and c'ya down the road.


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## sonomaguy (Jun 17, 2012)

I found the box, opened it up, now how do I get a piece of paper way down inside there? Do I need to purchase the proper burnishing tool?


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## Leedek (Nov 28, 2010)

sonomaguy said:


> I found the box, opened it up, now how do I get a piece of paper way down inside there? Do I need to purchase the proper burnishing tool?


 
Paper slip..... check paper slip.
Forceps .... check forceps.
Isopropel .... check isopropel.
Dip it... check dip it.
Insert slip... check insert slip.
Pinch contacts closed.... check pinch contacts closed.
Repeat as needed... Ditto forever.








Pull out hair until relief shows up.


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## sonomaguy (Jun 17, 2012)

Leedek said:


> ]
> 
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> 
> ...


That is to funny, I am already bald.









Dang my nose looks big.


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## Dudaronamous (Aug 24, 2013)

Before reading this thread, I replaced the trailer bulb assembly, burnished all trailer wire connections, checked all fuses on my 2005 Tahoe, but still no left brake light on the trailer. Many thanks to Leedeck for posting the thorough instructions and photos. I replaced mine with replacement flasher part number 10383320 (about $27 from Amazon.com) and all my trailer lights work now. THANK YOU forum members!


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## Leedek (Nov 28, 2010)

Dudaronamous said:


> Before reading this thread, I replaced the trailer bulb assembly, burnished all trailer wire connections, checked all fuses on my 2005 Tahoe, but still no left brake light on the trailer. Many thanks to Leedeck for posting the thorough instructions and photos. I replaced mine with replacement flasher part number 10383320 (about $27 from Amazon.com) and all my trailer lights work now. THANK YOU forum members!


You are welcome my friend!







I am always delighted that someone finds my posts helpful. This particular problem has got to be pretty widespread. I beleive the truck service departments know the problem well but don't broadcast the fix. Thank you Dudaronamous; you made my day.


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