Can Grounding Issues Affect Lighting and Trailer Brake Functions on 2001 GMC Sierra 2500 HD

Question

Question:

Hardwired an LED Firestrip to my Auxiliary trailer lights port on my truck. Now when I plug in my trailer lights, my left turn signal causes my right turn signal to also pulse on my trailer. I also get an Error on my trailer brake controller now too. Could this be because my trailer lights are incandescent? I am positive the Firestrip is wired properly Left turn, Right turn, Brake, and Ground. Wiring Diagram Incoming Auxiliary Power []Auxiliary Trailer port Firestrip. I also had an amp installed for speakers, could this be a grounding issue caused by the amp?

asked by: Jacob F

0

Expert Reply:

Your recently installed audio amplifier should have no interaction with the vehicle or trailer lighting since it should be directly connected only to the battery +12V and ground. There should be no common wiring between the audio and lighting systems. Your trailer lights being incandescent should have no bearings on this issue.

What is the error message on your trailer brake controller? If it indicates that it has lost connection to the trailer brake circuit then there could be a corrosion issue within the connectors or a bad ground on the truck or trailer harness.

A loose or corroded main ground connection can cause all sorts of issues with trailer lighting, including weird behavior like what you describe. I suggest making your first step a check of the main ground wires for the truck's and trailer's harnesses. These ground connections need to be made to a clean bare metal surface, free of rust, grease, paint, primer, etc. Try sanding off the ground points on the truck and trailer frames and re-connecting the ground wire ring terminals. Dielectric grease like # 11755 helps protect those new clean connections.

Also check all wiring connectors for signs of discoloration or corrosion. Sometimes corrosion will develop inside a connector housing where it can be hard to spot. This issue can easily cause shorts between adjacent circuits that could lead to issues.

If the grounds and connectors are okay I suggest disconnecting the light strip and testing the trailer light and brake functions again.

expert reply by: Adam R

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Answer 1

My suspicion is that you have a poor ground connection somewhere on your trailer. The fact that everything works fine until the running lights are turned on is the dead giveaway. When the tail lights are turned on, the trailer lighting is drawing…

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Answer 2

The number on the lens is not a part number. It is a rating for the lens/light. Based on that number it looks like the best match we have is #A31RB which is rated SAE AP2 86. The A in the number just means that it has a built-in reflector.

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Answer 3

it sounds like you have a ground problem somewhere in the trailer wiring or on the trailer wiring harness installed on the vehicle. Ground problems will make the trailer lamps do all sorts of wacky things. With the running lights and the brakes on,…

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Answer 4

You said you checked the brake magnets. When inspecting them did you notice if the windings inside the magnets are showing? If so this is most likely the reason that the short is showing up on the controller when the vehicle is moving. This would…

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Answer 5

The controller is only putting out voltage when the manual switch is applied on the brake controller, but not when the vehicle brakes are applied, is that correct? The most likely problem is that the controller is not getting the input that the…

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Answer 6

To wire your electric brakes you will want to run 10 gauge wire #10-1-1 to one of the brakes and run it to the other brake, using butt connectors like #05732-2 to connect them. The grounds will not be spliced, each brake assembly should have its own…

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Answer 7

You are correct, you should only be getting output when the brake is applied, or the override switch is activated. It sounds like the controller might be bad, but to make sure, you should probably bench test it before tossing it. Use a circuit…

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Answer 8

It depends on what the brake controller output is set to. If you have the brake controller set to the maximum then there should be about 12 volts at the brake magnets. To see if the brake magnets are drawing the correct power set the brake controller…

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Answer 9

Your brake lights and turn signals for each side are on one circuit. The left side turn signal and brake light is generally the yellow wire going into your trailer connector. The first thing to do is check the fuses on your tow vehicle. Next, inspect…

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Answer 10

There are a number of reasons why the brakes on your trailer may not be working. Lets start with the easiest things to check. First, check the vehicle and trailer connectors for corrosion. This can cause a short inside the connector and the brake…

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Answer 11

On both a 7-Way and 4-Way trailer connector the brake lights and turn signals are on the same circuit so it is strange that the brake lights aren't working. But, brake lights draw more constant power than the running lights or the turn signals so…

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Answer 12

The circuits related to your brake controller and the trailer lighting are actually totally separate. If you are blowing trailer lighting fuses on your truck the brake controller shouldn't be affected at all. The only circuit they may share is…

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