Trailer brakes not working

[Dave27]

Last year I had a problem with the "check trailer wiring warning in TV" that I posted on 1/11/2020. The resolution to it was installing a junction box to replace the "rats nest" in the pin box.This year we are traveling to the southwest for the winter. The message came back, only it is worse this time, the brakes aren't working! They will work sometimes, but it is not predictable. I went back to look at the suggestions from last year and searched the site for others with brake issues. This is what I've done so far, and none of them have solved the problem: I checked the wiring in the junction box and made sure all the connections were snug. I replaced the plug from the trailer to the TV (one of the clips collapsed together, rather than closing over the pin in the receiver). Suspecting a ground problem, I found a wire nut holding five ground wires together in the front storage compartment. They all seemed tightly twisted together, but as long as I was looking at it, I put all the ground wires on a circuit block and jumped them all together. I did a continuity test on the trailer plug between the ground and brake wire and got the welcome beep.

Today I hooked up the TV to the trailer while we are camped. The TV recognized the trailer, and I could hear the brakes buzzing when my wife pressed the brakes. I touched a couple of the wires coming from the axle and the brakes stopped working. I can't see anything wring with the wires. I moved the wires around with no effect. After turning the engine off, reconnecting the plug, we went through a number of trials of braking the TV. It seemed like a totally random process. Sometimes they worked, sometimes they didn't the next trial, without touching anything. Sometimes they stopped while the TV brakes were applied and nothing was touched. This is very perplexing, why would the brakes work sometimes and not others when we are parked?

What is the next step? I am thinking of taking the wheels off, but I'm not sure what I would be looking for. Any insights or suggestions?

thanks, Dave

[TucsonJim]

Last year I had a problem with the "check trailer wiring warning in TV" that I posted on 1/11/2020. The resolution to it was installing a junction box to replace the "rats nest" in the pin box.This year we are traveling to the southwest for the winter. The message came back, only it is worse this time, the brakes aren't working! They will work sometimes, but it is not predictable. I went back to look at the suggestions from last year and searched the site for others with brake issues. This is what I've done so far, and none of them have solved the problem: I checked the wiring in the junction box and made sure all the connections were snug. I replaced the plug from the trailer to the TV (one of the clips collapsed together, rather than closing over the pin in the receiver). Suspecting a ground problem, I found a wire nut holding five ground wires together in the front storage compartment. They all seemed tightly twisted together, but as long as I was looking at it, I put all the ground wires on a circuit block and jumped them all together. I did a continuity test on the trailer plug between the ground and brake wire and got the welcome beep.

Today I hooked up the TV to the trailer while we are camped. The TV recognized the trailer, and I could hear the brakes buzzing when my wife pressed the brakes. I touched a couple of the wires coming from the axle and the brakes stopped working. I can't see anything wring with the wires. I moved the wires around with no effect. After turning the engine off, reconnecting the plug, we went through a number of trials of braking the TV. It seemed like a totally random process. Sometimes they worked, sometimes they didn't the next trial, without touching anything. Sometimes they stopped while the TV brakes were applied and nothing was touched. This is very perplexing, why would the brakes work sometimes and not others when we are parked?

What is the next step? I am thinking of taking the wheels off, but I'm not sure what I would be looking for. Any insights or suggestions?

thanks, Dave

Hi Dave,

I think it's probably time to remove the wheels and hubs and inspect the brakes. Check the wiring from where it enters the backing plate to the brake magnets. Also check the magnets themselves. Or, it could be you have a wire with an intermittent open circuit. If that's the case, you may want to try running new brake wires. It's a pretty big job, but can probably be knocked out in half a day or so.

Jim

[Cate&Rob]

Dave27
Hi Dave,

There is often some intermittent “logic” in the TV application of trailer brakes when the truck is not moving. This has to do with not needing or applying the trailer brakes in very slow speed maneuvering. This can be over ridden with the hand apply of the brake circuit. Are results more consistent if the trailer brakes are applied in this way?

Another thought . . . do the trailer brakes apply consistently when the break away pin is pulled?

Rob

[Dave27]

Dave27
Hi Dave,

There is often some intermittent “logic” in the TV application of trailer brakes when the truck is not moving. This has to do with not needing or applying the trailer brakes in very slow speed maneuvering. This can be over ridden with the hand apply of the brake circuit. Are results more consistent if the trailer brakes are applied in this way?

Another thought . . . do the trailer brakes apply consistently when the break away pin is pulled?

Rob

Cate&Rob When driving and the trailer brakes aren't working, it doesn't matter if I use the manual brake control, no response from the trailer brakes. I just went outside and pulled the break away pin, the brakes were quiet. Those were good suggestions.

[howson]

Dave27

I suspect there's an issue with a wire back by the axles (chaffing or nearly broken). On an aircraft with a intermittent wiring issue we'd just run new wires along the bundle from the start to the end of the circuit. I'd try the same thing with the trailer brake wiring.

Howard

[Cate&Rob]

Cate&Rob When driving and the trailer brakes aren't working, it doesn't matter if I use the manual brake control, no response from the trailer brakes. I just went outside and pulled the break away pin, the brakes were quiet. Those were good suggestions.

This certainly points to the trailer wiring being the problem. Since the problem is all the brakes, it must be where either the power supply or the grounds come together. I would start with the connections in the pin box. It is not likely the cord or connection to the truck since the break-away apply doesn’t work.

Rob

[StephenO]

Dave27 I would assume that if the brakes were working until you touched the wires around the axle, it sounds like those connections or wires need replacing.

Not sure if it helps, but with my TV, once it detects that the trailer has "disconnected" (I put it in quotes since nothing has been physically disconnected) nothing will work until I reseat the trailer plug. Super annoying when I was getting the trailer disconnected issue too.

[ncitro]

Dave27 If none of them are working (when it's failing) then the problem probably isn't in the backing plate. If you follow the wire forward from the wheels you should see splice connections where they tap off for the individual wheels. I would start with these splices.

[Cate&Rob]

Dave27 If none of them are working (when it's failing) then the problem probably isn't in the backing plate. If you follow the wire forward from the wheels you should see splice connections where they tap off for the individual wheels. I would start with these splices.

Dave27
I would agree with Neil's analysis. The first splice (that will affect all four brakes) is at the left front wheel. On the feed side from the pinbox, check the colored wire for +12V when brakes are applied. Check the white (or maybe black) wire for continuity to ground.

BTW, the non-functioning break-away apply could be a a separate problem. These switches fail open if the pin is not pulled and the contacts lubricated on a regular basis.

Rob

[phansen]

Mine quit working last year on my 07 Silverado and it was only the brakes. Little did I know, but $150.00 later, the dealer replaced the brake relay on the truck. It's located above the axle on the drivers side. Totally exposed and it had corroded enough it quit..

[Cate&Rob]

phansen
Hi Pat,
Good to have you join the discussion!

It would be worth checking for voltage at the 7 pin connector when the the truck brake controller is applied. Pin 1 to pin 2 (opposite the notch).

Rob

[Yoda]

There is one other place to look if your wires are good back at the axle. When I had my belly open I noticed a major wire bundle coming through several frame members from the left back corner of the front bay. Its below the buss bar that the wire bundel enters the frame. You need to undo the coroplast in the corner. GD did not uses grommets on these openings. You could have a chafed wire there.

BTW if you do have that corner open it would make it easier to pull a new break wire. The tough section is from the pin box to there.

[rsinkov]

On my last trailer I had a intermittent brake failure where they wouldn't work. The brake controller was replaced , but it didn't fix the trouble. The problem found was that one brake wire was laying against the leaf spring and had rubbed through the insulation grounding the brake circuit. A piece of electric tape fixed the problem and I placed all wires in split plastic wire covers to prevent any future issues.

[Dave27]

It would be worth checking for voltage at the 7 pin connector when the the truck brake controller is applied. Pin 1 to pin 2 (opposite the notch).

Rob

[/QUOTE]

Cate&Rob I checked the voltage at the 7 pin connector. There is no voltage between the brake and ground connections when the controller is applied. There is over 14v between the charging pin and ground, whether or not the brake is applied. I also checked with the brake pedal is used, and no voltage. There is voltage for the brake lights and tail lights.

So the problem could be on the truck side. What kind of business should I look for to check this out? Would someone that installs 7 pin receivers and hitches know about this? Or do I need a truck dealer?

Everyone is giving me good suggestions, and things to look for. I tried checking out where the wires are split to go to the first axle. It is hard to get in there, I can't see or feel where the split occurs by loosening up the corroplast in that area.

thank you all for your help.
Dave

[Guest]

Your 7 way plug is replaceable on the truck. Disconnect this from the truck bumper and disconnect from the vehicle harness. You can then check the connections at the harness where it pugs into the 7 way plug just behind the bumper.

Check for diagnostic codes for the brake controller.

This can all be done at the dealer and while they should find the problem quickly, their hourly rate can be high.

One thing that is important on GM trucks. You will want to use only a Pollak plug.

Pollak Replacement 7-Pole, RV-Style Trailer Connector Socket - Vehicle End Pollak Wiring PK11893

Jim