Jeepjeepster
New Member
- Joined
- Mar 15, 2020
- Messages
- 6
Sorry to start two threads but I thought some others may run into these issues. If you've seen my other thread about airbag confusion then you know I'm helping a friend with a 2008 Chevy Avalanche. I read up enough to know that chevy decided to stop using the neat little plug that made installing a brake controller a snap. Finding the harness for the brake controller was no issue but thats where the easy part stopped. Im a Jeep guy and do not know much about GM products.
Friend told me that the lights were not working on his trailer and they always worked and still work when hooked up to other vehicles. Ok, grab the multimeter and start checking out the 7 pin plug. Ground appears good, no constant 12v power and nothing for the turn/stop/park lights. Go to check fuses and find a blown fuse for the rt turn, replace it. Figure out that he doesnt have power at all to the plug unless he has the key turned on and also, his brake lights on his truck only work with the key turned on. I guess this is a chevy thing according to the internet....
After I found the wiring taped up under the dash I grab the multimeter to double check everything. Ok, I've got a ground but no +12v power, and nothing from the brake pedal sensor. Do some readin and I learn that GM decided to not hook up the constant +12v for the brake controller or the hitch plug.. WHAT THE HECK? Find those tied up under the hood, go buy the nuts (M6x1 and M8x1.25 I think) and get that hooked up to the 2 studs made just for them. They are protected by a 30amp and 40 amp fuse. Now the brake controller turns on and I have everything working back at the 7 pin plug but still only with the key on...
So were buttoning things up and were still confused. I mount the brake controller and he noticed when I hit the manual brake button on the brake controller, the rear view mirror, some dash lights, and the air intake all try to turn on/open... Man, something strange is going on here. We back the truck up to the trailer just to see what we can figure out and the brake controller (hopkins proportional controller) doesnt recognize the trailer but if you hold down the manual button it locks up the brakes. Im thoroughly confused at this point. Thought maybe it was a bad new brake controller? Were talking and he tells me that his cruise control had quit working and he had read that a bad brake pedal sensor can cause that issue.
Wouldn't you know it, a new brake pedal sensor fixed all of those issues AND his battery was going bad in his truck. I'm not certain on this, but I think his truck was shutting off power since his battery was going bad. Thats why it kept shutting off power and things would start working with the key turned on. We had the doors open which was causing his battery volts to drop down, we ended up having to boost the truck to get it started. The brake controller was someway back feeding power from the bad brake pedal sensor which was causing the air intake to move around and the dash lights/rear view mirror to turn on. New battery and new brake pedal sensor and all is well. Cruise control even works now.
To add to the confusion, at some point someone had bent the 7pin plug bracket up so that when you tried to plug in the trailer wiring, it kept the plug from plugging all the way in... You couldnt tell what was happening unless you got down and really checked out the plug. So thats why his trailer lights weren't working... Even with the blown fuse some of his lights should have worked when the truck was running and the volts were good.
Friend told me that the lights were not working on his trailer and they always worked and still work when hooked up to other vehicles. Ok, grab the multimeter and start checking out the 7 pin plug. Ground appears good, no constant 12v power and nothing for the turn/stop/park lights. Go to check fuses and find a blown fuse for the rt turn, replace it. Figure out that he doesnt have power at all to the plug unless he has the key turned on and also, his brake lights on his truck only work with the key turned on. I guess this is a chevy thing according to the internet....
After I found the wiring taped up under the dash I grab the multimeter to double check everything. Ok, I've got a ground but no +12v power, and nothing from the brake pedal sensor. Do some readin and I learn that GM decided to not hook up the constant +12v for the brake controller or the hitch plug.. WHAT THE HECK? Find those tied up under the hood, go buy the nuts (M6x1 and M8x1.25 I think) and get that hooked up to the 2 studs made just for them. They are protected by a 30amp and 40 amp fuse. Now the brake controller turns on and I have everything working back at the 7 pin plug but still only with the key on...
So were buttoning things up and were still confused. I mount the brake controller and he noticed when I hit the manual brake button on the brake controller, the rear view mirror, some dash lights, and the air intake all try to turn on/open... Man, something strange is going on here. We back the truck up to the trailer just to see what we can figure out and the brake controller (hopkins proportional controller) doesnt recognize the trailer but if you hold down the manual button it locks up the brakes. Im thoroughly confused at this point. Thought maybe it was a bad new brake controller? Were talking and he tells me that his cruise control had quit working and he had read that a bad brake pedal sensor can cause that issue.
Wouldn't you know it, a new brake pedal sensor fixed all of those issues AND his battery was going bad in his truck. I'm not certain on this, but I think his truck was shutting off power since his battery was going bad. Thats why it kept shutting off power and things would start working with the key turned on. We had the doors open which was causing his battery volts to drop down, we ended up having to boost the truck to get it started. The brake controller was someway back feeding power from the bad brake pedal sensor which was causing the air intake to move around and the dash lights/rear view mirror to turn on. New battery and new brake pedal sensor and all is well. Cruise control even works now.
To add to the confusion, at some point someone had bent the 7pin plug bracket up so that when you tried to plug in the trailer wiring, it kept the plug from plugging all the way in... You couldnt tell what was happening unless you got down and really checked out the plug. So thats why his trailer lights weren't working... Even with the blown fuse some of his lights should have worked when the truck was running and the volts were good.
