Diesel Place banner

1 - 10 of 10 Posts

·
Registered
Joined
·
40 Posts
Discussion Starter #1
I’m not sure if this same issue has been discussed on here or not yet so bear with me. Went to rent a dump trailer the other day and found I had no trailer brakes...after hooking up to a second trailer figured out that the problem was my truck not the trailer. Started tearing into the wiring harness and followed bundle of wires until the fuel tank where its a bit hard to get to. Went back to the end and took voltage and here’s what I found...

right and left turn wires go from 0 to about 9 volts(seems normal)
park lamps were a solid 11 12 volts(good)
but the Electric brake or dark blue reads 4 volts with the just brake pedal engaged then read 10 volts with just the brake controller engaged
Am I missing something or is that sufficient for trailer brakes?
 

·
Registered
Joined
·
2,495 Posts
I believe your brake master cylinder has a sensor to determine how hard you are pressing on the brake pedal; the harder you press, the more voltage you should get. So how hard are you pressing and are you doing your testing with a trailer hooked up? And are ;you getting a TRAILER CONNECTED message on your DIC when you attach your trailer?
 

·
Registered
Joined
·
40 Posts
Discussion Starter #3
I believe your brake master cylinder has a sensor to determine how hard you are pressing on the brake pedal; the harder you press, the more voltage you should get. So how hard are you pressing and are you doing your testing with a trailer hooked up? And are ;you getting a TRAILER CONNECTED message on your DIC when you attach your trailer?
I had the wife in the cab pressing the brake while I took voltage, no change in voltage whether she pressed down all the way or lightly, and no trailer, truck is in garage
 

·
Registered
Joined
·
2,495 Posts
Well, I don't think you can accurately judge the controller one way or the other without a trailer attached, or maybe a 'fooler' having the same resistance as a trailer so the truck 'thinks' a trailer is attached. My brakes work perfectly and I can tell you that when driving down the street, no trailer attached, I will not see the blocks advance across the display,. If I attach my trailer, get the TRAILER CONNECTED message, then I see the blocks advance across the display when I step on the brake pedal with increasing pressure. That's when I know the trailer brakes are working properly.

You didn't say this, but you are talking about GM OE Integrated brake controls aren't you? Not an aftermarket controller??? If you are troubleshooting an aftermarket controller, forget everything I said. Maybe someone else knows what to expect from those - I don't.
 

·
Registered
Joined
·
40 Posts
Discussion Starter #5
Sorry I probably should have clarified, prior to 07.5 GM did not have factory integrated brake controllers(or at least I have yet to see one)
 

·
Registered
Joined
·
5,512 Posts
I'm having a similar issue only thing is I have not yet had a chance to test with another trailer. I have a Tekonsha Voyager controller. With everything hooked up all appears normal. I get the green light and if I use the manual lever or while driving it changes colors normally but no brakes.

If I connect a jump box to the trailer pins or pull the runaway pin the brakes lock up. If I connect a 50w 8 ohm resistor to the truck pins it gets warm and drops voltage. Seemed like things should work so when I got the two together still no work. Didn't have time to keep troubleshooting and yesterdays load wasn't bad.

I still have them together today so gonna go do some more testing but I'm not sure where to look next. The plugs look very clean. Connections on the truck plug were soldered including to the plug itself. Same with the trailer. Its a factory molded cable and a couple years ago I re did all the connections. They are soldered greased and heat shrinked.
 

·
Registered
Joined
·
5,512 Posts
I think my next test will be disconnect the brake wire at the controller under the dash and use a jumper wire there. If that doesn't work then I know its got to be a connection issue. If it does work then its somehow the controller even though my resistor test seems to indicate it was working. Actually I should just bypass the controller under the dash. That way I will be using the same power feed wire and fuse and everything but the controller.
 

·
Registered
Joined
·
5,512 Posts
I had some setbacks including a lot of rain and getting the truck and trailer stuck in mud iin my driveway so have not got back to the brake project yet. My skid steer also had electrical issues, I got really good at taking the hydraulic pump out since every issue seemed to be blocked by that darn thing. Then there is the new developments of the riots on top of the ongoing virus fun.
 

·
Administrator
Joined
·
15,674 Posts
I had some setbacks including a lot of rain and getting the truck and trailer stuck in mud iin my driveway so have not got back to the brake project yet. My skid steer also had electrical issues, I got really good at taking the hydraulic pump out since every issue seemed to be blocked by that darn thing. Then there is the new developments of the riots on top of the ongoing virus fun.
Stay safe over there!

(y)
 
1 - 10 of 10 Posts
Top