The brakes quit working on my car hauler trailer. Found out I am getting no juice for brakes at the factory Trailer connection per a wiring diagram. All lights work fine on the trailer.


Is there a fuse for trailer brakes ?

yes, but it is before your controller.

Thanks,


I installed the used brake controller a few years ago and I do not remember anything about the fuses. Would the blown fuse be under the dash ? http://www.dieselplace.com/forum/smileys/Confused.gif.

Mine is in the in-cab box, just inside the door jamb. Any lights on the controller?

There is a red light on the controller that should light up when activated. I have not noticed whether it still lights up. hm ........That might tell me something. I have a test light etc. so I might be able to find the problem.


I find it helps to have some one point me in the right direction though, as I have fumbled on problems like this for hours.

I have been assuming you are tapped into the power block under the dash. Correct?

I'm pretty sure I am tapped in under the dash at the cab fuse box.


I know I used the brake controller cable and a fuse that came with my 2002 HD duramax.

http://www.dieselplace.com/forum/smileys/Ermm.gif...Doesn't his '02 have a 30 Amp fuse in the UHFP for the brake controller like my '04 does?


Stud #1 is 40 Amp for trailer power/battery charging and stud #2 is 30 Amp for brake controller power on mine.

http://www.dieselplace.com/forum/smileys/Ermm.gif...Doesn't his '02 have a 30 Amp fuse in the UHFP for the brake controller like my '04 does?


Stud #1 is 40 Amp for trailer power/battery charging and stud #2 is 30 Amp for brake controller power on mine.

You are right. The trailer turn signal and stop light fuses are in the cab. My fault.

I did not get to look yesterday but When I get time today I will go look for the fuses you gentlemen are refering and let all know the results.


Thanks,


gmccall

Okay, the Stud #2 30 amp fuse in the under hood fuse block looks good and the red light on the brake controller comes on when I push the brake, but I still get no power to the trailer brake prong at the plug connection. Maybe the controller is broke.


Is there another fuse to look for in this case ? http://www.dieselplace.com/forum/smileys/Confused.gif

The lite is the truck stop lamps maybe, manually apply trailer brakes and see if lite comes on.


What kind of controller, my Hayes controller has a lever to set the penduloum(sp?) if this is not set correct then no brakes.


It could be the design of controller has to have reduction in forward motion to apply brakes so the brake pedal sitting still won't help,try the manual apply lever then test the trailer plug.


test the wires going into the controller first, then if u do have power in and no out replace controller.

Not that I am aware of. Time to start tracing wires. Start at the brake controller and make sure it is putting out.

Thanks for the suggestions, I will find it.

Okay, here is what I have found out.


The brake controller is working and will apply Juice to the dark blue wire on the trailer wiring harness that plugs into the fuse box under the dash. The diagram says the dark blue wire is for trailer brakes.


So I am getting juice there. From there I see no fuse listed on any of the fuse blocks in the truck manual that might apply. This truck has so many fuses. http://www.dieselplace.com/forum/smileys/Confused.gif


Any suggestions ?

There are no fuses between there and the back of the truck that I am aware of.

If it were me, I would now start at the Trailer socket and work my way forward. Jumper from one of the turn signals and the brake terminal. Turn on the turn signal, this will give you a nice pulsing signal to trace. Then, using one of the testers that you can poke through the insulation, look for voltage in the blue (brake) wire starting at the trailer socket. It very well could be in the plug/socket itself.

Hope this helps..

Good idea Fingers.


Thanks

Fingers is right about the socket itself, anything from corrosion to one of the wires having a problem back inside the socket.


One quick thought, a lot of these problems can be traced to ground circuit glitches.


Make sure you've got a good ground through that socket as well as power. Since your lights work, it may not be a problem, or they could be grounding through the trailer ball which is good enough for lights, but won't handle the current for the brake application.

I have to clean the sockets occasionally,so I will check for corrosion.


However When I activate the brakes and ground my test light and touch the prong for brakes in the socket (top right prong per a wiring diagram ) I get no juice at that prong. I do activate juice for stop lights. Makes me believe my problem is a break in the hot wire for the brakes somewhere. hm.......

Well, find the bugger yet?

Well, find the bugger yet?



No sir I have not. http://www.dieselplace.com/forum/smileys/Embarrased.gif Sometimes I think I'm worthless. I was too busy over the weekend, but I will find it. I did find time to dyno, but thats another post.


I will be pulling again over Labor day weekend so I need to find the problem. I plan to start at the rear trailer connector with the probe tester to see if I am getting power there. I am hoping it is nothing more than corrosion. I do think this story would benifit all so I sure will post results.

Check and see if your third brake light is working, my brakes went out checked every thing was the third brake light.Also might be magnets on trialer if it is replace the hubs.

Trailer brakes are working. http://www.dieselplace.com/forum/smileys/Big Smile.gif


I did not do anything I know of that would fix the brakes. They started working when I pulled this past weekend. For the record I replaced a tail light assembly but I don't see how that would fix the problem.


Also for the record when I apply the brakes in the driveway ,truck in park, the trailer connector prong that works the brakes (top right per wiring diagram) does not have any voltage. Three prongs do have voltage, but I have not traced those.


Third brake light was working BTW.Edited by: gmccall

Looking into the socket with the key on the top. The top right should be the AUX power. Lower right is the Brake power and will give you a low voltage connection with the brakes applied. Ground is top left.

Yikes ! I have been looking for the wrong prong to be hot. http://www.dieselplace.com/forum/smileys/Cry.gif


Thanks Fingers for that info. The lower right has been hot, since I have been testing. I will reread and correct if necessary my wiring diagram.


One thing comes to mind is the ground must have been corroded either in the socket or at the trailer ball, when the brakes did not work.

With the brakes on, you should have power to the middle left and right as well as a lower voltage signal to the lower right. You should also have power to the upper right if the aux power is hooked up.

Trailer brakes are working. http://www.dieselplace.com/forum/smileys/Big Smile.gif


I did not do anything I know of that would fix the brakes. They started working when I pulled this past weekend. For the record I replaced a tail light assembly but I don't see how that would fix the problem.


Also for the record when I apply the brakes in the driveway ,truck in park, the trailer connector prong that works the brakes (top right per wiring diagram) does not have any voltage. Three prongs do have voltage, but I have not traced those.


Third brake light was working BTW.





Is it possible that the tail light assembly had some sort of ground in it that was sucking all the power away from the brakes?


Dennis

With the brakes on, you should have power to the middle left and right as well as a lower voltage signal to the lower right. You should also have power to the upper right if the aux power is hooked up.


I have power exactly as you describe here. I do not have the fuse installed for aux. power. http://www.dieselplace.com/forum/smileys/Big Smile.gif

Trailer brakes are working. http://www.dieselplace.com/forum/smileys/Big Smile.gif


I did not do anything I know of that would fix the brakes. They started working when I pulled this past weekend. For the record I replaced a tail light assembly but I don't see how that would fix the problem.


Also for the record when I apply the brakes in the driveway ,truck in park, the trailer connector prong that works the brakes (top right per wiring diagram) does not have any voltage. Three prongs do have voltage, but I have not traced those.


Third brake light was working BTW.





Is it possible that the tail light assembly had some sort of ground in it that was sucking all the power away from the brakes?


Dennis





Dennis,


I would not think so. Brakes should work even if you have a busted tail light.

I was thinking more along the lines of a short somewhere internal to the assembly, causing excessive current draw through the tail light assembly, not allowing sufficient power to the brakes. . . If you still have the old one, you could measure the resistance between the power and ground and see if there is unusually low resistance.


DennisEdited by: baimpala

I threw the busted tail light away, but the tail light is all that I replaced so you may have a point.


Although from appearances, both lenses were cracked is all that was wrong with the old light. I probably could have replaced both lense to repair the unit, but the tail light was dirty inside and I replaced it with a new one. Their cheap.