Intermittant Brakes

[dinoburb]

Hi Gang,

I have run into a problem that is new to me and that has been going on for some time, albiet without my knowledge until recently. I have upgraded my brake controller to a Prodigy and now I have discovered that I have intermittant brakes!

When I hook up the trailer the controller reports 'c' = connected. Pressing on the brake pedal I can adjust the amperage to the brakes per the instructions. The nice thing about the Prodigy is that it reports the amperage with each brake application, indicating the max amps applied during the stop or slow down event. However, it also indicates when there is a lost or no connection with an 'nc' in the indicator window. I see the 'nc' indication far too often. I can sit with the trailer hooked up and the truck off and the light will change from 'c' to 'nc' and back seemingly at will (who's Will?) (sorry can't help it!) While driving if the brakes are applied while the unit is in a state of connection it will stay connected and report the amperage being applied throughout the stop. However, the next application of the brakes the unit may be in a disconnected state and no power is being sent to the trailer's brakes.

I have rebuilt the trailer connector ( the one mounted on the trailer) by replacing the socket assy and trimming all wires back to bright copper. 25 year old wire ends, exposed to the atmosphere, tend to become brittle. That's been taken care of. The connector cord went through the same process: new connector plugs and trimmed wires. The truck socket has been replaced as well. All connections seem to be making good contact.

All lights on the trailer work all of the time (running, brake and turn). Battery recharges fully while driving.

If only one brake magnet wire were to break would the controller still 'see' the others and consider itself connected. The brake magnets are connected in parallel, I believe, so that should be the case.

Why do I have this phantom disconnect? It sure is good the 3/4 ton Suburban brakes are in good working order and designed to haul down such a large load. Now that I know what I'm looking for I can tell when the brakes are or are not working. Before, it was simply an uncomfortable feeling when the brakes were applied as some times the truck stopped much easier than other times.

Any help would be appreciated.

Take care,

[uwe]

Take your wheels and hubs off and physically check all the connections inside the brake assembly. i had 3 of them disconnected on my old axles once...imagine the improvement once all the wires were connected...
I had a Tekonsha Voyager brake controller back then, it did not monitor the connectivity.
Also, look for corrosion on all the pertinent splices. A lot of work, but worth every minute, for your safety.

[72 Excella500]

My 72 Excella did the same thing to me when I was pulling it through the Virginia mountains. What I found was I had a short to ground just in front of the forward axle under the belly skin. The wires had dropped down and chaffed on the skin. You are correct the brakes are wired in parallel. You are going to have to hunt it down. If you had one magnet broken it should not matter. You have a wire broken or bad connection between your plug and the axles. Depending on how handy you are with a multimeter you will find it. Another idea is to have someone step on the brakes and watch your controler while you start shaking down the wirs harness. Hope this helps.

[rluhr]

I have the exact same problem!

On my rig, the trailer is so lightweight that I haven't been able to determine if the brakes are in fact still operating when it is blinking "NC". Early on, I suspected that the brakes were working and that I just had a bad unit. It feels about the same when braking, and since it blinks "NC" so intermittently (1-10 seconds at a time) I usually don't have time to test carefully before the display changes back to "C".

A trip to the local dealer ended up with the theory that the 7-way connector cable was stiff with age, and pulling slightly out during travel. Solution recommended was a $48 extension cable. It seemed to work for a couple of days, but then the problem returned -- intermittently.

Now I'm leaning toward the "bad wiring" theory. We tried the easy stuff: having somebody shake and twist the connector wire while another person looked at the display -- no luck. The truck connector is new and all the contacts look perfect.

Next step is the multimeter. But that's just diagnosing the inevitable. I expect to drop the necessary belly skins and just rewire the whole darned thing. Unfortunately, that will have to wait until next spring because I don't have a garage to work in this winter.

I wonder how many people who have other brands of brake controllers have this issue and don't know it?

- RL

[Happycampers]

I had the same problem on my sob and the insulation had rubbed off the wire by the axel and would ground out and no brake then it would move off it from the shift of the trailer and back and forth. Had to rewire the whole brake system, that is when I found it. Marvin