Humming brakes

[StreamRollin]

Haven't trailered the Airstream (1999 25'ft Safari) for about 18 months. When I connect the trailer to the truck, the brakes on the Airstream have a high-pitched hum. Inside, the truck, the controller is displaying NC for no connection. I did manage to drive 2 hours through the mountains, back home, I can feel the Airstream brakes applying and we didn't have any issues with squealing or smoke. All the running lights work just fine, so I am not sure if it's the 7-pin connector, or something else. Anyone run into this? I searched the thread but didn't find anything, so sorry if this is a duplicate. Jim

[HowieE]

What brake controller are you using. Manufactures harness to brake controller or hard wired? When you step on the brakes do you see a current reading on the controller? When on the brakes did you fee additional drag from the trailer? If the brakes are humming they are engaged.

[A W Warn]

Did you check the breakaway switch? Maybe the pin has been pulled.

[StreamRollin]

Did check the brake pin and that's not it. My display on the Prodigy brake controller would go back in forth from NC to some broken up numbers. If the pin was bad wouldn't the brakes lock. Thanks Jim

[nrgtrakr]

My brakes don't hum (or sing - sorry).
My brake controller sometimes has an unusual display.
My brakes worked even with the unusual display (to include when the controller thought it wasn't connected).
Breakaway switches are supposed to lock up the brakes. This can be checked with a wheel in the air and the breakaway broken away - the wheel should not rotate.
What if the hum is not the brakes?

[DanB]

So you intentionally drove 2 hours with brakes that were activated? Well, to be blunt, I suspect you now have bigger issues then a wiring problem.

I suggest you get your Airstream to a repair facility.

[A W Warn]

First thing I would do is remove the plug on the trailer umbilical cord to see if there is a minor short between either the (+) wire that charges the battery or the (+) wire on the running light circuit and the (+) wire that activates the brake.
Second I would pull out and push back in the pin on the breakaway switch a couple times to clear any corrosion on the switch.
I suspect if it is not that, the controller itself is the problem.
It's going to take some detective work.

add edit: don't for get to unhook the ground from the battery while working on the umbilical

[StreamRollin]

hey thanks everyone for the constructive troubleshooting tips. I have a way at work to test with another trailer to see if it's the controller in the vehicle, and a call in to my friendly rv repair shop, in case it's the airstream brake system.

The wheels turn just fine and when the brake pedal is depressed, the brakes apply, so no, I did not intenionally drive my Airstream on a busy downhill mountain roadway with any brakes activated or not functioning at all, that would be some kind of stupid. I have no way of knowing where this hum is coming from, but it surely seems electrical.

thanks again. Jim

[HowieE]

Can we assume you only hear the hum outside and near the wheels?

I ask this because another source of a hum could be the convertor. The cheap World Friendship convertors used on a lot of newer RV the plates in the transformers loosen up and start to hum. Your trailer may be too old for that issue but a thought. Not sure how that could effect the display on your brake controller.

[NavyCorpsman]

Did the hum start with application of the TV brake pedal, and does it continue with manual application of trailer braking only? A hum can be caused by oscillation of an intermittent magnet coil.

[StreamRollin]

Solved! After quite a bit of troubleshooting today, we discovered that the brake controller fuse in the truck had blown. The pigtail wasn't getting enough power. I guess the singing was a warning. I am so grateful that it was a $5 fix.

Thank you all for your input. I appreciate it. Jim

[HowieE]

Lets not close this issue yet. A fuse is an either/or system and can not give a warning as to it's intent.

If the fuse was blown and you had current flow to the brakes there is another problem.

My first suggestion would be determine why the fuse blew. It is hard to blow a 30 amp fuse without leaving some evidence of burning.

[ROBERT CROSS]

...... a burnt out fuse is a symptom, replacing it is not likely the fix, (unless it was defective from the start).

I've found the Fuse Buddy helpful in the diagnosis of the cause.

Bob

[StreamRollin]

Well guy's this is what I know on this issue. The positive output on my TV outlet showed very week on the meter reading. Which lead use ( service tech from our service dept at the Toro Co.) to believe that a fuse had blow on the electric brakes. Once replaced with new fuse and hooked up to a trailer in our yard every thing was working fine. Then when I got home I looked at the power cord from the camper saw no bare wires , all connections looked good , I cleaned the blades in the plug with some 60 grit sand paper to clean out some corrosion. Then I plug the camper into the TV and everything was working like it had some 18 months ago. Service tech thought that maybe it had blown when I had removed the plug or there was moisture when it was plugged back in when this problem first started. So stay tuned , on Aug,28th we will be hooking back up and heading to Utah . Will let you know how it goes. Thanks Jim