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garyb1st · 06-08-2022, 11:13 AM

The braking system on our motorhome stopped working. On a gas motorhome like ours, an air compressor is installed on the chassis. Then as far as I know, it works the same as on a diesel motorhome that has air brakes.

We had a problem several years ago and it turned out to be the compressor. The dealer installed another compressor and we've had no problems since.

When the first compressor failed it simply would not turn off. The only way to shut it off was to remove the in-line fuse. This time, the air compressor will not start. Hoping it was just a fuse issue again, I replaced it. Still, it would not turn on. The fuse that I replaced had continuity but it was quite dirty and there were spots on the fuse where there was no continuity.

The problem began after traveling I-70 east through Denver. It was raining and at elevation it was snowing. Quite a bit but not enough to stop traffic.

I mention that since we're SoCal based and don't see much rain and humidity. So wondering if moisture a problem.

The manual says that cleaning and draining the compressor after a few trips is necessary. I've never done that. I will do that to see if there's much water in the compressor. If not and I can't find a wiring issue, I'm not sure what to look for. Finding someone to look at it is almost impossible. The dealer that installed it is more than 2000 miles from us.

Another thing that may be part of the problem is the dash mounted light which illuminates when braking. That has stopped working. Don't know if it's just a failed bulb or if there's a connection.

Any suggestions will be much appreciated.

twinboat · 06-08-2022, 11:52 AM

Air compressors make water, air tanks can collect it, that's what you need to check and drain water from.

An electric air compressor will have a pressure sensing switch that shuts down the compressor when the system is at its set point and starts it when the PSI is low.

I have worked on all sorts of on and off road vehicles, even gas powered trucks with air brakes. They always had an engine driven compressor. I have never heard of a air brake system that depended on an electric compressor for service brakes.

rssnape · 06-08-2022, 12:00 PM

This brake is on your towed vehicle?

The compressor could have failed. if it ingested water it could lock it up. Electric Motors fail eventually. You will need to verify that the compressor is getting power, that the motor isn’t locked down or the compressor.
Start by draining the tank.

jacwjames · 06-08-2022, 12:26 PM

Here's a link to a compressor marketed for the 9060 Brakemaster
https://www.etrailer.com/Accessories...r/RM-8315.html

Is this what your compressor looks like?
In the picture you can see the pressure switch. There is also an installation guide which should have wiring schematic and possible list if there is a fuse.

johnhicks · 06-08-2022, 01:45 PM

You need to drain the tank daily.

Verify that you have voltage at the compressor and a good ground. If you have both it's either the pressure switch or motor.

As for the dash light, it's activated by the toad stoplight switch. Battery/power line to stoplight switch, stoplight switch closes, voltage goes up the line through the connector wire to the MH to the dash light. There's no fuse that I know of although of course there may be. Also check that toad ground to MH chassis is good.

For others, this is an electric air compressor providing proportional controlled air to the air cylinder of the toad brake system, which pushes the brake pedal. It works fairly well.

garyb1st · 06-08-2022, 01:47 PM

Twinboat, Opened the valve to drain the tank. No water drained out. All the wires seem to be fine.

garyb1st · 06-08-2022, 01:48 PM

rssnape, I'd like to determine if compressor getting power. Not sure how to do that. Can that be done with a simple volt meter? If I could determine whether or not the compressor failed, I could possibly replace it for less money than what an RV/truck repair facility would charge to check systems and then replace if necessary.

garyb1st · 06-08-2022, 01:48 PM

Jacwjames, Our compressor looks just like the one etrailer sells.

garyb1st · 06-08-2022, 01:54 PM

Quote:

Originally Posted by johnhicks

You need to drain the tank daily.

Verify that you have voltage at the compressor and a good ground. If you have both it's either the pressure switch or motor.

How do I check voltage at compressor?

Quote:

As for the dash light, it's activated by the toad stoplight switch. Battery/power line to stoplight switch, stoplight switch closes, voltage goes up the line through the connector wire to the MH to the dash light. There's no fuse that I know of although of course there may be. Also check that toad ground to MH chassis is good.

Again, not sure how to do that.

jacwjames · 06-08-2022, 01:56 PM

The compressor should have power coming to it via a wiring harness, it is probably key activated possibly even have to have the engine running. You should have 12 volts going to the compressor. If you have power going to it then you can start testing into the unit.

As twinboat suggested, there is a pressure switch that you should be able to test.

johnhicks · 06-09-2022, 09:13 AM

There's no telling how this thing is installed. Mine has a wire from the house battery (front passenger side) via inline fuse to a switch under left driver side dash, then out to the compressor.

Does your activation light connect via a separate wire from the toad or is it included in the six-wire or seven-wire connection?

garyb1st · 06-09-2022, 10:10 AM

Quote:

Originally Posted by johnhicks

There's no telling how this thing is installed. Mine has a wire from the house battery (front passenger side) via inline fuse to a switch under left driver side dash, then out to the compressor.

Does your activation light connect via a separate wire from the toad or is it included in the six-wire or seven-wire connection?

Pretty sure there is no wire from the house battery.

There is no unique wire from the toad. Everything works via the 6 way cord. I've done a continuity check on the cord and while one end is starting to come apart, there is continuity. In addition, all the lights work during the system check before heading out. Brake lights on the toad come on when I depress the motorhome brakes.

The compressor has always started every time we turn on the motorhome whether or not we're connected to the toad. So it's unlikely the toad wiring affects the compressor.

johnhicks · 06-09-2022, 04:24 PM

OK, at the top back of the compressor. I have an orange wire with an inline fuse and a ground wire, you should have something similar. When the compressor is supposed to be running, using a voltmeter check that orange (or red etc) wire and you should see 12 volts.

When disconnected, do your toad brake lights come on when you press the toad brake pedal and the engine is NOT running, either with the key off or the key in the unlock position?

garyb1st · 06-10-2022, 05:11 PM

John, my compressor has an in-line fuse like you describe. It had some corrosion but continuity. At least some times. I replaced it just in case and no change. I also removed and cleaned one of the ground wires. Not sure if there are more or it's the same you're referring to. Will check tomorrow to see if there is another ground wire.

I have a volt meter but not sure what to touch with the probes. I can see the red wire you mentioned but not sure if I need to disconnect before testing.

My skill set when it comes to automotive is pretty limited.

Do I need to have the engine running to do the test with the volt meter?

The toad brakes work whether connected or not.