Bendix compressor governor test

SMMTX · 09-07-2020, 08:02 PM

My compressor is running, but zero air pressure. I have read on another forum, if you disconnect the governor and start the bus, if the compressor starts charging that was the problem. Replace it. If not, move on to the next possible problem. Problem is disconnect was not defined. I would think that just means disconnect both hoses. Does anyone agree or disagree with this test. Don't want to do anything damaging lol. There is no hissing btw.

Booyah45828 · 09-07-2020, 08:17 PM

How do you know your compressor is running?

Did you disconnect the line from the compressor and see if it's pushing air?

That's the first step when you cannot produce air pressure.

Then you can move onto disabling the governor. However, the only time I've ever seen a governor not allow a compressor to pump is when it was filled with water and frozen solid.

For the governor to unload the compressor and stop it from pumping, it uses air pressure. If the system doesn't have air pressure, slim chance the governor is applying air pressure to the compressor.

SMMTX · 09-07-2020, 08:42 PM

I believe is it running because I have touched it and hear the characteristic tapping. I always had some separation in the two pressures, but did not read about that in time to see how much. I believe between 5 and 10 at most, not sure which one the most. Right now the red line creeps up to 2 or 2.5. I can release that and see it did build up a tiny bit. No air escaping that I can hear, crawling rear to front. Push pull knob seems to be frozen in our position, but maybe because I pushed it several times after this started. Feel like it is some lock out or ignition sequence error, if not the governor. Also read should always have one on hand, so if not the problem I will have it on hand.

When you said disconnect from compressor, isn't that just the other end of the hose I am suggesting removing. If I remove it at the governor while the engine is running I could check for air there. If there is pressure, turn it off, take off the other line to dryer and start to see if the compressor charges the tanks that way. This is what the truck forum seemed to suggest. Would this work. I don't have inline pressure gauges.

Booyah45828 · 09-07-2020, 09:06 PM

Push pull knob, or spring brake knob, won't release until you have a minimum amount of air pressure. That's a safety feature.

I'm talking about the line from the compressor outlet to the air dryer. Pull it off either at the compressor or the dryer, and see if you have air movement.

Your compressor will have at minimum an air inlet, air discharge, and an unloader port. Some compressors are liquid cooled and will have 2 coolant lines entering them, some also have lube oil supplied by the engine and can possibly have a return as well.

I'm wanting you to remove the air discharge line. It should be half inch or so in diameter and will likely be copper or braided stainless due to the heat and vibration present. It will also be going towards the air dryer or, in case of no air dryer, the wet tank.

SMMTX · 09-07-2020, 09:14 PM

Okay thanks, I can do that I know the line you mean. I will go back to Bendix and make sure. I do have a dryer.
So if no air, is the compressor the only possible problem? Like replace it? I do also know that when I had it tuned up upon pick up, it blew water 20 ft or so when he blew the tanks. Very loud when it was operating, now quieter but same noise.
Hope I don't have to replace it that sounds expensive.

Booyah45828 · 09-08-2020, 07:40 AM

With the engine running, if you have no air coming out of the discharge port, the next step is to remove the line or governor from the unloader port. Start the engine again, and if you still have no air pumping, then you know the compressor has failed, or it's inlet is blocked by something.

SMMTX · 09-08-2020, 08:01 AM

Okay, yes read I need to inspect the lines all the way for kinks.
Very helpful answers, thank you.
Now I just need to go find those hoses... Newbie, so learning.
Cheers.

Oliveguam · 09-10-2020, 05:50 PM

For what its worth after when I fired up the tc2000 up for the first time (had sat a few years) it was hardly audible but leaking off the bottom of air dryer just as fast as it could pump a couple taps with a strewdriver handle and purge valve sealed and it pumped up and worked well ever since. Alos of not make sure to inspect intake for compressor, I have seen mud dobber nests clog up intake. Compressor cant compress what it cant suck.

SMMTX · 09-11-2020, 07:30 PM

I will check that out thanks. My inspection sticker ran out in July so probably in use at least the first of last year. I have lots of wasps here, so they could have blocked it after bringing it here. I am waiting for the rain to stop before I get under there again. REALLY scary for me when it is running. I know the belts are not nearby, but still freaks me out. I will get more used to it I guess with time.
One of the problems I had to solve was that I couldn't find a simple diagram of my components. The knowledge base expected when you read a service manual and open a hood is that you at least know where the compressor is. Had to find that. Next step at least after checking discharge is following lines. I can do that lol.

jofred99 · 09-07-2021, 04:22 PM

Quote:

Originally Posted by Oliveguam

For what its worth after when I fired up the tc2000 up for the first time (had sat a few years) it was hardly audible but leaking off the bottom of air dryer just as fast as it could pump a couple taps with a strewdriver handle and purge valve sealed and it pumped up and worked well ever since. Alos of not make sure to inspect intake for compressor, I have seen mud dobber nests clog up intake. Compressor cant compress what it cant suck.

Big Thanks for sharing about the purge valve! I have a short TC2000 that was having this exact problem. A couple of taps on the valve and pressure starts building.

Good lesson for anyone with a bus.

You may also like: