Air coming out of air governor exhaust and not building pressure

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Air coming out of air governor exhaust and not building pressure

June 24, 2024, 01:21:33 pm

We have been having an intermittent—yet more frequent problem with not building air pressure. It will build up only to 30 psi. There is air coming out of the air governor exhaust port. We just replaced the air governor, but nothing changed. Still blowing air out of the exhaust and not building pressure. What is the next step?

Re: Air coming out of air governor exhaust and not building pressure

Reply #1 – June 24, 2024, 01:34:11 pm

Are you sure you matched the fittings to the right ports? Always take a picture before doing air or electrical wires and air line removal.

Re: Air coming out of air governor exhaust and not building pressure

Reply #2 – June 24, 2024, 02:24:59 pm

Quote from: snappytaylor – June 24, 2024, 01:21:33 pm

We just replaced the air governor... Still blowing air out of the exhaust and not building pressure. What is the next step?

It would be helpful to know the year and model of your coach. You can add this info to your signature on your profile page.

See if the D-2 instruction sheet offers any clues:

The selected media item is not currently available.

Re: Air coming out of air governor exhaust and not building pressure

Reply #3 – June 24, 2024, 02:41:54 pm

We have a 2003 GV 320. I added this to our info

Re: Air coming out of air governor exhaust and not building pressure

Reply #4 – June 24, 2024, 02:49:33 pm

It could be that the new governor is bad. I have had that happen to me several times over the years. Just because it says new or rebuilt don't mean that it will work.

Mike

Re: Air coming out of air governor exhaust and not building pressure

Reply #5 – June 24, 2024, 03:24:48 pm

Yes, we are considering the possibility of bad new part and are going to get another one. Hopefully that is it. Would still appreciate other trouble shooting tips in case that is not the case.

Re: Air coming out of air governor exhaust and not building pressure

Reply #6 – June 24, 2024, 03:53:36 pm

Quote from: craneman – June 24, 2024, 01:34:11 pm

Are you sure you matched the fittings to the right ports? Always take a picture before doing air or electrical wires and air line removal.

This was my first guess...easy to do when it can be configured multiple ways. That's the reason the governor comes with the port plugs included but not installed

Re: Air coming out of air governor exhaust and not building pressure

Reply #7 – June 24, 2024, 04:37:42 pm

Can you take it back to where you bought it and tell them it's defective? If it was shipped that a different story.NAPA auto carries them.

Re: Air coming out of air governor exhaust and not building pressure

Reply #8 – June 24, 2024, 05:16:49 pm

If your air dryer has an isolation valve it could be stuck not letting air pass. Not likely but possible.

Mike

Re: Air coming out of air governor exhaust and not building pressure

Reply #9 – June 24, 2024, 06:34:19 pm

How about a picture?. At least we might be able to see if anything is wrong. If you are not 100% sure you put the hoses back in the same locations, you could follow the hoses and let us know which one goes where.

Re: Air coming out of air governor exhaust and not building pressure

Reply #10 – June 26, 2024, 06:12:26 pm

OK, so some new developments since our last post. Our tech support guy had us do a few tests and determined that we had an internal issue with our compressor. We were able to find a shop and are waiting on the part and for them to get us in. To get on the road, we capped off the storage tank return line to the governor and were able to get pressure to build to 125psi. We cracked drain valves to avoid over pressure in the system. It was somewhat of a challenge because it was hard to maintain constant pressure at different RPMs. We had to stop several times and adjust the valves to keep going. We are confused because if we are able to build pressure in this manner, it seems like the compressor is working. Any thoughts? We are tempted to try another governor, but as the problem has been somewhat intermittent up until now, we are afraid that if it works, the problem may reappear down the road.

Re: Air coming out of air governor exhaust and not building pressure

Reply #11 – June 26, 2024, 06:17:16 pm

Sounds like the unloader valve is stuck open. You could spray Corrosion X into the intake of the compressor and see if it frees it up.

Re: Air coming out of air governor exhaust and not building pressure

Reply #12 – June 27, 2024, 12:20:41 am

Yes. Our tech guy thought unloader valve too. We already tried to spray PB blaster into it. Didn't fix it.

Re: Air coming out of air governor exhaust and not building pressure

Reply #13 – June 27, 2024, 08:34:43 am

Quote from: snappytaylor – June 26, 2024, 06:12:26 pm

To get on the road, we capped off the storage tank return line to the governor and were able to get pressure to build to 125psi. We cracked drain valves to avoid over pressure in the system. It was somewhat of a challenge because it was hard to maintain constant pressure at different RPMs. We had to stop several times and adjust the valves to keep going. We are confused because if we are able to build pressure in this manner, it seems like the compressor is working. Any thoughts?

I agree with your logical conclusion. If the air compressor supplies pressure to the wet tank then the air compressor is working.

Since the air compressor is sending compressed air to the wet tank, this would seem to rule out a stuck unloader valve.

If the compressor unloader valve is functioning, then your problem must lie elsewhere.

When you "cap off the storage tank return line to the governor" this effectively disables the D-2. Without a pressure supply line from the wet tank, it does nothing. With the D-2 disabled, your air compressor works. With the D-2 enabled, your air compressor doesn't cut in, and you get air continuously blowing out of the D-2 exhaust port.

To me, this still seems to point at a problem involving the D-2. Three possibilities:
1. It is installed incorrectly (as postulated early in this thread)
2. It is installed correctly but for some reason it is sending a continuous "unload" signal to the compressor.
3. A malfunction in the air dryer is sending pressure backwards through the control line to the D-2 where it then blows out the exhaust port.

Is your D-2 bolted directly to the air compressor, or mounted remotely on the frame?

You could try reconnecting the D-2 supply line (from wet tank) and disconnecting the unloader line that goes from the D-2 to the air dryer. Cap it off. This will disable the air dryer. Start the engine and see what happens?

Since this is simply my armchair deduction, don't assume it is correct. However, if it was me, I would be looking at whatever controls the operation of air compressor, rather than the compressor itself.

Good luck!

Re: Air coming out of air governor exhaust and not building pressure

Reply #14 – June 27, 2024, 11:42:14 am

This got me looking into how this system works. The D2 governor has 1 exhaust port, 3 reservoir ports and 3 unloader ports. I have been wrong before but in looking at the drawings. The governor gets air pressure in on a reservoir port. When the set pressure has been reached, air pressure is applied to the 3 unloader ports. Once the pressure on the reservoir port is at the cut in pressure the governor then releases the air pressure on the unloader ports by releasing to the exhaust port. The only way that air should be coming out of the exhaust port is when the governor has released the air pressure from the unloader ports.

So for air out of the exhaust port of the D2 governor is during the cut out process, bad D2, or possibly the hoses are connect wrong.

Here is a great video of how the system works.

https://www.youtube.com/watch?v=bmgSwSeLk_o

Re: Air coming out of air governor exhaust and not building pressure

Reply #15 – June 27, 2024, 12:17:52 pm

Thanks Turbo,

Informative video which I had to watch several times to really follow. My question after watching is where should I look to find my safety relief valve?

Richard

Re: Air coming out of air governor exhaust and not building pressure

Reply #16 – June 27, 2024, 12:21:15 pm

Quote from: Jan & Richard – June 27, 2024, 12:17:52 pm

My question after watching is where should I look to find my safety relief valve?

The safety valve mentioned in the video will, on most Foretravel models, be mounted on your wet tank (first tank after the drier). It is normally sized on our coaches to open at 150 psi.

Re: Air coming out of air governor exhaust and not building pressure

Reply #17 – June 27, 2024, 12:31:24 pm

We are in a shop now. Fingers crossed.

Re: Air coming out of air governor exhaust and not building pressure

Reply #18 – June 27, 2024, 02:13:44 pm

Please post the solution.

Re: Air coming out of air governor exhaust and not building pressure

Reply #19 – June 27, 2024, 02:32:58 pm

For others that want to troubleshoot on their own, here are some thinks to check.

Trace out lines and make sure correct line is going to correct port.
Verify ports that are not used are blocked off, Exhaust port should be left open. It is the one on the bottom, closest to the adjuster. Picture of ports here https://trucktrailerspares.com.au/wp-content/uploads/2024/02/AB831320D220Governor20Valve20dia-600x600-1.jpg

Verify all lines are not crimped, plugged, or leaking.
If above is correct, buy a new D2, they are cheap and most times fairly easy to install.

The following I don't think will help the original poster since his complaint was air coming out of exhaust port.

Verify unloader valve on compressor is working. Remember it takes air pressure to cause the unloader to engage so if no air pressure going to the unloader, then it will not start bypassing. To verify it will bypass, Put pressure to unloader and verify compressor bypasses.

Verify you have pressure from the wet tank.

The output of the D2 goes to both the unloader of the compressor and the unloader of the air dryer. If the seal is out on the air dryer there is a good chance you will not have enough air pressure to open up the unloader on the air compressor so the compressor would keep building pressure.

Re: Air coming out of air governor exhaust and not building pressure

Reply #20 – June 27, 2024, 03:47:21 pm

Not to fix your problem, but it reminded me of a simple mod we made to keep water (like from washing engine, etc.) from entering D2 at its open exhaust port. With an elbow in the exhaust port, we ran a couple feet of hose open at end, downward.

Re: Air coming out of air governor exhaust and not building pressure

Reply #21 – June 27, 2024, 05:12:14 pm

Quote from: Barry & Cindy – June 27, 2024, 03:47:21 pm

Not to fix your problem, but it reminded me of a simple mod we made to keep water (like from washing engine, etc.) from entering D2 at its open exhaust port. With an elbow in the exhaust port, we ran a couple feet of hose open at end, downward.

On page 4 of the Bendix Service Data document linked in Reply #2, it says the D-2 (when remotely mounted) should be positioned with the exhaust port pointing down. I assume for the same reason - to help prevent water from entering the port. However, on my coach and several others I have seen, Foretravel mounted the D-2 in a vertical position. Guess they didn't read the instructions. Pertinent paragraph copied below. I added the color for emphasis:

INSTALLATION
1. If the governor is compressor-mounted, clean
the mounting pad on both the compressor and
governor. Clean the connecting line, or lines. Be
certain the unloading port is clear and clean. If
the governor is mounted remotely, it should be
positioned so that its exhaust port points down. It
should be mounted higher than the compressor so
that its connecting lines will drain away from the
governor.

Re: Air coming out of air governor exhaust and not building pressure

Reply #22 – June 27, 2024, 09:05:38 pm

Been 9 hours since was in the shop working on the problem. I hope they figured out what the problem was

Re: Air coming out of air governor exhaust and not building pressure

Reply #23 – June 29, 2024, 01:33:32 pm

We had the air compressor replaced in the shop. We drove about 2 hours. Everything was working fine. Sat for 2 days at campsite. Just restarted engine. Pressure sitting at 30psi and air blowing out governor exhaust at idle. When we put it in travel mode, it started building pressure and air exhaust out of governor stopped. Problem not fixed. Maybe just wasted $3,000. So, now ruled out compressor and governor. Must be air dryer? Now in Canada. Looking for parts. Air dryer is Haldex N4250. Thank you all for your expertise. Any new thoughts? Problem is still intermittent. We just restarted engine again after about 1/2 hour and all is working fine. Built up pressure at idle.

Re: Air coming out of air governor exhaust and not building pressure

Reply #24 – June 29, 2024, 02:03:26 pm

Quote from: snappytaylor – June 29, 2024, 01:33:32 pm

We had the air compressor replaced in the shop.
Problem not fixed.
Must be air dryer?
Air dryer is Haldex N4250.
Any new thoughts?

What compressor model did they install? Just want to be sure we are all on the same page.

There has been occasional confusion in the past (on this Forum) about properly matching air dryer to compressor.

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