Air compressor for rear airbags not coming on

[GinaParmesan]

Hi all, and happy Thankgiving! Normally the compressor kicks on right when you flip on the ignition, but not anymore. Also the pressure gauge says zero.

Any tips for where to start? Could it be a fuse or something? If there’s a few things I can check or wiggle before taking it into a shop, please let me know.

Not sure if this is related, but also the electric step isn’t retracting automatically when the ignition starts. That’s a recent change too. It works fine otherwise.

Grateful for your input. Hope you’re all having a lovely holiday!

[Waipio Rim]

When my compressor stopped working I broke out the digital multimeter with the plan of testing for power, starting at the compressor and working back through the pressure switch and relay to the battery. I didn’t get far, the compressor had power but would not run so I bought a replacement. You may get lucky and find that power goes through the 12v fuse panel and you have a blown fuse there.

[mtlagger]

Try tapping on the step motor with a plastic dead blow hammer. Sometimes they need some encouragement....and it wont hurt it.

[Kreimer]

Our compressor died along with our cruise control. It was a fuse.

[WayneG]

On the schematic for a 85 MH it shows 2 separate fuses for the step solenoid (B1) and the air compressor (C1)
They both end up in the same chassis location, so maybe someone put them both on one circuit?

[GinaParmesan]

Thanks all. Fuses in the 12V chassis panel were fine. I found a wire going to the compressor with a butt connector where the heat shrink was pretty much toasted through. Guessing it was installed with a loose connection, so I’ll redo it. Any other steps you’d recommend?

[GinaParmesan]

Originally Posted by WayneG

On the schematic for a 85 MH it shows 2 separate fuses for the step solenoid (B1) and the air compressor (C1)
They both end up in the same chassis location, so maybe someone put them both on one circuit?

Boy when I saw this I really got hopeful that one fuse would fix both problems. I’ll still keep looking for an in-line fuse to the steps. Far as I can tell my MH’s schematic doesn’t show a fuse for the step in the 12V box inside the glove box.

[Waipio Rim]

Originally Posted by GinaParmesan

Boy when I saw this I really got hopeful that one fuse would fix both problems. I’ll still keep looking for an in-line fuse to the steps. Far as I can tell my MH’s schematic doesn’t show a fuse for the step in the 12V box inside the glove box.

Don't give up hope just yet. On my 310, the panel in the glove box only has fuses for the Chevy chassis stuff - headlights, wipers, etc. The panel for the Airstream coach stuff is separate, on mine it is just above floor level in the kitchen area, near the converter gadget that charges the coach batteries and gives me 12v when plugged in to shore power.

[mayco]

I would start by turning your key to the on position and then go back by the compressor and check to see if you have 12v getting to that point. If you've got 12v there then the problem is with the compressor, the pressure switch, the relay, etc. if you don't have 12v at the compressor then you've got a fuse, connection, broken wire etc preventing power getting to the compressor. Get your test meter out and see what you have, then you can proceed from there and we can help.

If you've already found the wire feeding the compressor relay it should be easy to test it where it terminates there at the relay. The problem with trying to diagnose the problem without seeing your set up is that the systems changed over the years a bit so one size doesn't fit all. A couple pictures of your compressor controls could help us guide you through it if you need it.

The compressor should be tied to your chassis fuse block. Mine is under the dash on the firewall.

[GinaParmesan]

Photos below. Will dive in again tomorrow.

The compressor is mounted to the floor of the interior rear passenger-side storage compartment.

The overview pic is after I replaced the toasted connectors. I haven’t done the heat shrink yet.

[WayneG]

Assuming the compressor pressure switch is in good shape and is on the + wire, check to see where your compressor ground wire is going. It needs a good chassis ground.
The burning in that crimp connector could indicate various problems:
Corroded wires in the crimp, compressor drawing way to much current, compressor left running for way to long.
I moved my compressor indoors between the rear wheels and genereator box on the 270. It is out of the cold and wet and I added a circuit breaker, water separator, a unloader valve and a air chuck with a hose to do my tires.
Somebody needs to lock up my tools when I have too much spare time!

[mayco]

Good pics. I believe the yellow wire runs all the way up to your dash. Turn your key to the on position and test the yellow wire for 12v. Making sure your tester has a good clean ground. If it tests good then you knowvthe problem is in the compressor compartment. If it tests bad (no 12v) then the problem is in the wire or under the dash.

You can bypass your pressure switch and relay and apply 12v directly to the compressor feed wires to see if the compressor is functioning.

[GinaParmesan]

The power bypass worked...kind of. The compressor came on, but running it for 10 min didn’t fill the air bags at all. So I used my little compressor that came with our car in the manual air outlet. That got the psi up to about 75, enough lift to drive to a gas station.

My made-up story for that is the other component in the compressor closet that has yellow wire and a ground (square box, upper left corner of my pic) is somehow related to feeding air from the compressor to the bags, and thus not working because no power.

The 12v interior panel (kitchen) doesn’t use the glass tube fuses like @WayneG’s 2nd pic, only little black bricks with threaded terminals and connectors. Clean as a whistle in there. All tested positive for 12v power.

The fuses in the 12v panel in the glove box are all good too.

My hunch is that it’s another area. Manual says there’s an “Airstream automotive circuit breaker” but I can’t find the bloody thing anywhere. The manual says it’s “under the front access door” but I can’t see anything like it when I open the front grill. I see the isolator and a bunch of wires, but nothing that looks like the attached diagram. Under the doghouse cover there’s a thing that looks just like the solenoid in the diagram, but I thought that was the starter. It’s not under the step outside either.

Diagram shows that mystery breaker panel has a breaker for the step and DC power to the fridge. (Neither of those work.) Also on same panel a breaker for the air compressor. Suspicious!!

It’s not easy revealing how much I don’t know, but I’m determined to learn whatever I can. Thanks for advice and support, MUCH appreciated! And correct me if I’m wrong please! :

[GinaParmesan]

Originally Posted by mayco

The compressor should be tied to your chassis fuse block. Mine is under the dash on the firewall.

What is a firewall, and which area of the dash is it under?

[Waipio Rim]

The firewall is the vertical panel in front of your feet when you are in the driver’s and passenger’s seats. Kind of a misnomer for our coaches, as an engine fire is going to happen between the seats instead of in front of the firewall.

Does the yellow wire have power at any point when the ignition switch is on? If so, the power problem is not a fuse but with one of the other two pieces of the system (pressure switch or relay) that Mayco points to. I don’t know enough to tell you what in your picture is what, but the pressure switch will have two electrical connections and one air connection.

The compressor running but not lifting the coach sounds like either a bad compressor or a leak somewhere between the compressor and air tank.

Is the manual that you are using specific to your 290? It shows a connection for tag axle brakes, you don’t have those. You may have to follow wires from your steps and refrigerator to find where they are fused. My 310 has only two 12v fuse panels, the one in the glove box (maybe that’s the “front access panel”?) and the one in the kitchen.

[WayneG]

Some more photos from my 84
First, my compressor was originally powered off of the GM fuseblock. It is one of the yellow wires, and I think it goes to the accessories buss? I did move it to the house fuse panel because it was closer.

2nd, if yours is run off of a OEM circuit breaker, on my 84 all the heavy circuit breakers are on the front of the firewall on the drivers side. I only have 2 breakers in this shot, When I reworked the front I added more for other high power items.

[Smartstream]

Here is a picture of my 1987 345.



This is the vertical post behind the front access cover on the drivers side of the radiator. You can see the solenoid, the silver can at the top, and 4 circuit breakers, black bricks, mounted on the post. The solenoid is merely an electrical switch that is operated by an electromagnet when you turn on the ignition key. It provides 12 volts to the copper bar on the right side of the circuit breakers. The threaded post on the left side of each breaker provides 12 volts to the various systems in the coach.

The picture in the manual is kind of generic for all the motorhomes so you have to figure out what accessories you have and follow the circuits. The 345 is new to me so I haven't chased down many circuits but the book indicates the compressor is fed by one of these circuit breakers. My 1982 280 looks more like Wayne's 84 and the compressor was fed through a fuse in the Chevy fuse block like the one in your glove box.

To test the set up in my picture, with the key off you should have 12 volts at only one of the large threaded posts on the solenoid and none of the circuit breakers. When you turn the key on both large posts on the solenoid and both posts of all the circuit breakers should have 12 volts. I hope this helps.

By the way my 345 is not wired the way the book says it is supposed to be so don't try to figure where the wires are going in the picture. Whoever wired this must have been partying too much. The heater control on the dash works without the ignition key and the engine battery disconnected. It's hard to figure what somebody was thinking when they did this.

[GinaParmesan]

Originally Posted by Waipio Rim

Does the yellow wire have power at any point when the ignition switch is on? Not in the compressor cabinet, no. If so, the power problem is not a fuse but with one of the other two pieces of the system (pressure switch or relay) that Mayco points to. I don’t know enough to tell you what in your picture is what, but the pressure switch will have two electrical connections and one air connection. Cool, now I know that's the little cube in the upper left corner.

The compressor running but not lifting the coach sounds like either a bad compressor or a leak somewhere between the compressor and air tank.The compressor was uber loud so I'm not sure but there might have been a hissing sound.

Is the manual that you are using specific to your 290? Some pages are for different models (290/310/345) but that page was generic.It shows a connection for tag axle brakes, you don’t have those. You may have to follow wires from your steps and refrigerator to find where they are fused. My 310 has only two 12v fuse panels, the one in the glove box (maybe that’s the “front access panel”?) and the one in the kitchen.

Thanks @Waipio Rim!!

[Waipio Rim]

If there's a leak, you should be able to find it by squirting soapy water on the air connections until you see bubbles. I have found small leaks that way, but if you get no pressure at all the leak would have to be a major break.

Regarding power, i think it's time to look at the breakers under the hood that Mayco and Smartsream have pointed to. We have owned our 310 for a long time and I didn't know that those were there.

[GinaParmesan]

Originally Posted by WayneG

Some more photos from my 84
First, my compressor was originally powered off of the GM fuseblock. It is one of the yellow wires, and I think it goes to the accessories buss? I did move it to the house fuse panel because it was closer.

2nd, if yours is run off of a OEM circuit breaker, on my 84 all the heavy circuit breakers are on the front of the firewall on the drivers side. I only have 2 breakers in this shot, When I reworked the front I added more for other high power items.

Under the front access door the setup looks almost exactly like this pic. Just tested the 2 breakers and both have power.