12VDC Thompson Air Compressor Will Not Turn Off

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12VDC Thompson Air Compressor Will Not Turn Off

November 07, 2021, 12:35:20 pm

Yesterday I noticed subject pump was running more than usual. I went to check on it and about the time I opened the bay door the pump cycled off. I reached down to feel the pump housing to see if it was hot. Yikes!! It was hot. So I turned off power to the pump with a switch that acts like pulling the 5amp fuse. A couple minutes after I had switched off the pump power, I heard a click noise I assume came from the pump pressure switch. I then switched on the power to the pump and it came on. So the pump cycled off and then on in ~ 2 to 3 minutes. Since the pump was hot I again switched off the power. I waited several hours and then checked the pump housing to see if it was cool to the touch. It was, so I switched on the pump and it ran for ten minutes until I switched it off. When I switched on the pump the dash air gauges were reading 75 psi. After the pump ran for ten minutes the dash air gauges were still reading 75 psi. Went to bed and this morning I checked the dash air gauges - they were reading ~ 60 psi each. I switched on the air pump and ran it for 10 minutes. After running the air pump for 10 minutes the dash air gauges were still reading ~ 60 psi. There are no air leaks around the air pump and water bowls. I'm guessing the pump pressure switch has stopped working or maybe a check valve near the pump? Any ideas out there in Forum land?

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #1 – November 07, 2021, 12:54:24 pm

I'm not familiar with the air system on your 2003 model, so no specific help.

My first suggestion is to study the air system schematic for your coach. On some coach models (my '93 U280 for example) the aux air compressor is not designed (or plumbed) to add pressure to the main brake tanks. Running my aux pump has no effect on the dash pressure gauges. My aux pump feeds pressure directly to the HWH 6-pack manifolds, and is only intended to assist in the Auto Leveling process.

It is possible your coach is plumbed in a similar manner. Looking at the air system schematic will tell exactly where the output from the pump goes, and also where the pressure switches that control the pump might be located.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #2 – November 07, 2021, 02:42:57 pm

On my coach,
When I turn on the compressor it does bring up the pressure in the tanks that are shown on the dash.
Usually up to 100PSI

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #3 – November 07, 2021, 03:11:12 pm

Frank, looks like your brake air supply tank check valves are bad. HWH should be isolated from the brake system. FT Tech tells me this is a fairly common problem.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #4 – November 07, 2021, 03:21:36 pm

Quote from: SteveB – November 07, 2021, 03:11:12 pm

Frank, looks like your brake air supply tank check valves are bad. HWH should be isolated from the brake system. FT Tech tells me this is a fairly common problem.

On second thought my coach does have a switch on the driver console marked "Air Tank" that activates a solenoid valve that directs air from the HWH air pump to the wet tank which feeds the brake air tanks. If this switch is turned on and/ or the solenoid valve is stuck open I guess this would have the effect you are seeing. Just something else to consider.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #5 – November 07, 2021, 04:28:14 pm

Have you checked for any air leaks at your slide bladders? Or air lines going to the bladders.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #6 – November 07, 2021, 04:32:27 pm

It could be a leak in a bladder. Also could be the valve on the bottom of the bowl that dispenses moisture when the compressor shuts off.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #7 – November 07, 2021, 06:14:19 pm

Thanks for the suggestions. 12VDC pump air flows thru to wet tank and from there to brake tanks (see attach). There is a solenoid controlled by the dash key that allows air to flow to the wet tank. Dumped all the air in the wet tank and turned on the dash key and little pump with the wet tank dump valve open to see if any air was flowing into the wet tank. Nothing! Closed dump tank valve and turned on the little pump and started inspecting slide bladders. Living room slide bladder seemed ok. Then checked the closet slide and I could hear an air leak that was easy to locate. Bummer.

Was just at MOT a couple weeks ago for $8 coach bucks worth of service. Been nice if this problem had presented itself then. Now we are in El Paso headed west to SoCal for the Christmas holidays. Any suggestion on where we can get this repaired between El Paso and SoCol or should we head back east to Nac?

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #8 – November 07, 2021, 06:21:48 pm

One more follow question: Will losing the air in the closet slide bladder affect the living room slide bladder?

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #9 – November 07, 2021, 07:14:41 pm

You can turn off the air to the bedroom slide and still use the front sly

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #10 – November 07, 2021, 07:51:54 pm

I think your best bet is to head to Moscow, Iowa to the HWH factory, if it's not too inconvenient. Temecula Valley RV service in Temecula, Ca did ours but they want your coach for awhile now. When I did it I made an appointment to bring it in the day they would start work on it and picked it up the next day. I don't know what the lead time is at MOT or FOT . Ask MOT if they had check your bladders for any leaks!

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #11 – November 08, 2021, 09:15:36 am

What's the procedure for by passing the bedroom slide air so we can keep the front slide bladder operational?

We had discussed traveling to Indiana to have the absorbtion unit on our Dometic frig replaced with a 12VDC compressor. Maybe we could swing by Moscow IA (HWH) on the way. Our plans for the holidays didn't include a side trip to the mid-west in early winter.

It may be our only option. I had heard at MOT a couple weeks ago that bladders were in short supply. May have to park the rig somewhere in a dry climate until the supply chain is better.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #12 – November 08, 2021, 09:34:04 am

Quote from: rbark – November 07, 2021, 07:51:54 pm

I think your best bet is to head to Moscow, Iowa to the HWH factory, if it's not too inconvenient.

From Michelle back in May;

"FYI I did recently read on iRV2 that HWH has temporarily ceased Active Air installs due to loss of employees due to illness, primarily Covid-19 Active air install. I don't know if that might also impact response time specifically on Active Air support."

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #13 – November 08, 2021, 02:07:49 pm

David, there should be 1/4 turn air shut off valves on the manifolds for each slide out. Mine are located on the front wall of the electronics compartment. Just turn off the valve for the slide out that has the leaking bladder.
It may be wise to seal for the perimeter of the slide out with something like blue painters tape to keep out the weather and unwanted critters.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #14 – November 08, 2021, 03:26:17 pm

David, when I got my U320, I found that the check valve between the 12V pump and the wet tank was bad. It's right at the output of the compressor, line 57 if memory serves.

I added gauges to the output side of the HWH solenoids that go to the slide bladders, so I could see what pressure was in the bladders. The ball valves on the inlet side were well worn, and if you turned them, air leaked from the knob. I replaced them with ball valves from Lowes. This still let's me shut off air flow to either of my slide bladder solenoids as needed. By doing this, you can see if the bladder pressure stays up or drops off, indicating a leak somewhere.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #15 – November 09, 2021, 06:14:49 pm

Steve/Keith kudos for the help here. I think I have located the shut off valves (see picture). By turning off the leaking closet bladder I can keep air in the slide tank for the living room slide bladder. Yea!! Have an appointment with MOT next month to replace the defective bladder. In the mean time I have done some research on glues and patches for EDPM? rubber. Ordered the stuff from Amazon which will be here is a couple of days. After I do the voodoo application and let it cure for a couple days I'll back it up with Gorilla black tape which Ronnie at FOT suggested. Luckily the leak is on the side and there is about an inch of space to get at the seal. Staying in dry El Paso so should reduce the likelihood of a rain event. Dust is better that water. Have some blue painters tape handy just in case. PS - Talked with HWH today. One problem they are encountering is the materials they manufacture the bladders from is on back order. My guess the stuff comes from China and it's sitting in a ship in the LA harbor waiting to be unloaded. I'll hold the political comment for another time

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #16 – November 09, 2021, 07:37:12 pm

Not specific to your bladder issue but you might also want to check and see if this service bulletin was ever applied to your coach. Your build number is in range to be affected. Michelle had posted this at least one time before. I have the parts to apply the remedy to our coach but it hasn't made it to the top of the list yet.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #17 – November 09, 2021, 07:40:30 pm

Yup, those are the valves. Mine were original, as yours appear to be, and leaked badly when turned. That's why I replaced mine.

The round black thing in your picture, to the left of the solenoid is the pressure regulator for each slide bladder. With gauges installed, you can turn the allen screw adjustment in the top to set them as you please. I have my living room bladder at 7-8psi. I had to turn the bedroom slide bladder up to 14psi for it to completely seal out light all the way around. I'm thinking the lower the pressure the better, as long as it fully seals the gap.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #18 – November 09, 2021, 07:45:41 pm

Quote from: bpal – November 09, 2021, 07:37:12 pm

Not specific to your bladder issue but you might also want to check and see if this service bulletin was ever applied to your coach. Your build number is in range to be affected. Michelle had posted this at least one time before. I have the parts to apply the remedy to our coach but it hasn't made it to the top of the list yet.

Very interesting. Mine is in that range and does NOT have that done to it. I'll have to read more about what it does when I have a few minutes.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #19 – November 09, 2021, 08:24:56 pm

Quote from: WS6_Keith – November 09, 2021, 07:45:41 pm

Very interesting. Mine is in that range and does NOT have that done to it. I'll have to read more about what it does when I have a few minutes.

I had looked at it along with the air schematic and had decided it was a good idea but I don't remember the specifics anymore. I'll figure it out again when I install it and update documentation for the coach.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #20 – November 10, 2021, 11:40:21 am

Ref the manifold valves controlling air to the slide bladders: Any idea which valve controls which bladder?

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #21 – November 10, 2021, 03:06:13 pm

Quote from: WagonWheels – November 10, 2021, 11:40:21 am

Ref the manifold valves controlling air to the slide bladders: Any idea which valve controls which bladder?

Without gauges to see one increasing/decreasing pressure, about all you can do is have someone else turn the key to depressurize the bladder and listen/feel the solenoids to see which one opens. I guess you could turn off the input ball valve and then turn the key and see that one stopped whichever slide you turn the key for. For mine, the living room slide is the top and the bedroom slide is the bottom.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #22 – November 10, 2021, 07:11:41 pm

I experimented by turning the valves and determined the bottom valve controls the closet slide bladder. Valves leak badly, so bad that air gets by the bottom valve and eventually comes out the hole in the closet bladder seal. Bubbles on both valves, but the bottom valve creates more bubbles than the top valve.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #23 – November 10, 2021, 07:35:57 pm

Do you mean the 1/4 turn valve on the inboard side of the solenoid pack? If so, those are standard ball valves. You can buy a replacement set at Lowes for a few bucks each. That's what I did.

Re: 12VDC Thompson Air Compressor Will Not Turn Off

Reply #24 – November 11, 2021, 05:06:35 pm

Bought new 1/4 inch ball valves at Lowes this AM. Is the air line hose fitting flair or compression? I guessed flair when purchasing the connector from the ball valve to air line fitting. I hate compression fittings. Hopefully the connectors are not frozen and difficult to unscrew. Worse case would have to the connector break off in the manifold case.

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