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Old 06-25-2022, 09:56 PM   #1
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Dash A/C Woes

I love my W22, but the poorly designed dash a/c has been an endless source of frustration. I've spent enough on it now to have been able to buy a whole new system if one were available.

I got tired of having to recharge it every summer, so two weeks ago I took it to a shop to track down the leak. They traced it to a hose and had a new one made. We just finished a four day drive from Arizona to Colorado and the first 2 days the a/c worked fine, not super cold but good enough. Day 3 it worked about half the day and then started blowing warm when we hit some traffic in a town. That's not unusual, but it normally starts blowing cold again when we hit the open road. Not this time, and it blew warm the rest of the day.

Next morning it was blowing cold again until temps got warm under the hood, and again this morning it did the same thing.

I installed a manual heater hose shut-off valve more than a year ago, so that's not the problem. Compressor was replaced about 18 months ago.. I suspected maybe high pressure is causing the limit switch to shut the compressor off, but have not actually been able to verify that, and if it were that (overcharged, for example) why would it have worked the first couple days, especially as ambient temps were higher those days compared to the last two?

Since we're at a campground for the next few days I'm looking for things that I can check while parked. Can the high limit switch be replaced without evacuating the system?

Any other ideas?
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Old 06-26-2022, 04:06 AM   #2
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Quote:
Originally Posted by CamJam1 View Post
I love my W22, but the poorly designed dash a/c has been an endless source of frustration. I've spent enough on it now to have been able to buy a whole new system if one were available.

I got tired of having to recharge it every summer, so two weeks ago I took it to a shop to track down the leak. They traced it to a hose and had a new one made. We just finished a four day drive from Arizona to Colorado and the first 2 days the a/c worked fine, not super cold but good enough. Day 3 it worked about half the day and then started blowing warm when we hit some traffic in a town. That's not unusual, but it normally starts blowing cold again when we hit the open road. Not this time, and it blew warm the rest of the day.

Next morning it was blowing cold again until temps got warm under the hood, and again this morning it did the same thing.

I installed a manual heater hose shut-off valve more than a year ago, so that's not the problem. Compressor was replaced about 18 months ago.. I suspected maybe high pressure is causing the limit switch to shut the compressor off, but have not actually been able to verify that, and if it were that (overcharged, for example) why would it have worked the first couple days, especially as ambient temps were higher those days compared to the last two?

Since we're at a campground for the next few days I'm looking for things that I can check while parked. Can the high limit switch be replaced without evacuating the system?

Any other ideas?
Hello, sorry for your issues. Sounds to me like there is still a leak in the system. Very hard to locate and fix leaks on any a/c. I personally use an electronic leak detector which helps me locate hard to find leaks on most a/c. It's quite possible that there is a possible leak in the condensor or evaporator and as I said before these leaks are extremely hard to find. I know this doesn't help right now but I would ask the service company that serviced the unit to leak check and put a set of gauges back on your a/c to trouble shoot so you can narrow down the issue. Good luck
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Old 06-26-2022, 06:53 AM   #3
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Cam, Chasing small leaks in your A/C can be time consuming and expensive if you pay for it. You might visit Harbor Freight and buy a gauge set. See Guages.

Then you need a temperature vs pressure chart like the one attached to this post.

This allows you to do 2 things. With them you can be sure that the A/C system is charged with the correct amount of R134a and you can determine if the system is leaking over time.

If it is leaking the gauges will not help you find the leak. To find the leak you might buy a Leak Detector.

If you should need to add refrigerant you will need a Tap Valve.

If you are going to have old vehicles this stuff is the opportunity to learn something new, save some money, expand your hobby and...just maybe make you smile when you solve a problem.
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Old 06-26-2022, 07:15 AM   #4
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Cam - the compressors GM used on these units have an inherent flaw in them where they start leaking around the belly of the compressor.

Ours had the same problem and I was suspect of a refrigerant leak when we bought the coach in Jan ‘21.

Then last September after the main wiring harness fell against the compressor - and ruined the compressor clutch (a whole other story) - I replaced it with a new Sanden compressor.

You can see in the picture of the compressor where PO’s had dye put in the system. You couldn’t see this from the top of the compressor with it installed.

It was in doing research for the compressor that I learned of the design flaw.

Being suspect that I did have a leak I did do some digging around in my system trying to find signs of oil leaking at all the connections.

There are 2-3 places on the Net that do have many of the system components. I have found parts through Acme Air Parts, Mill Supply, ComfortAirGr, Victory Climate Systems, and nwrvsupply. And while I have not bought from them, they did give me enough information that I could better understand the evolution of MoHo dash A/C.
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Old 06-26-2022, 09:22 AM   #5
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Thanks to all who responded. I do own a leak detector, though not with me, and I have just enough experience with installing, evacuating and recharging a/c to realize it's best left to the pros. Agreed that you really need gauges to troubleshoot why it's blowing warm. The trip home to AZ won't be much fun without a/c, which is exactly why I had it serviced before I left . Fortunately, the generator has been performing perfectly since I replaced the carburetor, so we'll probably just have to run the coach a/c all the way home. The cats start yowling when they get hot, which only adds to the enjoyment.

I might just get a cheap Auto Zone recharge kit in the meantime, which will at least let me see what the low-side pressures look like.
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Old 06-26-2022, 11:00 AM   #6
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Did not get a recharge kit that includes a sealant. Sealants cause more issues than they solve when it comes time subsequent repairs.

You will probably be safe to add a can but keep in my new R134 systems are touchy about overcharging.

As for the prior repairs - they didn’t do you any favors. A proper vacuum can not be pulled on a repaired system that leaks. You must hold 500 microns or less vacuum for 30 minutes to consider the system leak free.
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Old 06-26-2022, 11:31 AM   #7
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Simple on the road tests that take no tools.. 1.. check compressor is coming on. . .?. 2.. under hood at evap box.. one hand on low side.. is it cold? 3.. hand on HIGH side. Is it hot? Report back to us.. check fans are coming on ?

Next buy a book on basic automotive a/c that covers gm/Chevy.. it will more than pay for itself.. next.. check the new hose they put in.. see if any oil stains .. try and see if it is tight..
Next.. find better shop.. no offence.. but sounds like they just rush you in and out.. look and see.. if they replaced the filter/dryer .. if not.. they should have..

So if at evap box.. compressor running.. you find one hose hot and one Jose cold.. then could be blend doors.. if both same.. could be expansion valve or evap temp control.. oh.. are your electric fans for a/c coming on too?

This is why so many of us do our own.. because there are no competent shops.. they just don't fix it.. so you have to pull on your shop hat.. and go at it..
When is last time you had blower out and looked in there for nests? Report back to us and more opinions will follow
Good luck and keep us posted
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Old 06-26-2022, 01:23 PM   #8
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Simple on the road tests that take no tools.. 1.. check compressor is coming on. . .?. 2.. under hood at evap box.. one hand on low side.. is it cold? 3.. hand on HIGH side. Is it hot? Report back to us.. check fans are coming on ?

Next buy a book on basic automotive a/c that covers gm/Chevy.. it will more than pay for itself.. next.. check the new hose they put in.. see if any oil stains .. try and see if it is tight..
Next.. find better shop.. no offence.. but sounds like they just rush you in and out.. look and see.. if they replaced the filter/dryer .. if not.. they should have..

So if at evap box.. compressor running.. you find one hose hot and one Jose cold.. then could be blend doors.. if both same.. could be expansion valve or evap temp control.. oh.. are your electric fans for a/c coming on too?

This is why so many of us do our own.. because there are no competent shops.. they just don't fix it.. so you have to pull on your shop hat.. and go at it..
When is last time you had blower out and looked in there for nests? Report back to us and more opinions will follow
Good luck and keep us posted


X2 on the valve for the dash heat. It doesn’t take much coolant flow thru the dash air heater core to offset the A/C. It happened on ours - and the heat control knob on the dash is cracked at the stem making even harder to insure the valv is closed tight.
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Old 06-27-2022, 09:24 AM   #9
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Simple on the road tests that take no tools.. 1.. check compressor is coming on. . .?. 2.. under hood at evap box.. one hand on low side.. is it cold? 3.. hand on HIGH side. Is it hot? Report back to us.. check fans are coming on ?

Next buy a book on basic automotive a/c that covers gm/Chevy.. it will more than pay for itself.. next.. check the new hose they put in.. see if any oil stains .. try and see if it is tight..
Next.. find better shop.. no offence.. but sounds like they just rush you in and out.. look and see.. if they replaced the filter/dryer .. if not.. they should have..

So if at evap box.. compressor running.. you find one hose hot and one Jose cold.. then could be blend doors.. if both same.. could be expansion valve or evap temp control.. oh.. are your electric fans for a/c coming on too?

This is why so many of us do our own.. because there are no competent shops.. they just don't fix it.. so you have to pull on your shop hat.. and go at it..
When is last time you had blower out and looked in there for nests? Report back to us and more opinions will follow
Good luck and keep us posted
I really appreciate the detailed response. Had already tried to access the compressor but doesn't look like I can even see it without removing the dog house. In any case, we're presently at one of those unpleasant places that markets themselves as a "resort" and has strict rules about working on vehicles, so it will be later in the week before I can do anything further.

Fans seem to be turning, but not all that fast. Are they variable speed fans or not?
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Old 06-27-2022, 05:12 PM   #10
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I doubt they I’ll see you pulling the doghouse cover unless you leave the curtains open.

On our coach, that’s the only way to get to the compressor - and I suspect most Workhorse powered coaches due to the air dam above the radiator.

The condenser fans are single speed and pull know it when the come on. I do t recall at the moment if they are computer controlled or cycle with a head pressure switch. I think they are controlled from the ECM. Look in the Workhorse service manual or I think the fan control has been covered on IRV2 in another thread.
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Old 06-29-2022, 08:07 AM   #11
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Just hasn't been a convenient time to do it. We've been attending a family reunion, so staying busy with that plus have two cats with us that would have to be contained to remove doghouse. Currently in the mountains near Breckenridge, CO, but heading back to lower elevations starting today so would like to get this resolved. Will finally have some time tomorrow.
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Old 06-29-2022, 12:40 PM   #12
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We’re headed that way from Dallas next Tuesday - Westcliffe, CO.

Cats can be contained? ��
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Old 06-30-2022, 06:36 AM   #13
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We’re headed that way from Dallas next Tuesday - Westcliffe, CO.

Cats can be contained? ��
Ours are pretty good travelers, but they certainly let us know when they're not happy.

Yesterday we started out in Breckenridge at around 9,000 feet elevation. A/C worked perfectly. I had an infrared thermometer with me and would watch the air temps coming out of the vents drop from 75 degrees to high 40s whenever I switched from vent to Max AC. I monitored it this way all the way down the mountain, and everything was working fine until about 3/4 of the way to Grand Junction, which is of course a lot lower in elevation and warmer. Once the ambient temperature got in the high 80s the dash a/c quit blowing cold. I'm sure that the compressor was not starting when this happened because normally you could watch the vent temp drop as soon as switched from vent to MaxAC, but once it decided to shut down there was no change at all.

So why is it shutting down? My guess is high head pressures at high ambient temps. I have not seen the twin condenser fans come on yet, though we were at highway speeds all day so would they be a factor at those speeds? I did check the fuses and swapped relays around and didn't see anything amiss. I do plan to check the fans directly with 12V today to see whether they are good.

I do have a manual coolant shut-off valve installed, so we can eliminate that as a possibility. In any case, the system worked perfectly until it didn't, rather than watching vent temps slowly creeping up. Something is shutting the compressor down when the ambient temp gets high.

I thought I might just try replacing the high pressure sensor. They're relatively inexpensive and we have several auto parts stores nearby. I believe our sensors are common GM parts.

Could my system be overcharged? I'm in the dark on this, here at a campground, without gages.

I've also read about the Evans temp sensor thermostat being a source of failure (mentioned by donr103 earlier), this being the one with the semi-rigid probe that sticks into the evaporator. Not sure how easy these are to find.

Of course, the deficiencies of these systems has been well documented over the years. The transmission cooler really should not be in front of the condenser, and I do hope to address that over the winter.
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Old 06-30-2022, 09:52 AM   #14
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Could be.. bad relay.. grounds.. or compressor clutch.. or corroded connections.. without gauges.. all just WAG.. could be nest in blower housing.. critters find old rv tasty wires and rubber hoses and lines on rv and eat.. short and nest.. so when things go haywire and don't make sense keep critters in the back of your mind all the time..
But we need gauges to give you better opinions.. could be the filter/dryer getting plugged up.. have you done tests .. I stated above.. what where the results ?

Just don't jump around.. follow directions.. or you will be replacing everything..
Trans cooler upfront is best for trans.. don't change that.. also.. get great flashlights and look between condenser and radiator.. nest and trash get in there..
Good luck and keep us posted
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