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2000 Dynasty Dash AC Compressor: not kicking on


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I decided to try to get my dash AC working. For the past 8 years we typically stayed away from real hot weather so I never bothered. I assumed it needed a freon charge so I started there. I started adding some and then realized that the compressor clutch wasn't engaging. Checked the 20A fuse in the FRB and it's good. Checked the relay in the RRB and it seemed fine but just in case I swapped that out with a new relay. Checking the legs of the relay, I doesn't seem that I have power coming from the dash switch to the relay. Anyone have any clues if maybe a sensor is telling the system to not turn on the compressor?

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When you "started adding some" how many oz / lbs did you add?  how did you measure how much added? 

The compressor won't engage until there's sufficient charge in the system.

- bob

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First a disclaimer... I'm pretty experienced mechanically but I know zilch about AC systems. I picked up a few cans of freon at NAPA including one with a hose and pressure gauge so I'm not working with high precision equipment.

I turned on the dash AC and then connect to the system. The pressure is indicating about 80 psi but little to no freon seems to be going into the system.

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Hi Mary/Glenn, Our AC was doing the same. Checked fuse and relay,  all good. There is a Thermostat Switch that is used to keep the Compressor from being damaged. It is located in the front where the Evaporator case is. Mine failed open so there was no power to relay and Compressor. You can find a replacement at NAPA or Frieghtliner. Study the attached diagram. Hope this is the problem. ja

34DF34AF-385D-49BF-B8DD-E816286CA984.jpeg

Edited by MrAmbassador
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80 psi is plenty high to turn the clutch on. Depending on ambient temp, your system might even be full and you will not be able to add any without it running. From what I read, you have an electrical issue to resolve first, between the dash switch and the relay and then to the clutch. No sense to try adding more until your clutch is running.

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1 hour ago, MrAmbassador said:

Hi Mary/Glenn, Our AC was doing the same. Checked fuse and relay,  all good. There is a Thermostat Switch that is used to keep the Compressor from being damaged. It is located in the front where the Evaporator case is. Mine failed open so there was no power to relay and Compressor. You can find a replacement at NAPA or Frieghtliner. Study the attached diagram. Hope this is the problem. ja

 

This is great ja... Does the part in the picture look like what you replaced? If so, can that be removed without depressurizing the system?

Thanks a bunch, Glenn

IMG_5473.JPG

Follow-up question... if that is the thermostat switch, does anyone have any comments regarding my jumpering across the leads as a test to at least see if that allows the compressor to kick on?

...now that I look at this more I see that it is a stat and not actually connected into the pressurized tubing. Feeling like this it the suspect piece and would be great to test if the jumper idea passes muster with y'all.

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My problem was the thermostat to the left of the the low pressure switch, but since it does not look like it has a switch, I would venture to say that what you circled the low pressure switch is probably the problem. If failed it will not provide the voltage to the Compressor. If you have a volt meter turn the key on and check for 12 volts on both connections. You should have 12 volts on both sides. If you only have it on one side the switch is bad (80 psi of Freon is sufficient to activate the switch.  If the switch is ground switch, then just check the Ohms across the two connections. With the key on there should be some residence if it is good, if not it would show an open circuit which means it has failed. Temporarily you can disconnect the switch and place a jumper wire across the connections. Start your engine and check to see if your Compressor engages, if it does the low pressure switch is the problem. Please don’t run the AC long with the jumper, you will eventually damage the compressor. Hope this helps. ja

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My 05 sig wouldn’t turn the compressor until I un plugged it and jumped a hot and ground to the compressor and once it was spinning it would take a full charge and after fully charged it worked fine. I believe you are unable to charge it if the compressor isn’t running. I am sure more damage is done to these coaches from not being used.

paul

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OK, so I took Ivan's suggestion and pulled the leads from the stat and attached a flat fuse... the compressor turned on and I was able to add 4 lbs of freon. This only got the pressure to around 12 psi. I have no clue when the system last ran. I bought the coach in 2012 and never ran the dash air so I'm guessing it will take a lot.

My assumption was wrong about the stat not being a part of the pressurized system... I started to loosen it and learned. Based on the comment above from Paul Busch, I'm wondering if the stat is fine and I just need to get it fully charged.

29 minutes ago, Paul Busch said:

My 05 sig wouldn’t turn the compressor until I un plugged it and jumped a hot and ground to the compressor and once it was spinning it would take a full charge and after fully charged it worked fine. I believe you are unable to charge it if the compressor isn’t running. I am sure more damage is done to these coaches from not being used.

paul

Paul, do you recall how much freon you had to add to fully charge? Thanks, Glenn

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I used just around 4lbs in our Signature. I can't imagine that you would need more but hard to tell without real gauges. You don't want to blow up the high side of compressor if there is no high pressure switch. My low side pressure at the compressor is lower than normally expected but high side is about right and it works fine.

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I forget but I just used the large cans from NAPA and filled till it was in the night green on the cans gage. I do think the damage comes from non-use. I had my used coach for 5 years and only used it a couple weeks a year and nothing worked. Started full timing last October and once everything is working it all got better. 1 of my air conditioners had no charge, one worked and one was semi cold. I tapped all three. Added leak sealer to one and jumped the compressor to get it to charge. Middle one was a full charge and front one took park of a charge. All are blowing ice cold air since January in Texas. 
the same with the engine compressor. Once I got it charged after hot wiring the compressor it has worked flawlessly since last November. Good luck

paulb

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9 times out of 10 there should be a Schrader valve on the hose connection in order to change out the switch. Don’t run the AC long with the jumper/blade fuse for long. It will eventually starve the Compressor and fail. You can buy that switch at any car part store. ja

Edited by MrAmbassador
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I believe the compressor will not run if the charge is to low and it will not charge without the compressor running. I could not get mine to charge without the compressor running. That is the dash and 3 roof top air conditioners.

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I'll pick up another 1 lb can tomorrow when I make the run to CO Springs. I'm sure its cheaper there then up here in our little mountain town. Hopefully it will do the trick and not need a new switch.

Thanks all you guys for chiming in with ideas, much appreciated.  Glenn

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Switch is probably just stuck.. they're not very reliable, especially if the system has had dirt or sludge in it. You'll want a new receiver/drier for sure if the system was flat for a long time. Did it have any pressure in it before you charged? Moisture in the system will cause the TxV to freeze and restrict the system, or form acids that will eat a hole in the evaporator; the presence of air causes high pressure spikes. No need to pull the system down to replace the switch as mentioned, but you'd obviously need to empty it to replace the receiver, which would find you needing a vaccum pump.

My switch is in an R134a system but the fitting Monaco used is for R12. Pressures are the same, but double check the threads. 

Edited by trailmug
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If your compressor does not kick in with 4 lbs now, I would save myself a trip and get a new switch also. And Bob's advice is good. You can rent the gauges and pump for free and get it right. Just my opinion.

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I bought a cheap AC gauge set off Amazon.  It works perfectly.

I added several 12 oz cans to the dash AC to get low side pressure up to 20 psi.  I believe 30 - 35 psi is the max but it wasn't increasing and I was getting nervous as overcharging can cause damage.  I'm getting 20F differential and that's about as good as it gets.   

If there was no charge at all you'll want to look for leaks at various junctions. 

- bob

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I was able to borrow a vacuum pump and gauge set from ORiellys. So tomorrow I get to add a new skill to my resume. Fingers crossed there are no broken components and all goes well. I did get a handful of schrader cores to replace the old ones. 

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Re: the receiver/dryer.. there's a cake of desiccant in it that absorbs any residual moisture. If the system lost its charge it would have taken on air/humidity and saturated the desiccant. You might be able to bake the old one in the oven in a pinch. If you do get a new one, you can cut open the old one to get an idea of the condition of the system. This is what mine looked like. Gross. That oil should be clear. 1585084113_IMAG121901.thumb.jpg.d0c6628423e7224c68c641a1ec0b2243.jpg

 

I hear you re: the new skill.. I ended up with a recovery machine, cylinder, and an EPA license out of working on our coach (charging liquid from a 30lb cylinder is way, way easier). 😛

Edited by trailmug
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6 minutes ago, trailmug said:

Re: the receiver/dryer.. there's a sack of desiccant in it that absorbs any residual moisture. If the system lost its charge it would have taken on air/humidity and saturated the desiccant. You might be able to bake the old one in the oven in a pinch. If you do get a new one, you can cut open the old one to get an idea of the condition of the system. This is what mine looked like. Gross. That oil should be clear. 1585084113_IMAG121901.thumb.jpg.d0c6628423e7224c68c641a1ec0b2243.jpg

I don’t recall seeing a round thing that size. I’ll check in the morning.  Is it up front on the outside of the firewall? Is it a readily available part? I live in the mountains with a tiny NAPA store for the ranchers. It’s a 2 hour round trip to the closest real town so getting parts isn’t super easy. 

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Should be something the size of a tall boy beer, between the condenser and the TxV (should be the other end of the hose you pictured earlier).

See if NAPA still has the MEI/AirSource catalog.. it has a ton of truck A/C parts. That's where I got mine. 

http://www.meicorporation.com/pdfs/Driers09.pdf

The switch is MEI 1512 or 1513, depending on the threads. 

If you're ordering parts, grab some oil, too.. The Sanden oil is MEI 8248 (presuming you have a Sanden compressor.. that info was in my coach info sheet). It's recommended to put a couple oz in the receiver if you replace it. 

Edited by trailmug
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48 minutes ago, Mary & Glenn said:

I did get a handful of schrader cores to replace the old ones. 

I may be wrong but I think those Schrader cores are different than tire valve stem cores.

Can anyone confirm?

- bob

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The scraders look the same to me, but I never paid them much mind.. their job is to keep the system from dumping when the cap / switch is removed, but otherwise they don't do a lot -- the O ring is the primary seal.

If you're pro, you use a core tool to remove them in order to make vacuuming faster but I've never bothered with it.

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8 hours ago, Mary & Glenn said:

I don’t recall seeing a round thing that size. I’ll check in the morning.  Is it up front on the outside of the firewall? Is it a readily available part? I live in the mountains with a tiny NAPA store for the ranchers. It’s a 2 hour round trip to the closest real town so getting parts isn’t super easy. 

Many coaches have the receiver/dryer located up front however my 03 Windsor has it mounted in the vicinity of the trans / differential,  up high.  I think I could see it from the bedroom floor opening.

Mine is a very common one available at my local parts store.

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