My AC Won't keep blowing cold on my 2006 RV E-450 gas. I just replaced the high and low cut-off switches and when I put the pressure gauge on the AC, it said that everything was running perfect and it was running cold too. But then let it run for ten minutes and it stops blowing cold and now the pressure gauge reads above the high area into the yellow and headed towards red (too much pressure) and I can no longer hear the compressor kicking on and off. I actually let out some of the freon, since the gauge now read too high. But this has been a cat and mouse game for some time. We changed out the relays and that didn't help. It's blowing fine, there doesn't appear to be any vacuum leaks, as I've read about those (and it was running fine going up hills prior to this). Right now it's just sitting flat on my property and not even working the engine. No blockages. But it makes travel in summer months pretty awful. Any ideas?

If I had to take a guess. and given your post all I can do is guess.You need to clean the condenser coil.. On other than coleman this involves some work... First remove the outer cowl (Cover) on the A/C.. Generally this is about a dozen phillips head screws around the bottom (A magnetic parts tray is nice to keep track of 'em (Harbor freight, most auto stores, many hardware). Then you need to remove the INNER cover over the condenser.. This can be easy (A few more screws) or major (Cut the sealing tape. Unbend the tabs and so on) now you can see the crud blocking the thing.. You may need to pull the condenser fan (I did but I wear an xxl or xxxl glove) or use a soft brush to coax the crud off the fins...Then you get to put it all back together.Coleman instructionRemove 4 bolts (Philips head) from the top of the unit and lift off cowlPeal the condenser clean, replace cowl, replace bolts.

Thanks for the quick reply. Okay, if I didn't make myself clear, let me start again. This is the Chassis AC - the one installed by the Ford Chassis, not the roof mounted coach one. So this is the AC blowing out of the dash while you drive down the road.

backup a bit.You may have a worn compressor clutch creating too large of a air gap which often will engage for a short time then will disengage as the pressure in the system increases from heat.Verify that the compressor is staying engaged with the clutch, if the center part of the pulley stops spinning you have a worn clutch.Sometimes the center part of the pulley will still be spinning, but not as fast as it should and that is also a sign of worn clutch. To find out for sure, you will want to verify the clutch air gap. This is done with feeler gauges..Sometimes the air gap can be restored by changing/adding/removing shims.SEE HEREFound a good video on how to check the air gap, remove the clutch and how to adjust the gap..HEREMake sure the air gap is correct before trying other stuff..

My guess would be the expansion valve needs to be replaced. Probably should replace the receiver/drier also.

What are the pressures both low and high while it is cooling and what are they when they start going up and quits cooling? I'll venture a guess and say that the unit was low on gas and someone added some or too much and also did not do it properly and introduced some air into the system. Air in the system will cause what you're reporting. Also I don't think a dirty evaporator( someone called it a condenser) will cause this problem.What gas does your ac system use? Are you refilling with the sam? Maybe R134A?I doubt that the clutch is the problem.

AC Quits Blowing Cold after a few minutes | Good Sam Community

wa8yxm
Explorer III
May 02, 2022
adventureman5 wrote:
Thanks for the quick reply. Okay, if I didn't make myself clear, let me start again. This is the Chassis AC - the one installed by the Ford Chassis, not the roof mounted coach one. So this is the AC blowing out of the dash while you drive down the road.

Ah. well there are two types of Heater controls on vehicles. one is a simple air door that either directs air through the heater core or not. The other, far more common, is a water valve in the heater core line that lets hot engine coolant flow through the core.. or not.

And those valves can stick open.
ernie1
Explorer
May 02, 2022
Exactly my thought.
time2roll
Nomad
May 02, 2022
Best to have a professional get it working.
ernie1
Explorer
May 02, 2022
After replacing the high and low pressure valves was the system evacuated? Not evacuating the system after opening it and exposing it to air, not having the proper equipment like gauges and not knowing the proper pressures at the ambient temperatures will cause all kinds of problems. Prior to the attempt to charge the system had it been open and exposed to air? If so, the drier needs to be replaced, the system evacuated and hope the expansion valve or maybe the capillary tube, not sure which you have, is not plugged and needs to be replaced.
S_Davis
Explorer
May 02, 2022
Be careful venting refrigerant, you can get a hefty fine.
Gdetrailer
Explorer III
May 02, 2022
ernie1 wrote:

I doubt that the clutch is the problem.

I suspect that the clutch was the original problem. Clutch slippage is more common than one might think. Checking the air gap is very easy and quick to do.

When the air gap gets on the outer edge of the specs it can randomly engage or disengage without any warning or reason.

Often engaging initially when engine is cold then drive a couple of miles and no more cool air when the gap is just past specs. Reving the engine doesn't reengage, going faster doesn't help but often you can "bump" the center of the pulley and you now get cold air until the electric to the clutch is removed and you have to bump it again.

Have ran into that myself with a '03 Ford..

OP most likely added a new problem by adding refrigerant when it wasn't really needed (to much air gap mimics the same symptom as too low on refrigerant)which leads to overfilling.
lryrob9301
Explorer
May 02, 2022
time2roll wrote:
My guess would be the expansion valve needs to be replaced. Probably should replace the receiver/drier also.

This is the correct answer. Also make SURE you are not overcharging the unit, refill with the correct amount of R134 as per the manufacturer's instructions.
adventureman5
Explorer
May 02, 2022
Wow! Lots of ideas. Let me see what I can answer before I go check some more things to help answer....

Yes, using the same gas. R134A.

I'm pretty sure I did overfill it the first time. I assumed, probably wrongly, that it was low. Bought the gas and it said low, so I put in what the guy at Autozone told me to expect to put in. When it started kicking in the clutch, it shot up way too high. Now I had to let a whole bunch out and there is no good way to do that except to waste it while sitting in the parking lot....

Today pressure reading was spot on, until the clutch quit kicking on and off after I replace the high and low pressure valves.

I'll look at the pulley tomorrow....
ernie1
Explorer
May 01, 2022
What are the pressures both low and high while it is cooling and what are they when they start going up and quits cooling? I'll venture a guess and say that the unit was low on gas and someone added some or too much and also did not do it properly and introduced some air into the system. Air in the system will cause what you're reporting.

Also I don't think a dirty evaporator( someone called it a condenser) will cause this problem.

What gas does your ac system use? Are you refilling with the sam? Maybe R134A?

I doubt that the clutch is the problem.
time2roll
Nomad
May 01, 2022
My guess would be the expansion valve needs to be replaced. Probably should replace the receiver/drier also.