2002 Holiday Rambler Class A - Workhorse 20,000 miles.DASH A/C BLOWS HOT AIR AFTER ENGINE WARMS UP.So far I bypassed the heater hoses with valves. Replaced : New AC Delco compressor, expansion valve, expansion drier and 2 new switches which were hard to find since the compressor switch is out of production,but my Chevy dealer found one at a warehouse for me. I evacuated the system, check for leaks with machine (I have a shop) and we charged it with 2.75 lbs of freon. It worked great - a/c was ice cold. Week later went on a trip - and after 3 hours of driving turned on the a/c to see if it was cold - it blew HOT AIR and never got even cool. Got home, After we unpacked I waited about 3 hours and tried it - now the engine is cold and the A/C blew Ice Cold. Don't get it- why would it blow hot air only when the engine is hot and the heater hoses are bypassed with a valve - and blows cold when the motor is cold?? Can these bypass valves go bad? I used them all the time and never had one go bad on me. I am thinking of taking off the bypass valves and just making a loop with the heater hoses. Also above the heater hoses was a switch - I disconnected it to see if maybe that was causing the hot water to flow past the bypass valve if that is possible.... We are going away again in 2 week and could use the A/C.. Any ideas? Also is 2.75 lbs enough?? I called Monaco and one tech said 2.75 and another said 4 lbs/ Workhorse said that it has nothing to do with them. There is no label that has this info on it on the parts. It is a frigette.

I have exactly the same problem on my 95 Newmar - I have just installed 2 ball valves on the inlet and outlet from the heater matrix. Haven't had a chance to test it yet but I too was surprised that the AC blew red hot air even with a brand new water heater valve that was fully closed.It's a pretty simple system so where was the heat coming from if not from the water hoses? If it was just warm I would say it was from the engine compartment, but it was "full on" heater hot.

My gasser...the a/c cuts out sometimes when climbing a hill or under certain loads. But EVERYTHING cuts out. Fan, too. It's the vacuum. The vacuum cylinder is not large enough to to do the job under some stressful conditions. So the computer, I guess, shuts the system down to give the motor what it needs. I was told that Ford had a larger vacuum cylinder for sale...and I figured, "OK, next year I'll put that in." But..."next year" comes and goes.

jerseyjim wrote:My gasser...the a/c cuts out sometimes when climbing a hill or under certain loads. But EVERYTHING cuts out. Fan, too. It's the vacuum. The vacuum cylinder is not large enough to to do the job under some stressful conditions. So the computer, I guess, shuts the system down to give the motor what it needs. I was told that Ford had a larger vacuum cylinder for sale...and I figured, "OK, next year I'll put that in." But..."next year" comes and goes.Install a 12 volt vacuum pump, like the Diesels have. Much more reliable than replacing or adding an extra reservoir. Doug

http://www.evanstempcon.com/tsg_RefrigerantChargeGuide.phpCopy and paste for the amount of 134a. Not SCS Frigette, but the parameters are the same.Do NOT install a bypass. Clamp off BOTH heater hoses to the heater core and retest with hot engine. I will bet it blows cold. The ONLY thing that will cause your problem (IF the compressor is running) is hot water leakage thru the Heater core. Doug

Most of the P series chassis have the Evans tempcon valve and is a common cause for the symptoms described.The way to test it is to have the engine up to temperature with the heat totally off. If the hose going to the heater core is hot on the outlet side of the valve it has failed and needs replaced.www.evans.com

Dash A/C Blowing HOT air after engine is hot | Good Sam Community

14 Replies

dougrainer
Nomad
May 28, 2013
http://www.evanstempcon.com/tsg_RefrigerantChargeGuide.php

Copy and paste for the amount of 134a. Not SCS Frigette, but the parameters are the same.
Do NOT install a bypass. Clamp off BOTH heater hoses to the heater core and retest with hot engine. I will bet it blows cold. The ONLY thing that will cause your problem (IF the compressor is running) is hot water leakage thru the Heater core. Doug
dougrainer
Nomad
May 28, 2013
jerseyjim wrote:
My gasser...the a/c cuts out sometimes when climbing a hill or under certain loads. But EVERYTHING cuts out. Fan, too. It's the vacuum. The vacuum cylinder is not large enough to to do the job under some stressful conditions. So the computer, I guess, shuts the system down to give the motor what it needs.
I was told that Ford had a larger vacuum cylinder for sale...and I figured, "OK, next year I'll put that in." But..."next year" comes and goes.

Install a 12 volt vacuum pump, like the Diesels have. Much more reliable than replacing or adding an extra reservoir. Doug
jerseyjim
Explorer
May 28, 2013
My gasser...the a/c cuts out sometimes when climbing a hill or under certain loads. But EVERYTHING cuts out. Fan, too. It's the vacuum. The vacuum cylinder is not large enough to to do the job under some stressful conditions. So the computer, I guess, shuts the system down to give the motor what it needs.
I was told that Ford had a larger vacuum cylinder for sale...and I figured, "OK, next year I'll put that in." But..."next year" comes and goes.
havasu
Explorer
May 27, 2013
I have exactly the same problem on my 95 Newmar - I have just installed 2 ball valves on the inlet and outlet from the heater matrix. Haven't had a chance to test it yet but I too was surprised that the AC blew red hot air even with a brand new water heater valve that was fully closed.

It's a pretty simple system so where was the heat coming from if not from the water hoses? If it was just warm I would say it was from the engine compartment, but it was "full on" heater hot.

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Dash A/C Blowing HOT air after engine is hot

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