Dash AC intermittently blowing cold air, then hot

[mhbell]

Dash AC intermittently blowing cold air, then hot

My Dash AC blows cold air when the engine is cold, but after it gets warmed up it blows hot air. I assume that it has a Evans Tempcon Electronic Coolant Valve that can shut off the coolant to the heater core when the dash AC is turned on. There is also a Vacuum Pot on the bottom of the AC shroud which I think operates a flapper blending door between the heater core and the AC. With the engine cold and idling, I get cold air. But going down a flat highway engine not under load I get hot air. Pulled into a rest area and with engine warm, and at idle I still get hot air. Is it the Evans Coolant Valve that is bad, or something in the controls. I have heard that some replaced the valve with a manually operated ball valve to use during the summer months. Can anyone shed some light on this and is there a way to check it out.
Mel

[fourmat]

mhbell wrote:

BTPO1 wrote:
I had that problem with my Rexhall with the Evans Tempcon Electronic Control. It got to where the control would not shut off after getting hot. I solved the problem by replacing the electronic controlled valve with a cable operated valve. Have not had any problems since. It was a fairly simple conversion for me, for someone that is not mechanically inclined it may be very difficult as the control panel must be modified or a cable control panel be purchased. JMO

It is not the Valve here is what I did.

I guess it must be a Vacuum leak I put a temp shutoff valve and tested the electronic one. It is opening and closing like it should when I change the temperature control. When hot is selected valve is open, When mid point is selected it is half way open, when in the cold position it is closed. So the Evans coolant valve is working. I had the same problem using the temp shut off valve that I installed. Got to be a vacuum leak or else the door flapper is not working. The sight glass is running clear and no bubbles so I don't think it is low on freon.There is a vacuum pot on the bottom of the AC case which I think is the flapper door actuater. I could not get any vacuum out of the line that is attached but when I remove it and put it back on I can hear a sound like something is moving. I will start tracing lines tomorrow. And check to be sure the compressor is running. Hope I dont have to tear into the dash. Someone in another thread said the they vacuum pot is located by the brake system and is part of it. I am trying to do the easy things first. tearing into the dash control will be a bearcat as the whole center section bezel has to be removed. Cant get under it to access the AC / Heater control panel.
Mel

Mine did the same but it was still not shutting the coolant flow off. Try putting a clamp on the coolant hose and see if a/c gets cold if it does replace the valve

[mhbell]

BTPO1 wrote:
If you have access to a hand vacuum pump it would be handy to check the vacuum doors. I have seen the diaphragms go bad before. Another thought is that if there is a vacuum leak most systems default to the windshield defrost position for safety.

Yes it does sound like the valve is not the problem. In my case the valve would close off completely when it was cold, but as soon as the coolant warmed up some it would close but stay slightly open. It was enough to allow hot water to flow through and give hot air flow.

Hope when you find your problem you will let us know what you found.

I will see about getting a hand Vacuum pump. I am sure it is a Vacuum leak because this morning I checked the compressor and the clutch is working. I had the curtains drawn for the windshield and after checking the Compressor I noticed the curtains were moving above the defroster vents, So now I have to assume there is a Vacuum leak somewhere. Hope I don't have to tear into the dash. If I remove the doghouse I may have enough room to get into the underside of the dash by the AC / Heater controls. Got my fingers crossed.
Mel

[rkentzel]

This may help if you cant find the vacuum leak

[BTPO1]

If you have access to a hand vacuum pump it would be handy to check the vacuum doors. I have seen the diaphragms go bad before. Another thought is that if there is a vacuum leak most systems default to the windshield defrost position for safety.

Yes it does sound like the valve is not the problem. In my case the valve would close off completely when it was cold, but as soon as the coolant warmed up some it would close but stay slightly open. It was enough to allow hot water to flow through and give hot air flow.

Hope when you find your problem you will let us know what you found.

[mhbell]

BTPO1 wrote:
I had that problem with my Rexhall with the Evans Tempcon Electronic Control. It got to where the control would not shut off after getting hot. I solved the problem by replacing the electronic controlled valve with a cable operated valve. Have not had any problems since. It was a fairly simple conversion for me, for someone that is not mechanically inclined it may be very difficult as the control panel must be modified or a cable control panel be purchased. JMO

It is not the Valve here is what I did.

I guess it must be a Vacuum leak I put a temp shutoff valve and tested the electronic one. It is opening and closing like it should when I change the temperature control. When hot is selected valve is open, When mid point is selected it is half way open, when in the cold position it is closed. So the Evans coolant valve is working. I had the same problem using the temp shut off valve that I installed. Got to be a vacuum leak or else the door flapper is not working. The sight glass is running clear and no bubbles so I don't think it is low on freon.There is a vacuum pot on the bottom of the AC case which I think is the flapper door actuater. I could not get any vacuum out of the line that is attached but when I remove it and put it back on I can hear a sound like something is moving. I will start tracing lines tomorrow. And check to be sure the compressor is running. Hope I dont have to tear into the dash. Someone in another thread said the they vacuum pot is located by the brake system and is part of it. I am trying to do the easy things first. tearing into the dash control will be a bearcat as the whole center section bezel has to be removed. Cant get under it to access the AC / Heater control panel.
Mel

[jplante4]

Had pretty good luck with these guys.

Thermotion

[1gvols]

Replace the valve.

[BTPO1]

I had that problem with my Rexhall with the Evans Tempcon Electronic Control. It got to where the control would not shut off after getting hot. I solved the problem by replacing the electronic controlled valve with a cable operated valve. Have not had any problems since. It was a fairly simple conversion for me, for someone that is not mechanically inclined it may be very difficult as the control panel must be modified or a cable control panel be purchased. JMO