On my '98 Windstar the rear A/C is blowing hot air. Additionally the air is coming out of the incorrect vents, the ones that the heat normally comes out of.

It appears that the valve under the rear A/C unit is vacuum actuated, and I would assume that the louvers to control the air flow are also vacuum actuated. If this is correct, I would assume that I have a vacuum problem? However if it was a vacuum leak wouldn't the performance of the vehicle also show this?

Any help would be greatly appreciated!

 

I had the same problem on a full size van once, and found the vacuum operated valve that shuts off the hot water to the rear heater core was defective.

 

Would this also be why the air is coming out of the incorrect vents? Is the air flow damper also vacuum actuated? How do you check out the flow control valve to see if it is working or not?

Thanks

 

not sure on that particular van. some vans have a water control valve actuator. if not maybe also check the rear controller if
equipped. some just control temp door which if not working defaults to hot.

 

I have the same problem. Did you resolve you problem? I believe it is a vacuum problem. I measured 4 in Hg at the hose going to the air flow damper - not enough to change the air flow when the air conditioner is on so the air comes out the bottom (heater) vents. I am not sure what the vacuum level should be here. Must be a leak somewhere.

 

Kangaroo:

Yes I solved the problem. Replaced the rear control switch in the dash and it solved the problem. The switch is a combination electrical/vacuum switch. The fellow at the parts room new exactly what the problem was and was sure enough of it to warrant an electric part should it not be the culprit! Must be a pretty common part to fail.

 

Thanks. I will give it a shot. This is the switch in the front dash and not the controls in the rear?

 

That is correct it is the switch in the front dash. It allows you to control the function of the fan from the front or to transfer control to the rear mounted switch. Hopefully that is it, easy fix probably less than 30 minutes.

 

OK got the switch out - only that particular switch and not the whole bank of switches. Pretty easy. Did you purchase the new part at a dealer - do you remember the price range? Thanks.

 

Yes I purchased the switch at the dealer. I believe it was about $30.

 

I've got the same problem and want to try replacing the subject switch, but not sure how to get to it. Does the dash "cover" pop off somehow and reveal easy access to this switch?

thanks!

 

I have a problem with my back AC blowing hot air in back vents I was going to try and repair but it started blowing cold air then after I stared to drive it for about 30 mins the air started getting hot can any one help me out here

 

I realize the original post was a number of years ago, but I figured people were still having this issue and wanted to share what I did to fix mine. I have a 2003 e250 Econoline custom van. I noticed the problem was I was getting no air coming out of the vents in the front, just on defrost. I was also having the issue described in the original post of no rear heat even though the air was blowing through the vents.
The the front vent issue was a vacuum hose connected to the reservoir tank had gone bad. The problem is the only way to get to the reservoir tank and replace it is to take the entire dashboard out, so I bypassed it and installed a secondary reservoir tank. As soon as that was hooked up and it restored vacuum to the system, I have my front vents immediately.
The second issue was rear heat. In the rear of the van I have a second blower motor, and the blue vacuum line that runs from the front dash goes to the back and connects to a control module in the back. That blue line was not holding a vacuum and was not switching the blend door that controls the temperature to the rear fan. I disconnected the blue hose under the dash and from the rear module. I ran a new vacuum line as a replacement, and it worked instantly. It is still a long ways for the hot air to get back, so it does take a little while for the air to truly get warm coming out of the vents... Idling it just barely gets warm but whenever I'm driving it does heat up the rear of the van.