Air conditioner/heater problem

My 1990 Lincoln Town Car's air conditioner and heater are not functioning correctly and I would really appreciate some help. When I have it on "Air Conditioner", it will operate fine for awhile, then (on its own) start putting out hot air - and I usually can't get it back to cooling. Sometimes when I have the "Heater" on, it works for awhile, then cold air starts coming out and I can't get the heater to come back on.
Can you help with any comments or suggestions?
Thank you very much.
William Henry

These kinds of problems are often difficult to diagnose. A good Factory Service Manual would be a good thing to have as it has a trouble shooting guide for the Climate Control system.


eBay is a good place to find one they can be had in print or on CD. Or you could go to Helm publications and get a new book but it is pricy.

These kinds of problems are often difficult to diagnose. A good Factory Service Manual would be a good thing to have as it has a trouble shooting guide for the Climate Control system.


eBay is a good place to find one they can be had in print or on CD. Or you could go to Helm publications and get a new book but it is pricy.
Thank you very much.

Thank you very much.

I had a similar problem with my 88 TC. Just at random I would get hot air out of the a/c and the heater wouldn't work at all. With the help of a guy at autozone and the repair manual, we tracked it down. It was a in-line sensor on the heater hose(from the front of the engine look to the left of the plenum). In my case it had been bypassed all together which caused all kinds of problems since hot water was running through the system all the time. So, $12 later I put a new one on and it seemed to fix the problem. I also replaced the pressure sensor on the a/c accumulator too which was about $12 because it would get stuck in the 'off' position which of course cut off the compressor. Don't know if any of those suggestions will help but it's a cheap place to start.

Thank you so much. I will try that.