My car was overheating and a mechanic misdiagnosed the problem and replaced coolant bottle, gasket and thermostat. That did not help but I noticed that when I drive with AC off I don’t have the overheating problem.

I went back to this place and told him that I still have the same problem and he told me that I need to replace AC Compressor and Receiver Drier in order for my car to work properly.

I did not do it and I have been driving with the AC off and everything was ok.

I had to do some other repair on my car in the meantime and they replaced a serpentine belt for “with no AC” version to bypass the AC. After that the car is blowing warm air and AC does not work.

I will try to give you an idea what the original problem might be:

The engine works in “2 separate modes”

MODE A: AC Button off – everything is ok as long as that button is off inside the car. There is another button next to it with the option of air circulating inside the car etc and that does not make any difference. The car can be blowing either cold or hot air, it can be blowing it on 1 or it can be all the way to the end of the scale at 4 and that does not make any difference as long as that AC button is off.

MODE B: AC Button on – When I had it on in the summer time the engine was overheating (I guess the outside temperature was some sort of factor as well, I live in Las Vegas and it gets very hot outside). I don’t have the overheating problem right now (beginning of October when it is not hot anymore) but the engine is acting like this:

When I drive (and have the AC Button On) the engine is acting strange and the RPM meter is indicating it. I have a stick shift and I was getting the car to go 60MPH and then just putting it into neutral gear, taking my feet off all the pedals etc and just letting it roll by itself. The RPM meter was going down to about 1 then it was starting going up all the way to 4 ½ (just by itself, without doing anything with the pedals etc), staying there for a while (you could here the engine spinning like that etc, just like I would be holding my foot on a gas with no gear etc) and then coming back to 1. After about 3 seconds it was doing exactly the same thing, going back to 4, staying there for a while and spinning and then coming back down.
I also tried turning the AC button off when the RPMs were high like this (4 ½) and that makes the engine come back to the mode A immediately, when everything is working fine (it does not stay at 4 ½ etc – it is just coming back to normal as soon as I turn it off).

This is indicating the problem that I had from the very beginning and it was not diagnosed properly. I disputed the transaction with the credit card company and I am trying to get around $300 back from the place that did not diagnose the problem and just started replacing parts etc.
I was at a local dealership and I was lucky to discuss the whole situation with the service manager there and he told me that with something like that they need to check for Idle Speed Control Problem (RPM too high) and that it can be either bad sensors, wiring or the computer.

The main problem is that I don’t understand how this ORIGINAL PROBLEM is related to my AC not working (I know that they bypassed it etc, but it should be fine as long as I fix this one, but it does not seem that way) and to overheating problem. I also have 7-10 days to send a good paperwork explaining and describing the problem to my bank in order to try to get my money back and it all seems to be a little confusing.

I don’t have to fix my car right now because I am not going to be using AC for another 6 months or so and I don’t want to spend money on that also. I can just drive like that for now. On the other hand I need to know exactly what needs to be done to fix my car and also have some sort of idea how to prove my case to the credit card company or to the judge if I’ll have to go to the court with the person who misdiagnosed the problem and charged me for unnecessary repairs.

Thank you in advance for any info you can offer.