91 Mazda AC switch

I’ve got a 91 Mazda MX-6 LE in August with no AC. The air conditioner has not worked for a couple of years now. I have discovered that the problem is definitely electrical.

If I connect the compressor directly to the battery the whole AC system works beautifully, but that’s no solution. Both AC fuses, the one under the dash and the one in the engine compartment, are fine and run other 20 amp devices fine. The AC switch LED comes on indicating that it has power, but the compressor never gets the juice to engage. The AC wire goes in to a conduit with several other wires so I can’t exactly trace it. Anyone run in to something like this?

The compressor is also controlled by pressure switches connected to relays. You need to get a wiring diagram and go over it. Any of the relays and switches could be the problem. Similarly, one of the pressure switches could be working right and cutting off the relay because the pressure is too high or too low. If the former, you could blow up the compressor. Low pressure can also cause damage. Be careful with your jumper wires!

You need a service manual with a wiring diagram. If you don’t have a service manual you’re just guessing. Is there a relay for the AC compressor? I don’t know, but a service manual would tell you.

Or, you could take the car to an automotive AC shop and let them figure it out.

You have possibly diagnosed it correctly. Now you have to perform the finite. This is what seperates you from many others. You have to, have to trace those wires or pay somone else to perform what you suggest you cannot do. Just do it. Take your time and trace them. You will save dollars. You could also install new wires and switch but that requires the same knowledge you already possess, along with more labor and parts. I say find and fix the open loop in the circuit. you may also find a relay that you did not know existed.

I was being fececious about running jumpers to the compressor and I do not reccomend this for a fix due to the danger of high pressure overload. I got involved in cutting up and left out the safety first part. Be safe now.

You have to know both the high and low side pressures before you can say the AC works “beautifully”, what are the pressures?

By beautifully I just mean that cold air comes out and nothing sounds like it’s in pain. Don’t worry, I don’t run the AC. Jumping it off the battery was just done to shade-tree diagnose the thing. Thanks for the advice about the pressure. I’ll look up what the pressures are supposed to be. I’m hopeful that there’s just too much or too little pressure since that’d be an easy fix. I also think it’s likely because the car’s been converted to 134a and it’s very likely that I just put too much in last time.

Ok, so there wasn’t really any pressure to speak of, which would make sense since it’s been about 3 years since I charged it and I used to do it at the beginning of every summer. What are the odds I overcharged it last time I did it, so it wouldn’t come on and I didn’t use it. It then leaked slowly over the winter and was undercharged the next summer?