AC works, but will not turn on/off inside car

[maxima278]

I'll need to go to pep boys and buy some big a$$ tail pipes to stick out the back so I can be extra convincing!

[maxima278]

yesterday after I put power to the relay, I tried grounding the other side of that relay and I still got nothing. Is that different from what you asked me to do?

[NISTECH]

no and that is almost uncomprehendable. theoretiucally that is the same as what you did initially by jumping the relay terminals to turn on the compressor. what that says now is the relay is bad. You did swap that relay out right???

[NISTECH]

have you by chance blown the fuse for the a/c compressor??

[maxima278]

I'll check the fuse again, but I just jumpered the relay again yesterday morning and it worked. I have a couple of relays I have swapped in and out. I guess I will try it again with the other relay.

[maxima278]

apparently I have a good relay and a bad relay. I got it to work. I will run wires for a toggle switch or button as you said. After this much trouble I think I can live with that. Thanks very much for all your time and all your help. I don't think I can thank you enough!

[NISTECH]

hold up. just supply the power to the relay as we discussed . do nothing else and test the system. I bet it works. you wont need the toggle switch if thats the case.

[maxima278]

I've already tried it but will definitely try again before I run the switch. I will probably put it under my dash so that I don't have to drill any holes. Will it cycle this way? Or does it really need to?

[NISTECH]

As long as your still using the pressure switch it will cycle on and off.

[loystock]

I'm sorry for the intrusion, gentlemen. I have a related problem on my daughter's 94 Sentra. After replacing the expansion valve, the compressor won't automatically cut in anymore. Compressor works when A/C relay contacts are jumpered. All other components are Ok so it's either the ECM or the Thermo Control amplifier that is bad. My questions are: 1) What is the quicjkest way to isolate if the problem is the ECM or TCA; 2) Is the ECM from Hawaii compatible with California standard? A new ECM from Scottsdale Infiniti is @ $400 while a used one from HI will only cost me $40.

Thanks,Rod

[loystock]

I'm sorry for the intrusion, gentlemen. I have a related problem on my daughter's 94 Sentra. After replacing the expansion valve, the compressor won't automatically cut in anymore. Compressor works when A/C relay contacts are jumpered. All other components are Ok so it's either the ECM or the Thermo Control amplifier that is bad. My questions are: 1) What is the quicjkest way to isolate if the problem is the ECM or TCA; 2) Is the ECM from Hawaii compatible with California standard? A new ECM from Scottsdale Infiniti is @ $400 while a used one from HI will only cost me $40.(please see attached)

Thanks,Rod

[maxima278]

I'd wait for Nistech's reply on this if I were you, but if you look back through this entire ordeal somewhere in there you will find where he told me how to bypass the thermo control amplifier. As for the ecm, if nistech says it will work in your car, then by all means get the $40 one. Even if yours isn't bad, odds are you could run into problems in the future and at least you will have a good one to test yours against. If it won't work, post on parts and equipment boards until you find one that will work. No need to pay $400 for that ever! Junkyards are full of early 90's Sentras (namely pullapart in GA). Just don't do what I did and get parts from a different year model because they seem to change electrical things regularly.

[NISTECH]

Testing the thermal control is the same basic test as mentioned here, wire colors are different though. I seriously doubt its the ECM.

[loystock]

I did not buy the Sentra ECMs on sale at eBay since they have Federal configurations which are not compatible with CA cars (pinout of the connectors are opposite). It took me a while to fix the problem, not having a schematic diagram specific to the ’94 Sentra. All of the voltage and continuity testing were Ok but the compressor clutch still won’t engage. I finally traced the problem to a loose contact on the dual pressure switch connector. Seems like the lead wire is coming off the contact pin and continuity is only established when pressure is applied on the connector. I did a patch by using electrical tape on the harness. Now my next project is to find a connector from the salvage yard.

Thanks a lot, gentlemen, especially to Scott.

Rod