How can I install a toggle switch for the AC?

speedbump · Post by **speedbump** » 24 May 2010, 17:34

93 850 GLT, 237k, TX

I have problems getting my AC to work after replacing the ECU (the replacement is identical to the original). I want to use a toggle switch to turn the AC on/off bypassing the ECU. I’d appreciate it if anyone knows how to do this or has wiring diagrams indicating which wires to connect to.

Thanks,
speedbump

Post by **Ozark Lee** » 24 May 2010, 17:48

Are you asking about the ECC or the ECU. The only place the ECU gets involved is after the A/C pressure comes up and the controller detects that the A/C is running. It changes the idle mixture and turns on the engine cooling fan but the A/C clutch is controlled by the ECC via the A/C relay and the low pressure switch.

...Lee

speedbump · Post by **speedbump** » 24 May 2010, 17:55

I’m thinking of bypassing the A/C relay. Can this be done?

Post by **Ozark Lee** » 24 May 2010, 18:01

You can run a wire from the positive battery terminal straight to the A/C clutch and bypass everything - but I wouldn't advise that you do so. A low coolant charge means no circulating oil which generally means a compressor failure and it can happen quickly.

...Lee

speedbump · Post by **speedbump** » 24 May 2010, 18:27

My A/c system was working well before the old ECU fried. Where's the A/C clutch?

Post by **Ozark Lee** » 25 May 2010, 16:16

It is the only wire that goes to the A/C compressor, towards the front of it. Again, I advise against this since it bypasses all of the safeguards that are in place to protect the compressor.

...Lee