1G Would a disconnected A/C engine coolant temp switch cause the A/C to not work?

[XC92]

For the past several years the A/C on my '92 Talon TSi hasn't put out cold air. Prior to this it worked great, for around 30 years. I've had to do a bunch of unrelated work on the car and some other cars so I haven't had the time to get to it.

But today I noticed that the A/C engine coolant temp switch, the one furthest up and to the passenger side by the thermostat, had one of its wires broken. It may have been this way for some time. So the switch isn't sending the ECU a signal.

Could this cause the A/C to not put out cold air? I mean none, as opposed to somewhat cold air as on a dying A/C. It's not an urgent issue as it's late fall and too cold to need A/C (although sometimes it helps remove condensation in winter if run for a few minutes), but I'm curious.

I patched the wire but didn't start the car to test it as I've been doing work on the car and the battery's still out. I should be done tomorrow so I'll check to see if this fixed the A/C.

 

[dwb]

Yes but that would be too easy

 

[XC92]

Yes but that would be too easy

I like easy, especially after all the work I've done on 3 cars over the past few years!

But seriously, this could actually be why the A/C stopped working? I mean it didn't slowly die, making warmer and warmer air until it was basically another heater. One day it was working, then one day it wasn't.

 

[dwb]

Possibly but you gotta test it. Listen for the compressor to kick on when you push the button. Go from there.

 

[XC92]

Possibly but you gotta test it. Listen for the compressor to kick on when you push the button. Go from there.

Honestly I'm not sure what to listen for. Typical "the a/c just came on" sound, similar to a home window unit or fridge?

 

[dwb]

Just listen for it to click as soon as the button is pushed. Have a friend help so you can be near the compressor. You should also notice the fans and change in RPM.

 

[XC92]

Just listen for it to click as soon as the button is pushed. Have a friend help so you can be near the compressor. You should also notice the fans and change in RPM.

What if I have no friends?

 

[CrackedDSM]

That switch disables the compressor if coolant goes over a certain degree. So yeah. 100% could be the problem.

 

[XC92]

That switch disables the compressor if coolant goes over a certain degree. So yeah. 100% could be the problem.

So it's normally "off" and the broken wire makes it look "on"?

 

[CrackedDSM]

So it's normally "off" and the broken wire makes it look "on"?

That I do not know. I was hoping @steve or one of the other DSM electronic gurus could chime in here.

 

[XC92]

That I do not know. I was hoping @steve or one of the other DSM electronic gurus could chime in here.

Doesn't really matter, it does what it does, I was just curious.

 

[pauleyman]

For the past several years the A/C on my '92 Talon TSi hasn't put out cold air. Prior to this it worked great, for around 30 years. I've had to do a bunch of unrelated work on the car and some other cars so I haven't had the time to get to it.

But today I noticed that the A/C engine coolant temp switch, the one furthest up and to the passenger side by the thermostat, had one of its wires broken. It may have been this way for some time. So the switch isn't sending the ECU a signal.

Could this cause the A/C to not put out cold air?

yup. Compressor won't come on without that

I mean none, as opposed to somewhat cold air as on a dying A/C. It's not an urgent issue as it's late fall and too cold to need A/C (although sometimes it helps remove condensation in winter if run for a few minutes), but I'm curious.

I patched the wire but didn't start the car to test it as I've been doing work on the car and the battery's still out. I should be done tomorrow so I'll check to see if this fixed the A/C.

 

[XC92]

yup. Compressor won't come on without that

Damn, if this was why, I feel like an idiot. 2 summers w/o a/c. Granted, I didn't do much driving with the car, but still. The a/c on this car is really powerful.

Similar thing happened to my mom's Camry recently, but worse. The ECU coolant sensor wire broke and the engine had major misfires. Patched the wire, no misfires.

 

[DSMPT]

Without the A/C coolant temp switch connected, I think it would require to ground to trigger the clutch relay or bypass the switch to engage the compressor. That's what I had to do when I installed the A/C components on my 1g without the A/C coolant temp switch.