Rep Power: 0

I'm working my way through some ac troubleshooting flow charts in the service manual. At the point where it says to check the voltage between the number on terminal of the AC pressure switch connector and ground it says to see if you get "battery voltage". Battery voltage would be about 12-14 volts. I measured five volts.

Elsewhere I have heard that these wires are coming from the ECM. If that is the case I would expect to see five volts.

What voltage am I supposed to see here?

Thanks

 
Rep Power: 517

Whenever you make a thread like this, please post your vehicle info.... model, trim, year, # of doors, trans type, etc. Makes it easier to look up info.

On a 97 the AC pressure switch is part of the AC request signal circuit to the PCM, (according to the wiring diagram I have here) so I would expect to see 5v (or ground if the system is trying to operate).

Request path:
HVAC control panel --> AC thermostat --> underhood fusebox (fan relays) --> Pressure switch --> PCM

The PCM sends a 5V, and the "AC request" is (typically) a ground, which originates within the HVAC panel.

When the PCM detects its 5v has been grounded, it turns on the clutch relay.

HTH