Fixing the AC

I am not getting any voltage down at the AC clutch for it to engage. 2 fuses are ok and I have tested the relay and change it with fan relay I know is working. 0 voltage at red wire to clutch. Also low pressure switch for coolant is closed so non-issue there

Anyone have some ideas please.

What year is the vehicle?


The pressure switch could be seeing low charge and not allow power to be sent to compressor. I figure the ecm is looking for proper pressure before sending power.

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It would help to know the year model. A generic schematic shows the following in regards to the 4 terminals at the compressor clutch relay.

Trigger wire for the relay hot all the time.
Power lead to clutch hot with the key on.
Mate to the power lead powered when the relay is triggered and goes to clutch.
The ground for the trigger wire goes through the PCM which relies on inputs from various things.

A condenser noise filter is also shown in the lead between the relay and clutch. Check for power on both sides of that.
Check that the trigger circuit in the relay is actually making ground through the PCM.