2004 Silverado AC Clutch not engaging.

[Dkirk86]

I have a 2004 Silverado and the AC clutch wont engage.  I have jumped the low pressure switch.  I am getting 4.8 volts on the blue wire for the low pressure switch connector and ground on the black wire.  I get 5 volts on the gray wire for the high pressure switch and ground on the black wire.  I have swapped the AC relay with a good working relay with no luck.

 

The clutch will only engage if I jump pins 30 and 87 for the AC relay.

 

I am not sure what to test next.  Any Ideas?

[sefiroxx]

Have you checked pressure in the system with full guages?

The computer sends 5v reference signals to the pressure swItches. The return signal will be 0-5 depending on actual pressure. If results come back above a certain level, the computer will ground the the relay. You have bypassed the pressure safety control loop.

You can jumper the pressure swItches, sending 5v back to the computer. Do the low one first, then high. If system works, then a switch is bad or the system is actually low or high. Which gets you back to. . .

Have you checked pressure in the system?