AC Compressor is not engaging

[RockRobster]

Not sure what the deal is with the AC compressor.  It is simply not engaging. 

 

I have checked the AC fuse, the fusible links, and looked for loose or frayed wires.  No results there.

 

So, the question is, what makes the compressor engage?  It looks like there is a two conductor wire harness, going through a connector, that connects to the sensor at the front of the compressor.  Does the signal to engage compressor come through this connection?

 

What else am I missing?

 

My determination to fix at this time of year is driven by the de-humidifying function of the unit, not the cold air function.  Very moist air out here in the Pac NW.

 

Thanks in advance.

[Gloyale]

The compressor will not engage for a few reasons.

 

#1  Low pressure in the system.  If there isn't enough pressure, the switch by the dryer will not pass power through to the circuit that drives the clutch.  Test for 12v on the BY wire into the switch(no volts = problem with microswitch under dash) and 12v on the RW wire out of switch(no volts = pressure too low)

 

#2  Sensor on the front of the pulley out of place, disconnected.  This sensor must make a magnetic pulse, that pulse is seen by the pulser/relay mounted up behind the glove box and in turn the relay engages clutch.  If the sensor doesn't pulse, then the relay won't close the clutch circuit.  Not sure how to test.

 

#3  Thermoswitch in the evaporator closes grounding circuit of the pulser relay.  test RB wire at the pulser for continuity to ground...disconnected from pulser.

 

#4  Compressor clutch itself failed.  Jumper 12v to clutch to manually check if it engages.

[MR_Loyale]

What GLoyale said.

 

+1

 

Also Haynes book has step by step with pictures on this.

Edited October 1, 2013 by MR_Loyale

[RockRobster]

Guys,

 

Thanks for the answers, I will get the Haynes book and scope it out.