AC questions
 

2001 Sport 4.0, ac compressor not engaging. Low pressure valve reads 60 with oil and refrigerant plenty.

I tried the shim trick. Had two shims. Took one out, no luck. Took both out, no luck.

Tried jumping the low pressure switch connector, no luck.

I believe this must mean that i have an electrical issue?

I swapped out fuse and relay, no luck.

Could my electrical issue just be a bad compressor? How else can i test?

Here's some data pertaining to the 2000/2001 AC system.


Note that there is a Dual Function High Pressure Switch in the circuit as well as the Low Pressure Switch.


Attachment 309910


Attachment 309911

This is a great picture. I was going to suggest the high pressure switch also. If you have gauges then you can jump the switch to see if the clutch engages. The clutch itself may also be bad, so a test light to see if power is getting to the clutch would be good too.

Here's a pin out of the High Pressure Switch connector.


You can jump pin cavities 1 to 3 to test the clutch.


Attachment 309903

Thank you. I am thinking my next test should be to hotwire straight to the compressor. If it does not come on, it is bad?

Why?


Test to see if you have 12 volts at the compressor clutch connector after you've jumped the switches.

I jumped the high pressure switch pin 1 and 3. The compressor did not come on. I was able to jump pin 2 and 4 and turn the electric fan on.

What does this mean?

Do i need to jump the low pressure switch and the high pressure switch at the same time in case they are both out?

Give this a try. With both switches jumped, and if the compressor still won't engage remove the compressor clutch connector and see if there is battery voltage at the connector.

I jumped both switches at the same time. I unhooked the compressor connector. Using a test light, it does not appear to have 12 volts at the connector.

How do I trace that down?


Also, when i jump either switch, or turn the ac on with the switches connected, the engine does adjust throttle as if the ac compressor is activated. Only, the compressor is not activated.

I tried testing again with volt meter. I tested with all connections connected. No power at the compressor connector. I tested with switches jumped. No power.

Next, I ran a hotwire from the positive battery cable to the compressor connector. The compressor worked fine, clutch engaged, cold air.

How to trace back electrical?