vtraudt

AC clutch not kicking in.
First, used kit to charge system, thinking low.
No change.
Later bought better gauge set with high and low pressure side gauge.
Clutch works when +12V is hooked up to clutch.
Even with clutch 'manually' engaged not blowing cold.

Pressures without clutch running:
- low 90+ psi ("danger" color on gauge)
- high 150 psi ("charged")

Pressures with clutch running:
- low 40 psi ("charged")
- high 300 psi

What does this behavior 'mean'?

I found the connector on the passenger side of the condensor.
Is that the low pressure switch?

It has 4 wires (only used to see 2 wires for normal low pressure switch). Is it maybe a high and low pressure switch combined?
Does someone has a pin out for this connector?

I would like to try bypassing the switch?

a) what is causing the clutch NOT to engage?
b) is the switch bad?
c) how can I test the switch?
d) if the switch on the condensor is NOT the low and high pressure switch, where are those switches located then?

turbo510

Which of your cars is this? I'm surprised that you would see two different pressures with the AC clutch not engaged. Pressures should be the same. And if you hotwire the clutch so it runs, get the pressures that you listed, you should be getting AC action. You said that it didn't blow cold: if you feel the large "return" pipe next to the battery, is it cold? If so, then maybe one of your problem is with the blend flaps under the dash.

vtraudt

This is on the 1998 A4 AEB.
The pressure should be different. When the pump/clutch is not on, nothing keeps the 'high' side pressurized. Can someone confirm what the pressures (high/low) should read with compressor running and compressor off?

I will go out and check the temp on the high and low line. The high (IIRC) SHOULD be hot.

Regarding the switch:
a) pin out for the 4 wire on the passenger side of condenser?
b) is that the high or low pressure switch?
c) is there another switch?
d) can something 'block' the flow of coolant? Or is it basically a closed loop system without valves?