Mine situation may be different from yours. Mine had no action at all. It looks like that electricity never get to the compressor. The power supply (12V) to the compressor is control from the MCC or ECC front panel circuit. When I turn on the AC button on the MCC front panel, blue LED comes on and the AC relay behind the glove box receives power from the MCC front panel circuitry. 12V power will pass through the AC relay and get to the Lower Pressure switch on the AC line next to the firewall. That switch should be at ON state if the system is fully charged. This allows electricity passing through to get to the thermoswitch of the compressor. If the compressor's temperature is below 100F (not sure the exact value), this thermoswitch should let electricity going into the compressor and AC should be on.

When you short the connector of the Lower Pressure switch, you bypass the switch to provide the electricity to the compressor directly. If compressor comes on, that means either the R134 is lower in the system or Lower pressure switch is bad. I assume the thermoswitch on the compressor is ok. I should have checked whether there is a 12V at the Lower Pressure switch connector to make sure the AC relay is working fine. If AC relay is at OPEN position, then there will be no 12V at the Lower Pressure switch connector. Hence no power to the compressor.

I am not sure the actual wiring of the ECC system. I would think that it is quite similar since mine is MCC system.

Hope this help.

Ching-Ho Cheng
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1995 855 NA, Bilstein Strut & Shocks, Volvo Protective Grill, K&N Filter, E-Code Lens, ClearCorner Light, Alpine CD-Changer, AutoDim RearView Mirror, 6000K HID