Trying to help my friend Hal with AC on his '94 XJS. Key on, AC switch off, system cycles the fan blower and compressor clutch on and off continuously, will not stop until ignition is turned off. However, system functions normally when turned on, both heat and AC. Prior to this, system worked fine. Any ideas/advice much appreciated.

Thanks,

Craig

 

If you can locate the pressure switch, low I think, unplug the switch and see if it still does it. Otherwise something is activating the clutch relay. Here is the schematic which may be easier to see. In the end, the clutch coil needs power to pull or activate it so either the relay is being activated without control or power is passing through the relay when it shouldn't