A/C Problem
 

1988 420 sel. A/C compressor won't run. Fuse is ok. Where is relay located? Does this relay also control the auxillary fan?

If the charge is low, the low pressure sensor will prevent the compressor from kicking in.

Put gauges on the system and check pressure. If pressure is up, turn compressor by hand to make sure it is not locked up and then jump clutch to see if it will come on.

Good luck,