I have been trying to figure out why the A/C doesn't work properly on our newly acquired 240. So far I have determined with a pressure gauge that the freon was a little low and I added enough to get the low side running pressure to around 40 PSI.

The problem now is that the compressor cycles on and off rapidly. I tried bypassing the low side pressure switch as some suggested and that made no difference.

Then I used a sharp probe to check voltage on the compressor clutch wire at the white plastic connector under the intake manifold. Voltage is ~13 volts when the compressor is engaged, but drops to zero when the compressor disengages. So, I conclude that something upstream from that point is cycling on and off. Unfortunately the Bentley manual is no help at all on this.

I deduce that there must be sensors, switches, logic and one or more relays which determine when the clutch engage line is powered or not. Can anyone help point me in the correct direction? Is this a likely relay problem? Is there a circuit breaker in this line somewhere?

TIA for any help!

John