Recently I noticed that the a/c compressor is not engaging- if I jump the compressor relay, clutch will engage, but no condenser fan. Both clutch relay and condenser fan relay (through the diode block)are activated by the green/brown wire from the Delanaire control unit. Blowers and modes seems to function normally. The 15A fuse in the main left fuse panel and the in line fuse for the compressor clutch are good.

First question- the wiring diagram shows an in line 3A fuse as part of the Delanaire unit harness- I assume it is under the ski slope, as it is powered by CP7, which shows in that location.

Second question- if that 3A fuse blows, does the entire system stop or is it by chance just a protection for the clutch relay circuit?

 

Answered my own question. The circuit through that 3A fuse is the only power feed, so nothing would work if it’s blown. Also, the Delanaire III diagnostic manual basically says that whenever the system is on, there should be power on pin 20, which turns on the a/c clutch relay, and through the diode the condenser fan relay.
So unless there is something going on with the evaporator temperature sensor, the ECM is bad. I have a spare…

 

New (well used) Delanaire ECM fixed it.