AC Question

[AndrewG]

Not sure if your summer is as hot as here, but I finally got around to looking at a two year old problem of my AC.

Deciding to do this properly, I swapped in a compressor that I know worked when it came out of a Disco I. Brought it up to a friend garage and dis the vacuum, leak test and recharge. Success ! I had beautiful cold air.......for about 10 mins !

On the way home the cold cold air turned into hot air. Checking the compressor, the clutch was not engaging, but the condenser fans were. I traced the wires at the ECU, pin 33, and found 12V for the clutch to engage, I then moved on to the 5 leg relay where I found the 12V again, switched out the relay (just in case) but no clutch or 12V at the clutch connector ! I swapped the relay for the clutch with the relay for the fan (finding that removing the clutch relay turns off the power to the fan !) to make sure that the relays both worked. Still no clutch but the fans worked with the swapped relays.

I started to get intermittent 12V across the two terminals of the clutch connector, but even connecting them to the compressor gave me nothing, and when disconnected again the 12V was gone.

Does anyone know where I can get some details on the circuit and logic ? The Workshop manual is very vague, Haynes is useless and the Wiring diagram is where I found the ECU and relay info. Any ideas ?

[joshua.mcguoirk]

Before you diagnose the electrical gremlins... ensure that the correct amount of refrigerant was added. It may have been over filled. The high-pressure cut out may be preventing the compressor from locking.

What type of refrigerant was added? R134a or R12
Was oil added to the system charge?
What do the high and low pressures read?

You can hook up a manifold and "hot-wire" the compressor to get a reading too. However, you do not want to run the compressor like this long if the pressures are high. This can cause other system failures.

[AndrewG]

Thanks for the reply ! I'm going to have to figure out how to measure the pressure on the high side, I only have a guage for the low side.

The system was is a 134A system and was charged using an automatic system in a garage with the settings for a 1995 RRC 4.2i engine ! So it should have been perfect !