Is it safe to assume that an open circuit across the receiver/drier leads indicates a low pressure condition that will prevent compressor operation? Suddenly no AC today. Tried the defrost and still got hot air. Have already fitted a separate relay in the line to the compressor, so pretty sure the control board relay is still OK. Been a while since AC was used, but very few miles on a refurbed compressor and regas. No apparent fuse involved in the AC anywhere?
jp 83 Euro S AT 57k

 

Yeah, the system doesn't have a fuse. You can add one fairly easily in line with the freeze switch though! By design the relay in the head unit is the fuse unfortunately.

If the low pressure switch is open then yes, it will not allow the compressor to activate as that is part of the current path. It basically goes from the head unit to the freeze switch to the low pressure switch and ultimately the compressor.

 

Thanks. I guess the 'freeze' switch is on the evaporator somewhere , and also is open when there is a problem? With a separate relay firing the compressor clutch, what sort of fuse rating should I put in front of the freeze switch? Where should such a fuse fit in - I see a connection at J2 going to Q2 then to the receiver/drier switch. Easiest to fit it at the switch, input at terminal 1?
Off to see about getting the system checked soon, but probably wont find anybody until sometime into January.
jp 83 Euro S AT 57k

 

You can momentarily jump these switches also...that irules out the control head and relays. Odds are it’s low on charge.

 

I used a 5 amp fuse as it is easy to find. It is a 2 amp circuit so a 3 amp fuse would be perfect if you can get one.

I also installed a second relay that directly powers the compressor clutch to take all the load off of the head unit. So I installed a 1 amp fuse in place of the 5 amp.

 

Thanks. As soon the heat dies down (44C, 111F today) I will fit a 5A in front of the freeze switch. Already have a separate relay in the compressor clutch circuit. Then find somebody to regas it!
thanks
jp 83 Euro S AT 57k