Toyota Repair: 1994 Toyota Carina A/C problem, electronic leak detector, toyota carina

Question
Hello Ted,
I've bought a 1994 Carina (GLi 2.0) in mint condition, except for the A/C which doesn't work, i.e. the electro-magnetic switch on the compressor isn't activated by pushing the A/C switch on the dash. I have checked the 50amp fuse under the hood, it's OK. But I'm wondering whether this fuse is the only one for the A/C system, because when I take out this fuse, the relay connected to the A/C pump is still under current when I turn on ignition.
(I have a wiring diagram for this A/C system, but it's too complicated for a layman like me....)
Thanks a lot for your help!
Otto Schmidt, Amsterdam, The Netherlands


Answer
Hello Otto, the main reason for the A/C compressor clutch to not engage is that the freon pressure in the system is too low and in most cases this is because there is a leak in the system, if there is not enough freon pressure the compressor will not engage because there is a pressure sensing switch in the high pressure side, this function is built in to avoid damage to the compressor.
The first step is to try to add some freon to the system and see if the compressor starts up, if so, the second step is to find out where the original freon went, probably a leak, the leak can be found either by introducing a flouro-dye in to the system or with an electronic leak detector, in either case I recommend finding a shop that can diagnose the problem, the second choice is to get a refill kit from an autoparts store and servicing the system yourself by adding some refrigerant, follow the instructions, see how long it lasts, eventually it will leak out again it depends how big the leak is.