Automotive Air Conditioning Information Forum (Archives)
compressor wiring questions
joemanND on 
Tue March 13, 2012 2:24 PM 
I have a new compressor, a four seasons 77314 which is really just a reman Nippondenso. It's replacing a compressor in an old 89 corolla, but the wiring in the car is a little suspect, so I wanted to make sure I understand what the wiring on the compressor is for.
There's a connector on top of the compressor and the contact have electrical continuity, so I think this is the high pressure cut off switch, right?
There's two wires coming out of the end opposite of the pulley. They're opposite the suction port, so this is the low pressure cut off switch, right? It reads about 240 Ohms... I suspect that'll go towards zero once the system is pressurized?
And there's also the clutch connector... that's pretty obvious.
Lastly, the low pressure switch, high pressure switch, and clutch relay coil should be wired in series so that pressure that's too high/low releases the clutch, right?
Thanks for the help!
here's a link to the best picture on the net of the compressor that i could find. The new compressor didn't come with the 4-wire connector shown in the top left of the picture.
http://images.wrenchead.com/smartpages/partinfo_resize/FSE/77314.jpg
mk378 on Tue March 13, 2012 3:36 PM
Japanese cars were usually fitted with a combo high / low pressure switch in a high side line somewhere. The sensor in the back of the compressor is a rpm sensor which feeds the "A/C Amplifier". The one on top is likely a thermal switch.
joemanND on Tue March 13, 2012 3:52 PM
oh, interesting! Any part number ideas or aftermarket add-on options for that combo high/low pressure switch? I must be missing some parts.
robs on Tue March 13, 2012 6:20 PM 
I believe THIS SWITCH is what you are after. Its a standard binary switch. Let us know if there is anything else.
mk378 on Wed March 14, 2012 10:12 PM
On the picture, that's definitely an rpm sensor in the side. It's a reluctance type that generates AC as the compressor rotates. And it's a temperature switch on top-- normally closed, opens if the compressor overheats.
The pressure switch was often in a port on the receiver-drier. Look for wires near the drier that don't go anywhere.
Edited: Wed March 14, 2012 at 10:18 PM by mk378
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