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Afternoon all,
I've been tracking down a problem with the cooling fan on my '84 that's been causing it to run all the time, even with the A/C off and the engine cold and not running. The ground side of the fan control relay coil is getting a constant ground, even with the coolant temp sensor and both A/C pressure switches unplugged. I think I found the problem (a wire nut tying a wire near the A/C compressor to ground) but was wondering if someone had an electrical wiring diagram for the A/C system and where the cooling fan relay circuit ties in (I'm assuming the low pressure switch). I have the diagram for the fan relay circuit, but can't find the A/C system.
Thanks,
Reed
That's probably a good idea to verify that the temp sensor works since I just replaced it (old one had broken and was partially melted to a header). I think my current plan is to wire a relay in parallel between the high pressure A/C switch and the compressor, and use the relay to close the ground when the compressor turns on, ensuring the fan comes on when the A/C comes on. It's a more complicated solution, but it restores the full function of the cooling fan.
Thanks,
Reed
I mean wiring an additional relay (the cooling fan relay is working fine) to emulate the A/C switch in the bottom of the attached diagram for the cooling fan.
I mean wiring an additional relay (the cooling fan relay is working fine) to emulate the A/C switch in the bottom of the attached diagram for the cooling fan.
Why do you need an additional relay? Your diagram is correct. You only need one relay. Is there some confusion about the a/c pressure switch in your compressor? It's NOT the "high pressure safety cut-out switch".
The a/c pressure switch is located on the top left (drivers) side of the compressor, and has a "pinch" style connector.
Last edited by Hot Rod Roy; 07-10-2017 at 06:43 PM.
Why do you need an additional relay? Your diagram is correct. You only need one relay. Is there some confusion about the a/c pressure switch in your compressor? It's NOT the "high pressure safety cut-out switch".
The a/c pressure switch is located on the top left (drivers) side of the compressor, and has a "pinch" style connector.
For whatever reason the compressor on this car does not have that switch. My guess is the compressor was replaced at some point with a non-exact match that doesn't have that switch which is why someone tied the wire to ground with a wirenut. I hate having to splice into the good wiring to put in a relay, but short of replacing the compressor (unnecessary and expensive), a relay is the best way I can think of to restore the function. I'm open to suggestions, though.
Thanks,
Reed
Why do you need an additional relay? Your diagram is correct. You only need one relay. Is there some confusion about the a/c pressure switch in your compressor? It's NOT the "high pressure safety cut-out switch".
The a/c pressure switch is located on the top left (drivers) side of the compressor, and has a "pinch" style connector.
Appreciate the photo, it's the first I've seen of the elusive switch. I double-checked my compressor and there appears to be a flat and snap ring, like maybe it has a port for such a switch, but the switch/connection itself is not there. I got the relay wired in this weekend and it seems to be working well. Not the tidiest fix, but it works.
Thanks,
Reed
07-02-2017, 05:00 PM
84 A/C system wiring
