Hi all,
I just can't seem to figure out how the AC compressor clutch and the electric fan are supposed to be wired up. The wiring seems to be a mix between the XJS and XJ6 and I just don't know which diagram to follow. Before I started to mess around with this wiring, the electric fan would always run when the AC control dial was turned from the OFF position and the coolant temperature switch was disconnected. I want the fan to run either when AC is turned on or when the temperature switch closes, without the annoying "bootstrap" circuit that allows it to run only once after engine shutdown.

There is one cut green wire with an orange/brown stripe coming to the AC compressor.


On the other end it leads to the electric fan relay, before that it is connected to a board with a diode. This diode doesn't pass current in either direction, just like the two diodes within the electric fan wiring. I would expect a faulty diode to pass current in both directions rather than none, nevertheless I got new diodes to try and replace them. Is this original "board" recommended to use or can I solder the diode straight to the wires? Both of these diode boards look pretty questionable to me and I'm not sure if putting them back is the right move.


Without the clutch engaged the compressor shaft spins. I got the clutch to engage by connecting one plug to ground and the other straight to 12 V, then the shaft wouldn't spin, which tells me the compressor might still be good. If the compressor proved to be bad, I was thinking I would take the AC system out of the car for now to make working on other things easier. I'd like to wire it up and see what it needs. Is the wire by the compressor supposed to connect to the compressor clutch and the other to ground, and if so, does polarity matter?

Thank you,
Dan
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there is a modification for the XJ-6 SERIES 3 which allows the auxiliary fan to run constantly whenever the a/c compressor runs just like in the XJ-12 SERIES 3.

you will need to tap into one of the red relay wires and add a DIODE to the new wire.

Otherwise, in the XJ-6, the auxiliary fan only runs automatically when the coolant temperature reaches a pre-set temperature triggering the thermal sensor-switch located at the right bottom of the radiator.

if it is not doing that, either the thermal sensor-switch, the red relay, or the fan motor might have failed.

I did the modification to my XJ-6 and there are two issues with it:

1) it is noisy on the outside of the car,
2) you don't want the auxiliary fan running in Winter because you want to use the Heater, so the mod must be disconnected in Fall.

 

That's easy, use mid-80s XJS V12 wiring schematic, up to at least '88. In '89 they started making some changes


Clarify please.

Do you want to eliminate the after-cooling?

Or do want to create a circuit that allows more than one after-cooling cycle?

Cheers
DD

 

Yes, you can

Cheers
DD

 

I should clarify my car IS an XJ12, so this circuitry is already included. That new wire with a diode you're talking about is shown on the second picture. The green/white wire leaving the diode on the lower side leads to the red relay.

More than one cooling cycle, as per the description on page 228 in Kirby's book. Don't care about noise so much as keeping the engine cool.

I'll try to wire it up according to the schematic you recommend Doug. Any suggestions with the compressor clutch though?

Thanks!