Damn fine question. However, I think the answer is more evident when viewing the full diagram; you see that the circuit for the radiator fan (where it branches off into A/C, PGM-FI ECU) continues on through a diode network, branches off again to go to the ECU, and the other path at that second branch goes through the A/C pressure switch, the A/C thermostat, the actual A/C on/off switch on the dash and then through the blower motor fan switch. So, on the one hand, you don’t want the amount of current necessary to power a fan going through all those switches and shit but the more importantly, you don’t want that amount of current flowing into the ECU. The ECU basically watches that circuit to see if there is ground there (in which case it triggers the A/C compressor clutch relay to kick on the A/C) or if there is battery voltage there (which means the circuit doesn’t have a path to ground and so the A/C compressor clutch relay should not be on). The little sensor in the ECU that measures for that battery voltage is probably pretty sensitive and really doesn’t want a ton of current flowing through it. Plus, if there were a problem in that circuit within the ECU, if there was a lot of current there, it could go on to fry a lot of shit. If there is only a little bit of current, then maybe the surrounding circuits will still be OK and you can still drive your car…
Does that make sense? If you have a manual, you can kind of follow what I’m saying a little better with the diagram on page 22-4 in the A/C section.
haha. yea i think it’s time to trade up from the haynes. thanks for the clarification. as always, much appreciated
to the op; try back probing the connector with it plugged into the switch.
if that checks out, maybe test resistance at the sending unit. first cold, then hot
Its the top one that controls the fans.
there’s another temp sensor that’s for your gauge on the dash that is next to the distributor.
the cooling fan realy is behind the left side headlight in fount the battery.
[QUOTE=Daintegra;2202536]Its the top one that controls the fans.
there’s another temp sensor that’s for your gauge on the dash that is next to the distributor.
the cooling fan realy is behind the left side headlight in fount the battery.[/QUOTE]
Thanks for answering that.
One more thing, so whats happening to your fans. I want to know with the AC off, does your fans come on now when reached the specified temperature? And will the fans come on when you shut off the car?
