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Hi guys, since I’ m restoring the original wiring in my car I noticed this wire, which is the D12 coming from the ECM. Where do I solder it to? I guess there’s another cut blue wire somewhere... the ECM is 1227730, auto trans, 3.1 V6 Lh0. Here’s a pic, thanks in advance!
Goes to the A/C pressure switch. Leaving it open like that should have the cooling fan running whenever the engine is running.
RBob.
Actually, wire 731 gry (ECM BD12) goes to pin F of the secondary fan relay (relay coil), by grounding that wire, the secondary fan will run all the time.
If that was was not connected (open circut) the secondary fan would not run - at least that is what it looks like to me....
It was grounded with the strap on the firewall. Can’t believe how much this car is messed up with the wiring harness...
I guess the A/C system is gone or doesn't work? By grounding that wire to the firewall, this prevents the ECM from running the fan thinking the A/C system is being used (high pressure). Note that on factory delete A/C cars ('90 - '92 MPFI), GM did the same thing.
Tuned, that diagram is for $8D, this is the one for $88:
RBob.
Well then......grounding wire 732 dk blue that goes to the ECM BD12 will bypass the A/C fan press switch (which I assume was done because of a
faulty A/C press switch stuck in the open position)
I guess the A/C system is gone or doesn't work? By grounding that wire to the firewall, this prevents the ECM from running the fan thinking the A/C system is being used (high pressure). Note that on factory delete A/C cars ('90 - '92 MPFI), GM did the same thing.
RBob.
The system never worked properly since I bought the car, the engine went rough and occasionally stalled when the A/C was on. Over time I tried to turn the A/C on occasionally, but the clutch never started again. So I noticed this wire when trying to restore the original wiring...
Thank you all guys, now it' s much more clearer to me! Where' s exactly located the A/C fan pressure switch? I guess the only thing I have to do is to connect that wire to it…
Ok, I’ m trying to find the other side of the wire but I can’t find it... I checked the continuity between the pressure switch and it’s cut wire, it’s okay. Now, which is the path to follow to find the other wire? I’m attaching two pics to let you see a little better.
...."I checked the continuity between the pressure switch and it’s cut wire, it’s okay"......
That is meaningless.....not sure where you are going with that troubleshooting....
The wire in question runs from the pressure switch terminal B to BD12 at the ECM - if a wire is connected
to the pressure switch terminal B and cut before it reaches the ECM splice in a new wire and run it to the ECM - it's that simple
That’s the point, B and D12 are connected regularly, but there’s a junction that was grounded with the strap on the firewall. Is that the original wiring? If so, I’ ll stop to hunt ghosts in my hood!
