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Old 07-04-2020   #11
Corvette95
 
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Default Re: Fans on when ignition in accessory position

Didn't see the part where you asked if the a/c has to be in run for the pressure switch to run the fan....yes.
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Old 07-04-2020   #12
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Default Re: Fans on when ignition in accessory position

this is a stock 92 prom. Yes Tech one flashes 12, car runs, etc
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Old 07-04-2020   #13
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Default Re: Fans on when ignition in accessory position

Other than sticking relay, I think they have power from fusible links at all times even with key off, an aftermarket fan switch, or a fault in ignition switch. Has any wiring work been done under the drivers dash such as Vats bypass, alarm, remote door fob etc?
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1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD
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1989 C4 Conv Wht/Red Auto SOLD
1996 C4 Conv Black/Tan Auto SOLD
1994 C4 Coupe Wht/Blk SOLD
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Old 07-04-2020   #14
LGAFF
 
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Default Re: Fans on when ignition in accessory position

Nope all stock wiring... and its only fan 1
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Old 07-06-2020   #15
Macroblock
 
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Default Re: Fans on when ignition in accessory position

I'm thinking the primary cooling fan is "controlled by the ECM" thru the Green Connector "C6". This provides a (-) signal to th Primary Fan Relay.

If you disconnect the Green Connector and turn the key to "ON", you can verify if the fan is being activated by the ECM or something else. If it runs with the Green Connector removed, it's not the ECM.
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Old 07-06-2020   #16
LGAFF
 
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Default Re: Fans on when ignition in accessory position

I unplugged red and it stopped. Will check green too


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Old 07-06-2020   #17
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Default Re: Fans on when ignition in accessory position

I am able to command the fan off with a Tech 1, which I thought was odd...
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Old 07-07-2020   #18
Macroblock
 
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Default Primary Fan Runs When ignition in "ON" position

Quote:
Originally Posted by LGAFF View Post
I am able to command the fan off with a Tech 1, which I thought was odd...
That's a good sign. It suggests to me the ECM is capable of controlling its (-) output to the primary fan relay on circuit 409, pin 6 of Green Connector (C6).

Could it be you have a Code 14, 15, 52 or 62 set?

If you have any scan-tool (or any device) connected to the ALDL the fan or fans might come on.

If you have a faulty Heater/ AC Controller.

One or several of these inputs to the ECM could be providing false information causing the ECM to activate the primary fan relay:

AC Request (C2),
AC Fan Request (C8),
Coolant Temp. Sensor (B9),
Engine Oil Temp Sensor (B18),
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