I have dual electric fans on my 87 iroc 305tbi, As soon as i turn the key on they come on and won't shut off. i found the fan control sensor in the passenger side. the previous owner plugged it. i grounded the wire and the passenger side stays on constantly with the drivers side. Any suggestions to what could be causing this?

 

the switch to turn them on prolly went bad and the previous owner just wired them to come on when the key is on. thats what i did.

 

On both the my 90 RS & 92 RS, I had spliced in an extra wire on the firewall relay, to ground out & run the fan key on=fan on.

During the summer I'd ground that wire. During the winter (if i remembered) I'd disconnect that extra wire & they'd turn on & off like stock, controlled by the sensor.

 

For starts,TBI wasn't dual fan so, it's either not the original fans or, motor.

Second, the single fan for TBI was only run by the fan switch in the passenger head or by the A/C (238°F on temp).

An 87 dual fan setup (TPI) would have the ECM - A/C controlling the primary fan (220°F) and the secondary would run only by the fan switch (238°F).

As a guess, you may have a swapped in dual fan setup rigged to just run.