Hi. I have a 1986 Iroc that now has a 350 TPI with SD. I am still using the single fan for now and I also did delete the AC. As soon as you turn on the ignition the fan comes on full blast. I was thinking that when I deleted the AC I may have accidentally taken off the ground that turns on the AC so itis on all the time. Anyone know where the fan gets its signal from the AC to turn on the fan(which wire to relay) or any ideas why the fan will not turn off.

Thank YOu

Chris

 

I don't know if it would be the same color for you but, I had a similar problem on my '87 when I started getting it back together.

On my car, the A/C pressure switch wasn't installed yet (along with the line it was attached to) so the blue wire the ran to it from the ECM had to be grounded to make the fan stop running (or work properly I suppose). On the '88 GTA harness I'm using on my bud's truck, the A/C press switch wire is grey, other wire is black (goes to gnd).
As you can see here..

http://92b4crs.tripod.com/86wiring/dia-pics/63-7.jpg
(drag & drop this link up to your browser addy bar to view)

... it shows light blue & green.... pick your fav. color & go with that I guess... . Apparently the colors do vary over the years. The link above is for '86 F code though..

 

My fan motor is grounded directly to the frame, so the relay must only provide 12 volts. In the relay I have a green with a white stripe, orange(power all the time), black with a red stripe(to fan motor), and one more, I think is red that has power all the time. I cut the green with a white stripe and the fan cut off, but since the motor is not ready to run very long I could not run the car and get it to operating temps. When I ground the green with white stripe wire the fan cut back on, leading me to believe it is already grounded in the harness somewhere else. Why does both the orange and red wires have power is one of these the one that needs to be grounded? Also how can I test the fan with the key on, but motor not running. Wouldnt putting the computer in diagnostic mode turn on the fan or ground both sides of the temp switch? Sorry so long and thanks

Chris

 

The green/white wire is a controlled ground by the ECM. If the A/C press. switch is not hooked up/the wire that would normally be hooked to the ECM is not grounded, the ECM is seeing that the A/C switch is open and the A/C is 'on', thus makeing the ECM call for the fan to be on.



If the switch/ A/C system is no longer present, the wire the led to that A/C press. switch must be grounded as the A/C switch is closed (complete circuit to ground) when the A/C is not on. Upon X amount od A/C line pressure, the switch opens (disconnecting the ground) and signals the ECM to kick the fan on. All of this though, is merely signaling for the ECM to ground the green/white wire to the relay to kick the fan on.

Thru the years, the system changes here & there but the basic principal is the same.

If you question my sanity (as I often do ), I am currently doing a TPI/interior harness swap in my friends '72 chevy truck that is about to make me lose what little sanity/grey matter I have left

 

You cut the green w/white strip and the fan turned off. There's your answer, the ECM has a valid fan request and is supplying the ground to trigger the relay.
The other smaller wire you mentioned at the relay as "red" is ignition power to te relay coil. The ground from the ECM trips the relay and the fan runs.
http://www.eecis.udel.edu/~davis/z28...730v8tpi-4.jpg

Did you check the stupid things like the lever above the radio? If it's in A/C then the fan will run as long as the key is on whether the car is running or not.

Other then that you need to find out what is asking for A/C like mentioned in the above post.

Seem to be missing some information about the cars status if you are saying it's not ready to run a long time. What's not together yet or connected?

 

Sorry to resurrect an old post, BUT I am ready to attack this problem again and can still not figure out why green wire is always grounded. Snap On and Tunercats is both saying that the fan request is no. Could it be something that happened between the single fan/no fan switch Maf system to the dual fan/SD system that got messed up. Also I can not find any AC wire that should be grounded that would make the fan stop.


Thanks Again everyone


Chris