ps374

The Z51 performance package on early C4's had two fans. One in front of the radiator and the stock one on the fan shroud. Are both fans suppose to go on at the same time and does the switch in the head control both?

WVZR-1

They weren't meant to operate at the same time and had a separate switch. They "could be" wired to your '84 (which didn't have) to operate from the same switch/relay combination. I believe I recall some doing it this way and others actually adding the complete functionality of the AUX.

*****

I might have mistaken you for another "upstate NY'er". What year is your car?

I answered my own question, your car is the '84 that I thought it was.

Cliff Harris

The fan behind the radiator is controlled by the ECM, based on the coolant temperature measured on the front of the intake manifold.

The auxiliary fan in front of the A/C condenser is controlled by a coolant temperature switch between spark plugs #6 and #8 on 1984 cars (I believe that is also true for 1985 as well). In 1986 the auxiliary fan coolant switch was moved to the driver's side.

WVZR-1

I don't believe that's so for an '84 which didn't have the AUX option. I believe the fan was controlled by a switch in the rear of the RH cylinder head. There's no ECM control for the L83 cars.

ps374

I believe this is correct that the cooling fan does not use the ECM on the 84. My FSM on page 8A-149 says the switch turns the fan on. I have never seen my front fan ever go on so I don't know what its there for. I however am worried about letting my engine get up to 238 before the fan comes on.The last owner has my fan running all the time since this was a Florida car. I disconnected the AC switch he jumped so that the fan always runs planning for the colder months but I did not see the fan go on and turned the car off when I saw the temp go to 230. Isn't this a little to hot to run the engine? My engine never runs that hot.

WVZR-1

So a PO added the AUX fan to your '84 and used the AC switch as a trigger/control device OR so it seems you believe? The 230 number you mention seems certainly excessive for your car. There's a combination that the PO used to control the fans and you might compare maybe the wiring to a later Z51 or AUX equipped car. When you undid the AC jumper (you called it) you broke the entire control path for both of the fans it seems.

I believe you need to trace the wiring and compare what's there to what's in tour FSM and I'd think there's no or few similarities.

I'd look for maybe a second relay controlling the AUX fan and maybe when you removed the "jumper" you've defeated the trigger/control.

ps374

Am I understanding you correctly in that the AC connector must be connected for the fan to come on without the AC on when switch reaches temps over 200 ? If so, that would explain why the switch is not working when I disconnect the AC plug on top of the compressor.

WVZR-1

I'm only guessing but the PO added the "pusher" so it would be very dependent upon how the PO did it. I doubt that if it was wired to the AC it was temperature controlled so you would need to do something to command it on when desired. Maybe just letting the current switch command both fans to ON when the temp requires it. That would seem the easiest.

Cliff Harris

I made a bad assumption and guessed it wasn't an '84. All three statements are true for an '84.

JrRifleCoach

FWIW.
I added the pusher fan to my 86.
In a nutshell that fan has no cooling value what-so-ever.
Connected with a manual switch I've witnessed temps climb to 229 with that fan on in traffic.
Then switched the fan off and watched temps drop to 215.
Conditions; A/C off, OAT 97*, Half a car length between cars, DeWitts radiator.
This is only one example of many instances I've tested.

If you need one I'll sell the fan/brackets for $50 + shipping
PM me.

ex-x-fire

I bet the extra fan helps the a/c stay cool. I had my 84 in a hot Chicago traffic jam, though the engine didn't over heat, the a/c started to blow warm air. Once we got up to speed the a/c started to blow cold air again. Mine is an early 84 with z-51 but no extra fan or oil cooler.

WVZR-1

I've always maintained that it was the primary function of every fan that GM has used as a "pusher" except those that are isolated in an area where they actually only blow through a cooler like the trans or engine oil. I've generally been met with disagreement so I don't even bother discussing it any longer. I used the argument that even the "puller" fans on the F-body cars only got the 2D fan if it was an AC equipped car.