Aux fan
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Always include the year vette you are asking help for as all C4's are not made exactly the same!
The auxilliary fan (the one in front of the radiator) on my 87 is operated
by a thermostatic switch on the left head and the a/c has nothing to do with its operation. I don't know if it is the same for your 89.
The auxilliary fan (the one in front of the radiator) on my 87 is operated
by a thermostatic switch on the left head and the a/c has nothing to do with its operation. I don't know if it is the same for your 89.
Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
fan
the main fan is controlled by the computer. The aux fan is controlled by the fan temp switch.
The main fan in my car shuts off after it goes 35 mph, sooooo,
I tied the aux fan relay coil positive wire to the main fan positive wire.
when the big fan comes on, the little fan comes on too.
The aux fan relay ground is the temp switch in the cylinder head.
I have a switch that I can turn off the little fan by removing the ground from the temp switch to the relay, so in the winter, it doesn't cool off so fast.
If you do it my way, your dash lights dim and then get brighter as the fan comes back on and turns off again.
You can also flip to the volts readout, and watch the volts fluctuate too
The main fan in my car shuts off after it goes 35 mph, sooooo,
I tied the aux fan relay coil positive wire to the main fan positive wire.
when the big fan comes on, the little fan comes on too.
The aux fan relay ground is the temp switch in the cylinder head.
I have a switch that I can turn off the little fan by removing the ground from the temp switch to the relay, so in the winter, it doesn't cool off so fast.
If you do it my way, your dash lights dim and then get brighter as the fan comes back on and turns off again.
You can also flip to the volts readout, and watch the volts fluctuate too
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
fan
if your fan is running all the time, check either the temp switch by pullling the wire off it,
1. if the fan keeps running, the relay is no good
2. if the fan stops, the temp switch is no good
1. if the fan keeps running, the relay is no good
2. if the fan stops, the temp switch is no good
Race Director
Joined: Jun 2004
Posts: 13,949
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From: WI
If you disconnect the A/C plug the main fan does indeed run. It looks as though this is not well known. I do not have an aux. fan as I removed mine since it didn't work. If I had an aux. fan I'd run out to the shop and try it. Sorry bud. 
Thread Starter
Pro
Joined: Nov 1999
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From: Woodland Ca
Originally Posted by coupeguy2001
if your fan is running all the time, check either the temp switch by pulling the wire off it,
1. if the fan keeps running, the relay is no good
2. if the fan stops, the temp switch is no good
1. if the fan keeps running, the relay is no good
2. if the fan stops, the temp switch is no good
Wouldn't this turn off the aux fan? Or is the only way to test it is to replace the relay?
Thanks
- 1986 Original Owner -
Joined: Apr 1999
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From: North Yorkshire, England
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Originally Posted by BIG K
So I disconnected the relay (next to the Master cylinder).
Wouldn't this turn off the aux fan? Or is the only way to test it is to replace the relay?
Thanks
Wouldn't this turn off the aux fan? Or is the only way to test it is to replace the relay?
Thanks
Thread Starter
Pro
Joined: Nov 1999
Posts: 659
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From: Woodland Ca
Originally Posted by Ray Quayle
Wrong relay for the Aux Fan. You really need a manual!
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Team Owner
Joined: Jan 2003
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From: Summerland B.C. Canada
Originally Posted by BIG K
OK, maybe I do. But the question is still valid...when I disconnect the relay, shouldn't the fan stop, or do I have to replace the relay to get it to stop?
There is NO WAY that fan can run if the right relay is removed, and the wiring is stock... 
Thread Starter
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Joined: Nov 1999
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From: Woodland Ca
Ok now, I replaced the relay and turned the key on. Even with out the engine running, the aux fan come on. On top of what I have done on this thread, I have also replaced the computerr.
Any more ideas?
Thanks!
Any more ideas?
Thanks!
- 1986 Original Owner -
Joined: Apr 1999
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From: North Yorkshire, England
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Originally Posted by BIG K
Ok now, I replaced the relay and turned the key on. Even with out the engine running, the aux fan come on. On top of what I have done on this thread, I have also replaced the computerr.
Any more ideas?
Thanks!
Any more ideas?
Thanks!
We need to all be playing from the same sheet of music.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
Originally Posted by BIG K
If I disconnected the air conditioner plug wire at the a/c, would this cause the aux fan to continually run? Even if the motors not running, just the key switch turned on?
Thanks!
Thanks!
Thread Starter
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From: Woodland Ca
Originally Posted by Ray Quayle
In the words of Dr. Lee "Something wrong here!". We are talking about the Aux Fan here, right? The one in front of the condenser? The one you can't see from the engine bay? The Temp Switch you pulled the wire on, was it the one in the driver side head between cylinders 1 & 3? Did a previous owner install a switch? Does it stop when you remove the relay on the shroud?
We need to all be playing from the same sheet of music.
We need to all be playing from the same sheet of music.
The temp switch I pulled was on the passenger's side...could this be where I am going wrong?
I installed all switches new less than 20k miles ago after sending the engine out for a long block rebuilt to Jasper's.
Yes it does stop when I remove the relay from the front of the shroud. I replaced it and I still have the same problem.
Last edited by BIG K; Oct 13, 2006 at 10:46 AM.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by BIG K
The temp switch I pulled was on the passenger's side...could this be where I am going wrong?
RACE ON!!!
Thread Starter
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Joined: Nov 1999
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From: Woodland Ca
Originally Posted by CFI-EFI
That SHOULD be the sending unit for your IP temp gauge. Turn the ignition to "On" and ground that wire. Does the aux fan run? Does the temp gauge go to 300°? That should tell you if it is the gauge sending unit or the fan switch. Now repeat the exercises with the wire from the device in the left head. The same results have the same indications. If all is right with the auxiliary fan wiring, the aux fan will run when the wire from the switch is grounded. That is how the fan switch activates the fan.
RACE ON!!!
RACE ON!!!
I just unhooked the switch on the driver's side. The connector on the switch is wide or bell shaped is this the one? Well anyway it did turn off the fan. I will replace it and see what happens.
Des this switch also effect that main fan also?