C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

How does aux fan activate?

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Old Aug 16, 2009 | 05:18 AM
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Default How does aux fan activate?

Can't seem to get the front aux fan to operate. How is it activated?
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Old Aug 16, 2009 | 05:29 AM
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Either by letting the temp get up to 230, or, if I´m not mistaking by grounding A and B on the ALDL.

Check the aux-fan relay (should be under the hood somewhere), someone with a 88-89 will chime in I guess to tell you where to find it or it´s in the FSM if you have it...
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Old Aug 16, 2009 | 07:21 AM
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Originally Posted by vette079
Either by letting the temp get up to 230, or, if I´m not mistaking by grounding A and B on the ALDL.
Grounding ALDL only makes main fan run , no ECM control of aux fan
'89 aux fan is by mech switch only.Pull the wire off the switch (drv side head between #1 & 3 ) and ground it.Fan should run. Lower temp switches are available; stock is 235+

Last edited by rodj; Aug 16, 2009 at 08:59 AM. Reason: screwed up
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Old Aug 16, 2009 | 07:38 AM
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Originally Posted by rodj
Grounding ALDL only makes main fan run , no ECM control of aux fan
'89 aux fan is by mech switch only.Pull the wire off the switch (drv side head between #1 & 2 ) and ground it.Fan should run.Lower temp switches are available; stock is 235+
Maybe it´s the same on my 91 then, been awhile...
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Old Aug 16, 2009 | 08:34 AM
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On a 1989 the aux fan switch/sensor is in the head on the drivers side between plugs 1 and 3. The main fan is ECM controlled.
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Old Aug 16, 2009 | 08:58 AM
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Originally Posted by vette079
Maybe it´s the same on my 91 then, been awhile...
No both your fans are controlled by the ECM
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Old Aug 17, 2009 | 06:33 AM
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Originally Posted by rodj
No both your fans are controlled by the ECM
The pusher in front of radiator is controlled by a thermal switch between 1 & 3 cylinder.
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Old Aug 17, 2009 | 07:27 AM
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Originally Posted by kenmohr
The pusher in front of radiator is controlled by a thermal switch between 1 & 3 cylinder.
Correct
as I previously stated above but only pre '90 cars which have the aux fan in front of radiator.

90+ cars have both fans on engine side of radiator and both are controlled by ECM.There is NO switch in the drv side head
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Old Aug 17, 2009 | 11:12 AM
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Originally Posted by kenmohr
The pusher in front of radiator is controlled by a thermal switch between 1 & 3 cylinder.
Thanks guys. What is the best way to test it?
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Old Aug 17, 2009 | 03:59 PM
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Originally Posted by jerkyboy
Thanks guys. What is the best way to test it?
Take the wire off the thermal switch and ground it with the key on.
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Old Aug 17, 2009 | 06:57 PM
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...and from now on include the year vette you are asking questions about so you can get better advice.
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Old Aug 17, 2009 | 07:25 PM
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Even if it works, take it out and sell it, it's extra weight! Mine ran a little cooler at cruise without it. I think it may be a benefit to have if you have A/C.
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Old Aug 17, 2009 | 08:39 PM
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Not all Vette's have this option and they cool fine - in fact if it's coming on at all, that usually means something else is wrong and it has nothing to do with a/c - it isn't even linked to it (and if a plugged up a/c system gets the coolant hot enough that it needs to come on it's probably going to blow a hole in the hood before you get a chance to see if it's running). Keep the a/c off and block airflow - I stick mine up against the garage wall when it's 90 or better. That will usually get it to the threshold to come on and while looking at a scanner you'll see what the Coolant Temp Signal is when it starts cranking.
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Old Aug 18, 2009 | 08:34 AM
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Originally Posted by jfb
...and from now on include the year vette you are asking questions about so you can get better advice.
It's not in my sig?
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Old Aug 18, 2009 | 08:38 AM
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Thanks SunCr!


Originally Posted by SunCr
Not all Vette's have this option and they cool fine - in fact if it's coming on at all, that usually means something else is wrong and it has nothing to do with a/c - it isn't even linked to it (and if a plugged up a/c system gets the coolant hot enough that it needs to come on it's probably going to blow a hole in the hood before you get a chance to see if it's running). Keep the a/c off and block airflow - I stick mine up against the garage wall when it's 90 or better. That will usually get it to the threshold to come on and while looking at a scanner you'll see what the Coolant Temp Signal is when it starts cranking.
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Old Aug 18, 2009 | 09:11 AM
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Here is the way I see it. If the person requesting help can't put the model year in his request, why should I bother to look it up.

Especially when he has a bugle in his butt.

Originally Posted by jerkyboy
It's not in my sig?
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Old Aug 18, 2009 | 01:47 PM
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Incredible.
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Old Aug 18, 2009 | 01:57 PM
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I think some people have sigs disabled.
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Old Aug 18, 2009 | 02:06 PM
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Originally Posted by Aardwolf
I think some people have sigs disabled.
Exactly!
Because some users chose to have huge pictures as part of their signature.
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