Cooling Fans
Thread Starter
Instructor
Joined: Aug 2005
Posts: 112
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From: Lone Tree CO
Cooling Fans
I just got my 93 vette 6 weeks ago. I had no idea this was such an involved process of keeping LT1's cool.
This last week I was driving with the AC off and noticed the temps @ 220 with the fan not kicking on, it has a manual switch so every time it got to 200 I would turn the fans on and when it got to 175 I would turn them off which was a PITA. Previous to this it nomally ran between 185 and 195 with the AC on. So I thought the relay might be bad, so tonight when I went to change the relay I happened to have the AC on and noticed the fan was working and the temp held steady @ 185. Soon as I turn the AC off the fan quit and the temp was over 200 in minutes and the fan did not kick on, do I have to wait till 230 to see if it will kick on? It sound like this is normal from other threads I have read. Isn't it strange that the car will run cooler with the AC on than off, or am I not getting something here?
Ken
This last week I was driving with the AC off and noticed the temps @ 220 with the fan not kicking on, it has a manual switch so every time it got to 200 I would turn the fans on and when it got to 175 I would turn them off which was a PITA. Previous to this it nomally ran between 185 and 195 with the AC on. So I thought the relay might be bad, so tonight when I went to change the relay I happened to have the AC on and noticed the fan was working and the temp held steady @ 185. Soon as I turn the AC off the fan quit and the temp was over 200 in minutes and the fan did not kick on, do I have to wait till 230 to see if it will kick on? It sound like this is normal from other threads I have read. Isn't it strange that the car will run cooler with the AC on than off, or am I not getting something here?
Ken
Team Owner
Joined: Oct 2000
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From: 63.8% of all statistics are made up on the spot.
St. Jude Donor '08-'10
I have an L98 so this could be wrong but I believe that the ECM turns the fan on at 238. The fan is supposed to come on anytime that the a/c is turned on to help with the extra cooling needs.
Race Director
Joined: Feb 2003
Posts: 11,672
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From: Lake Wylie SC
One more thing to remember is that your fans don't need to be on above 35 mph. That's why GM has a VSS that tells the ECM to turn off the fans above 35mph. So, if you have your fans on manually above 35 mph, you are running them too much and it may shorten the life of your fans. The 228 and 238 temps given above are close and are there for a reason; emissions. The fans always come on if the A/C is on, again up to 35 mph. Just make sure your radiator and condensor are free of debris.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
Both fans should be on whenever a/c is requested and speed is less than 35 - 40 mph. PCM signal is from the a/c pressure switch. Otherwise, PCM will ground the main fan relay at 219 and turn it off at 208; secondary at 228 and off at 217 - speed less than 35 - 40 mph. Signal is from the Engine Coolant Temp Sensor. Use a scanner to verify Engine Coolant Temp Sensor reading and that the PCM is commanding the fans to come on within specs. If the fans are coming on when they should (non a/c), but no appreciable temperature drop occurs until the secondary fan kicks in, suspect restricted air flow or a plugged up cooling system. If both fans aren't coming on until the secondary fan temp, whomever wired up the manual fan switch may have knocked out PCM control of the main fan. I'd get rid of it and make it work as designed.
Drifting
Joined: May 1999
Posts: 1,478
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From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
Originally Posted by joecaver
I have an L98 so this could be wrong but I believe that the ECM turns the fan on at 238.
Originally Posted by Wayne88
The main fan comes on at about 228, and the aux fan at 238.
According to the GM Factory Shop Manual the 1988 L98 main fan comes on at temps above 108*C or 226*F. (See page 6E-C12-4) The aux fan is activated at 109*C or 228*F. (See page 8A-31-1) The 93 LT1 probably differs from the L98 by the amount that SunCr states.
The dash coolant readout value you see in L98s (and maybe LT1s?) comes from a different sensor than the ones used to activate the main or the aux fan. Your dash readout may not match the value used by the ECM for the main fan or by the Coolant Fan Temp Switch, which controls the Aux. fan. It should be close though. If not, then I'd have the sensors accuracy checked.
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Thread Starter
Instructor
Joined: Aug 2005
Posts: 112
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From: Lone Tree CO
Thanks for all the input. I actually tested the fans tonight. Without AC the fan came on at exactly 228 and shut off at 217. When I turned the climate control on it ran at a steady 190.
Melting Slicks
Joined: Jun 2000
Posts: 2,965
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From: North side of Houston Texas
I had the same exact problem in my '92, only my primary fan wasn't kicking on at all. I put in a Hypertech chip and not only did it fix that problem, but I got a few extra ponies out of it to boot.
