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Cooling fan problem-help?


Well-known member
Jul 18, 2001
Durham, NC
2002 Flat Black Z06
Hey folks,
I've run into a problem with the cooling fans. This is strange. After getting my rear gears swapped we used the original speed sensor which was a bad idea. So I get a SES light with code 24. That makes sense, Vehicle Speed Sensor. We're putting the right one in this week.
Now at the same time I got this error. The cooling fans have now decided that they want to go on a lot... Like now when I turn the ignition to on I get fans right away. If they don't come on then as soon as the car gets warmed up to say 180-197 water temp then fans come on and won't go off until I shut the car down.
Anyone have any ideas on this?

The 2 problems may not be related. This was the first time the Vette went for a 300mi (round trip) ride. So I may have had a part like a relay die on me or something.

Thanks, Graham
Hi there,
Your 2 cooling fan relays are located on the radiator shroud, on the drivers side, next to the hood prop rod.
If you want to do a quick test, just switch plugs, with the relays, as they are the same part numbers.
If it doesnt happen after that, you know that your relay was bad, and you should order another one.
The one to the front of the shroud is the primary, which I suspect to be bad.
Please keep us posted, c4c5:hb
thanks for responding. i was afraid it might be something worse. i'm going to swap them now and take it for a little spin and see what happens.
the one closest to the bumper is the primary?
does this mean the secondary will just run all the time instead of the primary if I swap the cables?
Ok I swapped the cables. Ran it. About 190deg fans come on. I checked it sitting in the garage and verified that both fans come on together and stay running.
What now?
Thanks, Graham
HI Graham,
You next move will be to use a scan tool, and see what the PCM is seeing for a temp, as you will also see a 'fan request ON or OFF'
This should be your next move. And when you swapped relay harnesses, you are simply changing the relay which is being used, so you automatically verified that your relays are good.
Besttoyou, and please keep us posted, c4c5:hb
Hi c4c5,
Thanks for the info. I'm going back to the shop Wednesday to get my speedo gears fixed. As soon as they are in we'll clear the computer and start again. If it acts up they will take a look at it while I'm in there.
It's rather odd that it happened as soon as the speedo gear kicked out and set the code 24. Now as soon as the SES light comes on the fans start...
I'll let you know what happens when I get back Thursday.
Im sorry, I must have misunderstood. I didnt think that the light was on all the time the fans were on.
This is a default, and it will happen until the code is cleared, and does not reset.
Besttoyou, c4c5:hb
no apology necessary. i appreciate any help i can get. and the people in the CACC are very good at that.
we got the right speed sensor in. the original was mangled. i'll post than in the gear thread i started.
as soon as we got the new sensor in the code 24 cleared out of the car and it now runs just fine.
what is bizzare to me is why the computer decided that it must turn both fans on when it gets that error. now i work on computers for a living. so i know they can do strange things...
but the computer sees the vehicle speed sensor is bad so there is no speedometer, so it decides, hey i should turn both the fans on and cool this thing down. huh? the coolant temp sensor was working just fine. the car wasn't hot. the AC wasn't on. interesting response by the computer...
i'd love to see the source code and flow charts for this operating system.
thanks, graham.

When in Doubt

Chill out

Yeah I suppose the default action on all these C4s is turn on the fans, it's probably hot anyway :)

Well I've heard a number of people say their Vettes are posessed. So I guess I got Hal... Maybe I should have kept the radio on and waited for that infamous message. "Sorry Graham, but I'm afraid I can't do that... :s

Thats a lot better that hearing your car tell you
"This car will self-destruct in 30 seconds." :L

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