Electric fans run continuously

[mjlisz]

Hi Folks,

When I bought my 1990 corvette a few years back the electric fans behind the radiator ran continuously. This might have been a good thing since the car tended to run pretty warm, especially when going up a hill. Just last weekend I replaced the radiator and it now runs much cooler. In fact, it doesn't seem to quite get up to the operating temperature with the fans funning all the time. Does anyone know what might be causing the fans to run all the time? I would like to try operating the car with the fans running only when they need to.

Thanks,

Mike

 

[Vettefan87]

Do they run even with the car off? Do you have your AC on when the car is running? Or do the fans run nonstop as soon as you turn the key to the "on" position.
​

 

[mjlisz]

Hi Vettefan87,

The fans run nonstop as soon as I turn the key to the "on" position. It does not seem to matter if the A/C is on or not.

Thanks,

Mike

 

[gmjunkie]

Hi Vettefan87,

The fans run nonstop as soon as I turn the key to the "on" position. It does not seem to matter if the A/C is on or not.

Thanks,

Mike

My guess is that someone did a Bypass on the Fan wiring!!

 

[Fast Freddie]

gimme a fax number and i'll send you some mitchell-on-demand flow charts and wiring diagrams...

 

[Vettefan87]

Yeah somebody probably jumped the fans to start when the key turns on. Not really a bad thing since they are electronic.
​

 

[mjlisz]

Hey Folks,

Thanks for the help so far. I was able to determine that the ground wires going to the relays for both fans was tied to ground - obviously a previous owner modification. So I reattached the ground wires like there were supposed to be. Now the the left fan comes on when I turn the A/C on, or, when the temp gets about 3/4 up the temp gauge in the dash. But I have not been able to get the right fan to come on yet. Any ideas?

Thanks again.

Mike

 

[Vettefan87]

Probably has to get really hot, but I have heard others with the dual fan system saying that is how the fans are supposed to operate. I only have one fan and the stock temp to come on was around 230 I think. I had mine reprogramed to turn on at like 180ish.
​

 

[G Winter]

The right fan on my 90 seldom comes on. I hooked into the wires that were grounded on yours, use a DPST switch mounted in the dash ,hooked to ground. I can turn on both fans with the flip of one switch. The double pole switch keeps the grounds isolated when the switch is not turned on. In traffic on very hot days with air running it gives the cooling a head start.


Glenn

 

[Vettelt193]

did both fans used to work? I thought they are both supposed to run with the A/C on for some reason.

To test to see if the fans are wired up properly, you can get both fans to run by scanning the computer. If you don't have the little box that plugs in under the dash (or instructions on how to do this in general), then you can search for instructions on how to do it with a paper clip in this forum.

On my '93, I used to scan the computer while waiting my turn at the track, to get the fans to run with the car off without other wire hacking mods


If the fans run with while scanning, all should be ok. If they don't you have a bad relay, ground, or fan motor

 

[gmjunkie]

If the fans run with while scanning, all should be ok. If they don't you have a bad relay, ground, or fan motor

 

[mjlisz]

Folks,

Here is some moreinformation I was able to gather today. Mt service manual says that the secondary coolant fan (the right one) comes on when the colant fan switch (located on one of the A/C lines) is above 190 psi. So I removed the connector to the switch and the first thing I noticed is that the A/C did not come on at all with the switch disconnected. This may be normal. But when I shorted the terminals on the connector to simulate the switch being on, both the A/C and right fan came on. It does not make sense to me that the car is able to detect the switch to turn the A/C on but not the fan under these circumstances. What am I missing?

Regards,

Mike

 

[KOPBET]

I will say up front that I don't know if the 90 is the same as the 96.

However the 96 fans are designed to operate together either on low speed or high speed. If all is working correctly the fans must come on together at low speed when relay #1 (LtBlu, GRN, PNK wires) is energized because both fans are connected in series at that point. When all three relays are energized the fans are no longer in series and are grounded separately and run at high speed. If only the left fan comes on I would suspect relay #3 (DkBlu, PNK, WHT wires) is stuck in the energized position (either mechanically or electrically independantly of #2). If stuck mechanically, then switching the two relays would cause the both fans to run continuously at slow speed.

 

[Fast Freddie]

i hope the files i tried to attach show up.

 

[topless82vette]

My friend has this problem with his 1990. Both fans run all the time from the time you turn on the key. I know no wiring mods have been done to the car, the a/c compressor is not running when it does this either. So what can cause this is the ecm causing the fans to do this?