sbm0301

I am having a problem tracking down the problem with my engine cooling fans. The fans work if the air is on but do not if off. I have replaced all three fan relays. The temp guage on the dash seems to be working correctly therefore I am assuming that the temp sensor located on the water pump is working correctly. My research so far is leading me to the PCM. Any ideas would be appreciated. Thanks

Sweet 90

The fans are programmed to start at certain temps. They will always come on when you turn the air on. You didn't say how hot you are getting but here is a guide line.
Temps for the fans would be about 205 degrees for the main fan and about 215 degrees for the aux fan. Both should be programmed to shut off approx 10 -15 degrees below the on temps.


Jim

Red Dwarf

Fan speeds for a 95 are "lo" at 227* "Hi" at 237* approx.

Sweet 90

Sorry guess i was off a bit

Jim

sbm0301

I have let the temp rise to about 235 before turning on the air. The fans didn't start. The fans do cycle when the car is started. I plan to replace the temp sensor. It's less than $20. Thanks

trulytex

You need to buy or borrow a handheld computer that plugs into the OBDII socket. You can go to a screen that tells you all of the data on your car in real time. You can see what the engine temp is, but you can also see if the ECM/PCM is "Requesting" each Fan. It will read "Requesting Fan 1" and "Requesting Fan 2" and will say either Yes or No. That is the best way to dignose this problem. If it is requesting the fan be turned on, then you either have a bad fan, bad relay, or bad connection.

trulytex

Did you ever find the problem????

sbm0301

I replaced the fan relays and the temp sensor. I then flushed the radiator. A mechanic shop down the street has offered to hook-up to the computer and check the PCM.

Thanks for all the help!

MK 82

Replacing the relays was a waste. If the fan run with the AC on, the relays are fine.

Your car uses three relays to allow the fans to run together with two speeds. They run in series for low and parallel for high.

sbm0301

I have had 3 vettes... But this one is it. It's a 95 Convertible - Red and Black. I originally wanted a Harley... but my Vette does it and more!

I'm learning and I want to thank all the "Senior Folks" for their input.

The car is working correctly but needs more TLC... a few more flushes or a radiator replacement but it's my Vette.

Your right about the money… but the experience was … “priceless”

Thanks,
Steve

Tmason

I have just the opposite problem, I replaced the temost sensor probe on the front of my 96 LT1 but my fans (both) run constantly. New relays as well and still the same. Suggestions