parafrog

paul just put my motor back together (brilliant). was doing function checks and figuring out which switch did what on the dash (i forgot about those stupid mid-80s 85 mph dashes), and since i don't have any tags yet, decided to test my fan on and off temps. nothing happened untill 235 (i kept an eye on the oil temp) when the secondary, front fan kicked--the primary fan did nothing, and i know it is controlled by the ecm. is there any reason why it shouldn't come on while parked, or do i have a problem. i definitely don't want to hit the road without a cooling fan. any suggestions?

also, there is a switch or sensor with an exposed single blade male connection on the inside passenger side, close to the top of the radiator without a wire or female connector in sight. the metal connector blade shows some corrosion, but the car has been sitting for three years so it is hard to tell if it has ever been used or not. any ideas on what this dohickey might be?

thanks, frog.

65Z01

You can test the main fan by jumpering the main fan relay Grn/Wht wire to ground with the ignition On. If the realy and fan are ok, the fan should then come on.

On an '85 Vette the main cooling fan relay is located on the firewall below the master cylinder.

If the main fan runs under the above test condition, open the AC pressure switch in the line near the blower motor and start the engine. The ECM should bring the main fan on, indicating it has fan control.

If that test works check the ECM coolant temp sensor, located in the front of the intake base under the TB. It is the sensor on the left, the one to the right is the Thermo Switch for the cold start injector.

parafrog

i just ordered a fan relay upgrade to 88 for $17 from ecklers. if it isn't the relay, then i'm out the money, but it probably needed replacing anyway. i don't think anything has been replaced on this engine. but i did just replace the coolant sensor.

speaking of ecklers, i found what looks like the single bladed radiator sensor--it looks like a low coolant sensor and it's in the right place for it. i don't know why there wouldn't be a wire to it.

thanks for the tip 65

frog

grapidssteve

I had a similar situation on my '85. Check the relay as stated above with the jumper wire, if the fan comes on then it is ok and likely the problem will be in the wiring. Remember, these cars are 20 years old and I know that I'm finding more and more issues with wiring and bad grounds.

Under the battery tray and master cylinder is an orange wire that comes off the positive battery terminal that can get corroded. This wire goes to the fan relay. Mine was shot, so no power was getting to the fan relay from there. When the jumper wire from the battery to the relay was in place, the fan kicked right on, thereby eliminating a bad fan motor or a bad relay as the problem. Swimming upstream was when we found the faulty wire right under the master cylinder. Spliced in a wire, correct color even, and I was back in business. Took 10 minutes, my beer had hardly broken a sweat.

I normally will have the a/c pressure switch removed on hot summer days or when autocrossing to have that cooling fan run to help keep the temps down. I noticed mine wasn't running at an autocross.

Hope this helps.