Electric engine cooling fans--on/off????
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Electric engine cooling fans--on/off????
Lots of questions about when/what temps the electric engine cooling fan[s] runs at, assume some model years are different. Recently rebuilt the engine on my 87 convert. Didnt own car before rebuild so dont have a baseline for how the fan runs. Had to replace ECM and radiator as part of the rebuild process. Now fan runs whenever engine is running, even when engine is cool/first started. Assume fan may also be running at highway speeds too. Engine operating temps vary between 199 and 204, regardless of how warm/cold the day is. So is this right or wrong--most threads [perhaps newer c4s] talk about electric fan[s] operating between temp parameters?????
Burning Brakes
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Lots of questions about when/what temps the electric engine cooling fan[s] runs at, assume some model years are different. Recently rebuilt the engine on my 87 convert. Didnt own car before rebuild so dont have a baseline for how the fan runs. Had to replace ECM and radiator as part of the rebuild process. Now fan runs whenever engine is running, even when engine is cool/first started. Assume fan may also be running at highway speeds too. Engine operating temps vary between 199 and 204, regardless of how warm/cold the day is. So is this right or wrong--most threads [perhaps newer c4s] talk about electric fan[s] operating between temp parameters?????
Last edited by caddyboy84; Apr 8, 2012 at 02:05 PM.
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Nope--just the single primary "pull" fan in the cowling between the radiator and the engine. I replaced the thermostat with a 195 degree, the temp sensor is on the passenger side head, near the rear of the head. Also have the two sensors in the front of intake manifold--assume one in front feed the ECM and the sensor on pass-side back rear of head feeds the dash gauges. Anyway, believe the primary fan relay in on the fender next to the master brake cylinder????? Took the connector off that relay and it seemed to be oily--maybe the relay has failed or someone has by-passed temp controls. Still, its interesting that this/my 87 vette has one fan and according to the dash gauge, engine temp never gets above 205 degrees. Right now, A/C is disconnected so cant say how A/C would effect the fan's operations--probably not at all since the fan runs continuously.....with the engine.
Burning Brakes
Joined: Nov 2011
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Nope--just the single primary "pull" fan in the cowling between the radiator and the engine. I replaced the thermostat with a 195 degree, the temp sensor is on the passenger side head, near the rear of the head. Also have the two sensors in the front of intake manifold--assume one in front feed the ECM and the sensor on pass-side back rear of head feeds the dash gauges. Anyway, believe the primary fan relay in on the fender next to the master brake cylinder????? Took the connector off that relay and it seemed to be oily--maybe the relay has failed or someone has by-passed temp controls. Still, its interesting that this/my 87 vette has one fan and according to the dash gauge, engine temp never gets above 205 degrees. Right now, A/C is disconnected so cant say how A/C would effect the fan's operations--probably not at all since the fan runs continuously.....with the engine.
Last edited by caddyboy84; Apr 8, 2012 at 07:50 PM.
Team Owner
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From: Cincinnati, Oh USA
I own an 87.
The primary fan comes on at 228 F and the secondary fan comes on at 238 F. GM says to turn off the engine if the coolant temp reaches 260 F and let the engine cool down . They say this because 50% antifreeze at 15 psi boils at 265 F and the heads have the highest temp and boiling coolant cannot transfer much heat and the heads/valves could be harmed by excessive temp. If no boiling occurred, even 265 F will not harm an engine.
The primary fan on temp is controlled by software in the ECM from the temp sensor at the front of the engine under the MAF. The secondary fan on temp is controlled by a thermostatic switch in the block between cylinders #1 and 3.
When sitting in traffic that provides no air through the radiator, you should experience the main fan come on at 228 F and off at 211 F and then it will repeat. Underway, the coolant should settle at 195 F at the coolant temp sensor in the front of the engine with the factory thermostat which is 195 for an 87.
The primary fan comes on at 228 F and the secondary fan comes on at 238 F. GM says to turn off the engine if the coolant temp reaches 260 F and let the engine cool down . They say this because 50% antifreeze at 15 psi boils at 265 F and the heads have the highest temp and boiling coolant cannot transfer much heat and the heads/valves could be harmed by excessive temp. If no boiling occurred, even 265 F will not harm an engine.
The primary fan on temp is controlled by software in the ECM from the temp sensor at the front of the engine under the MAF. The secondary fan on temp is controlled by a thermostatic switch in the block between cylinders #1 and 3.
When sitting in traffic that provides no air through the radiator, you should experience the main fan come on at 228 F and off at 211 F and then it will repeat. Underway, the coolant should settle at 195 F at the coolant temp sensor in the front of the engine with the factory thermostat which is 195 for an 87.
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From: Anaheim CA
It depends...on what year you have.
The early cars had a main fan behind the radiator and an optional auxiliary fan in front of the radiator. The main fan is controlled by the ECM and the auxiliary fan is controlled by the temperature switch between spark plugs #1 and #3 in the driver's side head.
In later years (not sure when -- '90s or so) both fans are controlled by the ECM. The later cars have both fans behind the radiator.
If you have a stock temperature thermostat, it's 195 degrees (plus or minus some manufacturing tolerance). The temperature gauge on the dashboard usually reads about 10 degrees higher than the ECM temperature sender because the CTS (Coolant Temperature Sensor) for the ECM is located in the front of the intake manifold near the thermostat. The temperature gauge sender is between spark plugs #5 and #7 in the passenger side head. The water is a little warmer back there. The point is that the LOWEST temperature you're going to see on the gauge is going to be about 205 degrees in low speed driving. My car will run at about 230 degrees on a hot day with the A/C on.
The early cars had a main fan behind the radiator and an optional auxiliary fan in front of the radiator. The main fan is controlled by the ECM and the auxiliary fan is controlled by the temperature switch between spark plugs #1 and #3 in the driver's side head.
In later years (not sure when -- '90s or so) both fans are controlled by the ECM. The later cars have both fans behind the radiator.
If you have a stock temperature thermostat, it's 195 degrees (plus or minus some manufacturing tolerance). The temperature gauge on the dashboard usually reads about 10 degrees higher than the ECM temperature sender because the CTS (Coolant Temperature Sensor) for the ECM is located in the front of the intake manifold near the thermostat. The temperature gauge sender is between spark plugs #5 and #7 in the passenger side head. The water is a little warmer back there. The point is that the LOWEST temperature you're going to see on the gauge is going to be about 205 degrees in low speed driving. My car will run at about 230 degrees on a hot day with the A/C on.
Team Owner
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From: Summerland B.C. Canada
Fan operation form my 86 FSM
http://members.shaw.ca/corvette86/Co...%20Control.pdf
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Now this is getting interesting--this 87 only has the one main fan [directly behind radiator--no secondary]. A single green wire is connected to sensor on pass-side head, between 5 and 7. Replaced the temp sensor at front of intake manifold during rebuild. Am now curious about impact of A/C switch as compressor is disconnected and there is no freon in system. Drove home this AM [about 60 miles and 80 degrees ambient air temp.] Temp gauge on dash hovered between 199 and 206 all the way home????? Single fan seems to match fan cowling--suppose this could be an aftermarket fan????
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Le Mans Master
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From: Australia
Disconnect and jumper the pressure switch plug on the A/c line and see what happens
Last edited by rodj; Apr 9, 2012 at 10:26 PM.
