cooling fan problems
Thread Starter
2nd Gear
Joined: Mar 2008
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cooling fan problems
Hi i have a 87 corvette, in which the cooling fan will not turn, i have replaced the ECM, cooling fan relay, and temp switch in the block but it still will not come on when it get hot, is there anything else i can check or replace, when i short out the relay connector the fan will come on, so i am at a lost here, can anyone help!!
derek
derek
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Joined: Dec 2000
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From: SE NY
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The coolant temp sensor is located below the TB in the intake base. This is the sensor that the ECM uses to determine when to turn on the main fan.
To test this sensor measure the resistance cold and hot; the resistance value should drop greatly when hot.
To test that the ECM can bring on the main fan, open the small connector in the A/C coolant line (near the dip stick tube) and the fan should run.
To test this sensor measure the resistance cold and hot; the resistance value should drop greatly when hot.
To test that the ECM can bring on the main fan, open the small connector in the A/C coolant line (near the dip stick tube) and the fan should run.
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Joined: Sep 2000
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From: The Top of Utah
The only temp sensor in the block is just above the oil filter at the left rear of the block. It is for the oil temperature. The main fan is controlled by the ECM. It uses the same sensor 65Z01 pointed out for all it's functions, including cold start mixture and cold idle speed. Are you getting the engine warm enough for the ECM to switch the fan on?
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Team Owner
Joined: Mar 2001
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From: Cincinnati, Oh USA
The main fan comes on at 228F and the aux fan at 238F. The temperature switch between cylinders 2 and 4 only turns on the auxilliary fan. Ignition in run, if you ground the green/wh wire on the fan relay, the main fan should run. Check the 3 amp c. fan fuse with an ohmeter.
- 1986 Original Owner -
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From: North Yorkshire, England
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Race Director
Joined: Sep 2000
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From: The Top of Utah
He must. The heads aren't drilled and tapped, there. The aux fan switch, if the car has RPO# B4P, is in the left head between the front two (#1 & #3) spark plugs. No B4P? The hole has a plug in it. Either way, that has no bearing on the main fan operation.
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Thread Starter
2nd Gear
Joined: Mar 2008
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thank you for all your help i will try the coolant temp sensor under the TB. That is the only sensor that i have not replaced, the air conditoniar compressor doesn't work, does that have anything to do with the main fan not coming also?
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Joined: Sep 2000
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From: The Top of Utah
Quit throwing parts at it. I don't know what "temp switch in the block" you replaced, but that and changing the "ECM, cooling fan relay" all haven't helped. Does the engine have a fast, cold idle? If it does, that is a sign that the ECT sensor under the TB is working. If in doubt, it can be tested. As jfb posted, the ECM doesn't start the fan until the coolant reaches 228°. Are you getting it warm enough to call for the fan?
The fan should also come on when the ECM receives a signal from the A/C pressure switch, but with the air, off, or with a bad compressor there is no interference with the thermal operation of the fan.
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The fan should also come on when the ECM receives a signal from the A/C pressure switch, but with the air, off, or with a bad compressor there is no interference with the thermal operation of the fan.
RACE ON!!!
