C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

The story of the 2 Fans

Old 03-14-2019, 12:23 AM
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Default The story of the 2 Fans

On my 89 I have a fan in front of the radiator (opposite side of engine) and one behind the radiator (same side as the engine). The one in front of the radiator comes on immediately and I believe never stops; the one behind the radiator never seems to come on, even at 200+ degrees....what should be happening? How to repair? I just completed a head gasket and want to take all of the preventative measures I ran across a fan conversion kit, the fan comes on at 200 and cools down to this my solution? Thanks.

Last edited by woodcrest; 03-14-2019 at 12:28 AM. Reason: new info
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Old 03-14-2019, 08:33 AM
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From factory, the Main fan behind the radiator should come on at about 228F coolant temp. The aux fan at about 235-238F, it did vary a couple degrees through the years. The thermostat doesn't open until 195F.

The main fan should be controlled by the ECM, if its coming on sooner then someone has either put a switch in place, or the chip has been changed to do that. Preferably you leave it in ECM control, because the ECM will kill it once you get over ~35mph (forget the exact value) because its detrimental to cooling once youre at speed.

The aux fan on-temp can be controlled by changing a switch in the drivers side head between 1 & 3. There are aftermarket switches you can put in place from Ecklers/Midamerica/etc.

So theres a lot you can do, you can swap to a 180F stat and prolong the amount of time it would take to get hot, you can change the fan on-temp to say 210-215F and off at 195F, the aftermarket aux fan switches come on at 195F I think. The best thing is to add a DeWitts radiator, it'll take a very hot day in traffic to make a car overheat once you've upgraded the radiator to one twice the size of stock.
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Old 03-14-2019, 10:18 AM
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I had a similar, but not exactly the same, [email protected] 232 the aux (front) fan would cycle, but the main wouldn't run at all....turns out my coolant temp sensor in the front of the engine must've gone lazy, not telling the ECM the correct temp. One new CTS later & the main works as designed...
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