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Its the electric radiator fan. It runs when the key is on.
On an 81, there is a thermal switch on the passenger side head. It operates the fan. I "assume" 79 is the same. It should only operate at 230* or so. Unplug it and see if it goes off.
79s still had clutch fans. Sounds like someone upgraded to electric and didn't wire it correctly. If so, I would get the wiring check asap. Might just need a fan control wiring kit.
79'L82./wAC Had an OEM aux. electric fan mounted in the shroud in front of the clutch fan. Should. Be a blue &black wire to a sensor in the passenger side cylinder head.
Last edited by speedreed8; May 1, 2017 at 10:41 PM.
79'L82./wAC Had an OEM aux. electric fan mounted in the shroud in front of the clutch fan. Should. Be a blue &black wire to a sensor in the passenger side cylinder head.
Yep- What he said. Both clutch fan and electric fan.
Mine runs from time to time, I thought it was purely temperature driven; I never checked to see if it turns on as soon as I turn the AC on or not. I can test later this week and repost back here. (If it does, I'd expect that it runs when defrost is selected too.)
Yep- What he said. Both clutch fan and electric fan.
Mine runs from time to time, I thought it was purely temperature driven; I never checked to see if it turns on as soon as I turn the AC on or not. I can test later this week and repost back here. (If it does, I'd expect that it runs when defrost is selected too.)
Adam
The auxiliary fan operates only on temperature--on at 238F and off at 201F--this operation is regardless of the HVAC mode setting. Also, A/C doesn't operate in the "DEFROST" position in warmer weather like in modern cars.\\
From what I've read here and elsewhere during normal operation the only time the electric fan should come on is with extended idling or low speed operation during hot weather with the A/C on. But again--it's not the HVAC mode selector that turn the fan on/of--only temperature. '79s (L82 in particular) are though hot running engines. If you notice top center of the temp gauge reads 220F instead of 200F as in other C3s and most other cars. Supposedly Chevrolet changed this after complains from '78 owners regarding the gauge being right of center during normal driving. I'm not sure what was done in '80 (perhaps the aluminum intake manifold?) but '80+ went back to 200F at top center of the temp gauge.
I know that the electric fan in my '79 L82 works but I've confirmed that it has never come on while driving. I have an Edelbrock aluminum intake manifold and true dual with no catalytic converter but otherwise it is stock with all original pollution controls functioning. Summer cruising around the point my Jimmy Carter speedo looses meaning is the only time I see temp above 220 but it seems to top out at about 230. During normal driving to include 55mph or so cruising it stays right around 200.
Last edited by SwampeastMike; May 2, 2017 at 04:44 PM.
Does anyone know if it's possible to replace the sender in the cylinder head with a different one and have the factory fan come on at a lower temp? Would love to have the fan on my 79 work at a lower temp.
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
When I was fighting overheat issues, I wired in a relay that powers the aux fan when the A/C is turned on. I think the original factory wiring was temp switch only.
Does anyone know if it's possible to replace the sender in the cylinder head with a different one and have the factory fan come on at a lower temp? Would love to have the fan on my 79 work at a lower temp.
Does anyone know if it's possible to replace the sender in the cylinder head with a different one and have the factory fan come on at a lower temp? Would love to have the fan on my 79 work at a lower temp.
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