Hi Aldo!

Good news! I have figured out what is wrong with your temperature gauge and fan control switch.

Here is a temperature sending unit for a 1979 Corvette....
http://www.autozone.com/R,APP263592/...ductDetail.htm
Here is a cooling fan switch for a 1981 Corvette, does this look like the one you have?
http://www.autozone.com/R,APP228084/...ductDetail.htm
It seems to me that someone added the electric cooling fan to your car and changed the temperature sending unit for the temperature gauge to a cooling fan switch instead. This would explain why your temperature gauge does not work. To the best of my knowledge the 1979 Corvette did not come with an electric cooling fan.
Here is what I would do.
1. Get a temperature sending unit for your temperature gauge and install it, either on the head where the double prong fan switch is (remove the old fan switch and throw it away), or on the intake manifold at the upper radiator hose connection (thermostat housing). Connect your temperature gauge wire to it - I'll betthe gaugeworks now.
2. Get a new fan control switch and install it in the other location from the temperature sending unit, then connect your fan to itOR - Remove the electric fan and fan switch as they were not original to your car anyway.



[sm=icon_cheers.gif]

 

Good idea DV8, aren't both heads the same, can he put the temp guage sending unit on the left head between cly #1&3 and put the fan switch sending uniton the right head between cly # 6&8? PG.

 

Hi DV8,

thanks for the sending units links...

I think anyway that my auxiliary fan is original...
on the fuse panel there's a fuse " auxiliary fan"

and look at these pages on the 79 assembly manual. my auxiliary fan and sending unit are exhactly as in the drawings. the only difference is that the wires from the fan are arranged differently.

Anyway i was thinking to do a different thing : instead than connecting the fan to the switch,I'll place a manual switch aside to the auxiliary fan fuse and so manually control the fan from the inside of car when I see the temp going too high on the temp gauge ( that is now working but it measure something less - about 20°F less)

[IMG]local://upfiles/6949/BA126A56ADBA42A594E2DB1AC4C46FA7.jpg[/IMG]

[IMG]local://upfiles/6949/D641B89B4BC74474898E868FC0CF9185.jpg[/IMG]

[IMG]local://upfiles/6949/439F7473249044848B22994B2B1BACE6.jpg[/IMG]

 

Aldo, How ya' doin' ?
The manual switch is fine. The only thing is that it's just not as convenient. It's much nicer and safer to have the fan come on so as to keep the engine running at a constant friendly temperature instead of waiting for the temp to go up prior to flipping the switch. I would probably get talking and forget about watching the temp gauge.
I say get the fan working w/ an automatic switch that comes on at the proper temp.
By the way, "hats-off" to you for the constant work you do on that 'Vette of your's.

 

Since the eletric fan is referred to as an auxiliary fan, is there still an engine mounted fan also?

 

Yes

 

Wow, I learn something here every nite. I must have slept thru that change. Any idea what year they started that?

 

yesterday I received the shop manual (great!!!) and I checked something about the Corvette "fans"...

-Auxiliary fan.the oem switch for the auxiliary fan goes ON at 238°F and then OFF at 201°F. In my opinion this auxiliary fan starts when it's too late! I think I should go for a lower temp switch or manual switch ( the problem is that the adjustable switches from summitracing are quite expensive...)

-engine fan. I still don't understand how the fan clutch works.
I read in the shop manual that the fan clutch is temperature controlled ( mechanically I suppose, because there's no electrical device). the manual says that the clutch engages when the air coming from the radiator surface is at 180-190°F. But I have read somewhere else ( not in the manual) that the clutch engages at low engine rpm and disingages at hi-rpm because it's supposed that being the car at high speed, the air from the chin spoiler is enough to cool the engine.

where's the truth?

I like very much the way in which the shop manual explains the things. Not only how to repair but first how things works. For a motors newcomer like me , it's really a great reading, even if I have nothing to repair ( my brakes doesn't leak oil, for example, that seems quite a miracle for a Corvette)

 

I put in black magic dual electric fans (PN 279) in november of last year. There is a big difference in how my car performs because of them.

They wire directly to the alternator and have a very nice fan control system.

You put a therm in between the radiator, It has a dial on the front of the control box ,you turn it either left or right. Left is cool and right is hot.

It allows you to set what temp you want your fans to come on. The other amazing feature about these fans is that when you turn your car off the fans keep going until your engine has been brought back down to a safe temp which can really prolong your engine life.

The only downside to them is that You need to upgrade your alternator to use them. I had to go from a stock 63 amp one to a 140 amp one from ecklers to keep my battery from dying.

 

I can't see where I would have room for the engine fan, unless I used pusher elec. fans in front of the rad. I've been goin' by the idea that the elec. puller fansystems replace the original engine fan.

BTW, the fans staying on after the engine is turned off, only cools the water in the rad, since water is no longer being circulated through the engine.