Is fan clutch working properly?

[Gary N.]

How do I know or test the fan clutch on my 66' air coupe. It seems to heat up very fast when I have to stop at a red light with the A/C on? It has a five blade fan. I spun the fan when the engine was cold and then again after the engine had been running hot and it seemed that the resistance of the fan clutch was about the same for each. I noticed that when I do this with my chevy surburan the blades seem to make a much louder sound and moves much more air when I start out from a stop. Just wondering if the fan clutch on the vette is working correctly. Shouldn't the fan clutch offer more resistance when hot to move the fan more?

[Rich G.]

Re: Is fan clutch working properly?

You should feel a difference hot and cold. Also, if you start the car cold and stand by with the hood open you should hear the clutch engage when it gets hot enough and feel the warm air coming back from the fan once the fan clutch engages. I replaced the fan clutch on my 66 327/350 a couple of years ago and noticed these differences after I changed it.

Another cause of heating at idle has to do with having the correct vacuum can and proper timing. There have been many threads on that topic and Duke Williams has written on the subject a number of times.

If you suspect the fan clutch, I would change it. They are not expensive and you don't need an exact replica or original just to prove that your current one is defective.

Good luck.

Rich

[Gene M.]

Re: Is fan clutch working properly?

The Corvette fan has an offset blade spacing to keep them quiet. Also notice the pitch of the newer stuff moves more air thus the windage noise. More often the newer blades are bigger so that makes more audible too.

For driving I have a Pontiac 7 blade fan and clutch from an older vintage. Not sure which. Mounting, diameter and length are identical to original. But noise is no different than the 5 blade original but it does seem to cool better. More noticeable while idle and slow speeds. I do have Vintage air on my 65.