Fan Noise

[Bob703]

My 37 Ford came with a 12-volt conversion along with a GM alternator. The alternator has the pulley fan mount on which is mounted the original 4 blade fan. I've always heard a whining noise that changes with engine speed. Sounds like the car has a blower. I've been told that 4 blade fans are noisy, so I removed it to see if the sound went away. Well, it did, almost entirely but I still hear a little.

The prior owner didn't have the car very long and either have I. So, I would be surprised if the alternator bearing went bad so fast. But maybe. Before a buy another alternator I was wondering if changing the fan would improve things.

I have also read that 2 bladed, aluminum fans moved more air. any suggestion? Thanks

[flatford8]

If the bearings in the alternator weren’t up to the task of supporting the fan, it would take the bearing out sooner. If you’ve removed the fan, and still hear a whine that’s what I would suspect has happened……..Mark

[Kube]

Originally Posted by flatford8

If the bearings in the alternator weren’t up to the task of supporting the fan, it would take the bearing out sooner. If you’ve removed the fan, and still hear a whine that’s what I would suspect has happened……..Mark

Yes sir... I'm with you 100%.

[flatford8]

If you’re committed to using an alternator, an electric fan in front of the radiator as a pusher or behind the radiator as a puller, maybe your best option…….Mark

[40cpe]

Take a look at replacing the front bearing in the alternator. The ones I've changed are simple to do.

[Drbrown]

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Find a local electric shop. Mine can test alternators and replace bushings/bearings/diodes as needed. Re fan noise, my engine has an after-market six-blade fan - also noisey when shifting thru the gears. On the highway far less noticable. I tried an electric fan but had to put a larger alternator and it was insuficient in city traffic. So went back to the engine fan. I hear a few people have adapted a modern temperature-sensitive fan clutch.

[DaleandNatalie]

There are a lot of inferior parts out there so I wouldn’t be surprised at all with a fairly new alternator making noises, have seen it many times.

[Drbrown]

I went thru a time when the (off-shore) Alternator I bought burned-out the Pentrox ignition that came in my car ... they would spike higher than 14.5 volts. So after discovering this I took the brand new alternator to my local elec shop and had them test it befor einstallation. I aslo installed a volt meter in the system. An aside ..... the Pentronix was so troublesome and expense I changed back to a stock points distributor.

[rotorwrench]

The alternators can start whining if the diode bridge gets compromised but that noise is pretty distinct for those that have experienced it. Ford set their generators up with some pretty heavy duty bearings for those mounting a fan. Alternator bearings are reliable until this type of mod is added. Some folks go with an offset mounting for the alternator and use a modified generator front support to locate the old type fan.

[KiWinUS]

That alternator is probably not designed to work with the loads that fan puts on it.

[tubman]

Originally Posted by Drbrown

I went thru a time when the (off-shore) Alternator I bought burned-out the Pentrox ignition that came in my car ... they would spike higher than 14.5 volts. So after discovering this I took the brand new alternator to my local elec shop and had them test it befor einstallation. I aslo installed a volt meter in the system. An aside ..... the Pentronix was so troublesome and expense I changed back to a stock points distributor.

A not uncommon occurrence.