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Learned something about alternators today [message #221075]

Tue, 03 September 2013 19:10

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

Went by and picked up my alternator from Chap, the old guy who rebuilds them near me. Looked like new. While I was there, he showed me the original pulley and how it was worn from running a too small belt. While I watched, he pulled the old one off and installed a new one. As he was doing it, I noticed there was a small spacer behind the fan.

I asked him if it was possible to add spacers in order to get things in alignment. He said yes and gave me a handful of spacers of various thicknesses.

This photo shows the standard alignment:

http://www.gmcmhphotos.com/photos/data/6256/m_0052.jpg

http://www.gmcmhphotos.com/photos/data/6256/m_0052.jpg

And here are the spacers:

http://www.gmcmhphotos.com/photos/data/6256/m_0063.jpg

Because I had to remove the old alternator (purchased last week from Advance), I added spacers to both but installed the one that Chap rebuilt. I'll carry the other as a spare.

http://www.gmcmhphotos.com/photos/data/6256/m_007.jpg

http://www.gmcmhphotos.com/photos/data/6256/m_007.jpg

The belts are perfectly aligned now.

He also told me that if I laid a screwdriver on the back bearing cover while the motor was running, the magnetic field will grab it if the alternator is working and not if it isn't working. This is a neat little trick that I'd never heard before.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: Learned something about alternators today [message #221108 is a reply to message #221075]

Wed, 04 September 2013 07:34

Michael Leipold

Messages: 318
Registered: April 2011
Location: Greensboro NC

Karma: 2

Senior Member

Just a thought or a question...

But wouldn't putting the spacer behind the fan change the airflow going into the alternator?
Shouldn't the spacer go between the fan and the pulley?
I don't know if that is even possible, it is just a thought...

1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive Smile

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Re: Learned something about alternators today [message #221110 is a reply to message #221108]

Wed, 04 September 2013 07:53

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

Michael Leipold wrote on Wed, 04 September 2013 07:34

... wouldn't putting the spacer behind the fan change the airflow going into the alternator?
Shouldn't the spacer go between the fan and the pulley?
...

Yes, you can put spacers behind the fan or behind the pulley. I suspect that moving the fan 1/4" further from the front of the alternator would have some impact on how much air gets shoved into the alternator...not sure how much but obviously the further you are from an air source, the less it is felt.

I put the spacers in front of the fan and behind the pulley. I'm not sure why this was necessary. I'd have thought that the stock brackets would have positioned so a stock alternator is properly positioned but it was not. Not sure why.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: Learned something about alternators today [message #221112 is a reply to message #221110]

Wed, 04 September 2013 08:21

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Kerry Pinkerton wrote on Wed, 04 September 2013 08:53

<snip>
I put the spacers in front of the fan and behind the pulley. I'm not sure why this was necessary. I'd have thought that the stock brackets would have positioned so a stock alternator is properly positioned but it was not. Not sure why.

This is simple. If you had the alternator that came with THAT engine, the sheave would have the spacer as part of it (lower part count) and it would be at the correct offset for that FEAD (Front Engine Accessory Drive) on that engine. When they are being supplied to aftermarket, it needs to be able to fit as many as it can (again - to reduce inventory count). So, loose spacers.

I was once told that the old Sears Robuck design policy was,
"If you can't make it right, make it adjustable."

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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