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Author Topic: Alternator "drag" increases with RPM's?  (Read 5598 times)

Jbray

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Alternator "drag" increases with RPM's?
« on: August 26, 2010, 10:18:22 AM »
1984 class a motorhome on chevy P-30 series with 454. This MH sat unused for a couple of years. When purchased I was aware that alt. was not charging. Inspection determined there was no alt. belt. I have installed 2 belts with the same result. At low rpm everything is fine. As RPM's increase, so does belt squeal, until it jumps or breaks. The belt turns the Alt and AIR pump. Nothing else. pulleys appear to be aligned properly. Alt and AP turn freely w/o belts. Can the Alt rotational resistance increase with RPM? (more than just charging resistance?)

Thanks.
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Alternator "drag" increases with RPM's?
« on: August 26, 2010, 10:18:22 AM »

drew

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Re: Alternator "drag" increases with RPM's?
« Reply #1 on: September 10, 2010, 02:17:56 PM »
I'm not sure why this would be happening. My first thought is that the voltage regulator might be bad. Resulting in a current directly proportional to the battery being leaked into the rotor. At low speeds this would be okay, but as the rotation speeds up, the current would increase. A cascade effect would happen and the charging resistance would be very high. Another possibility could be a physical blockage or bearings failing only at high speed. I will study this problem more and get back to you.

Jbray

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Re: Alternator "drag" increases with RPM's?
« Reply #2 on: September 17, 2010, 08:15:22 AM »
Thanks for the reply Drew. However, the drag was increasing because the bearings were siezing. (I thought it was AIR pump, which was also getting stiff.) I am doing the headers, x-pipe and cold air intake now. When I get to the alternator I will have to ask you how to test if alternator just needs bearings, or just exactly how to fix it. Maybe not worth it. Thanks again!

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drew

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Re: Alternator "drag" increases with RPM's?
« Reply #3 on: September 17, 2010, 02:23:19 PM »
Testing bearings is usually really easy. Bad bearings will usually spin unusually freely. A good bearing will feel very smooth, but with a small resistance from the lubricant. There's a really good bearing kit at store.alternatorparts.com. Part #522. Here's a link http://store.alternatorparts.com/522-alternator-bearing-kit-6302-needle-bearing.aspx That should work, I looked up the 1984 P30 with the 454 and you should have either the CS144, 10Si, or 12Si series alternator and this kit fits all three.