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Alt. locks under load

Old Apr 1, 2009 | 07:34 PM
  #1  
ATX-Iroc's Avatar
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From: Bastrop, Tx
Car: 87 Iroc-Z
Engine: 305 tpi
Transmission: 700-r4
Axle/Gears: 3.42
Alt. locks under load

My voltage drops to around 9v at idle ( checked with volt meter not guages) and comes back to 14v around 800 and above then drops off to around 10v at 2100 and higher. I just went out and cleaned all connections and tightened my belt. i noticed that when i spin the alt. pulley by hand there is a little squeak. I turn the car back on and notice that if i rev it with the lights and heater on the belt will squeal( yes its in great condition and has a good amount of tension) but if i turn the lights and heater off it doesnt squeal when reved. is my alternator bad
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Old Apr 1, 2009 | 09:42 PM
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ClickClickVroom's Avatar
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From: St. Aug
Car: 92 Z03 RS TBI
Engine: 5.0 L03
Transmission: T-5
Re: Alt. locks under load

it certainly sounds like an alt problem. I don't know if you've done it before, but alts come off with like 3 bolts. Pretty much any auto place (auto zone, advance auto, etc) will test it for you. Took 5 min when I brought mine in yesterday.
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Old Apr 2, 2009 | 12:46 AM
  #3  
sgt7n5's Avatar
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From: middleton, NH
Car: 83 z-28
Engine: 305 LG4
Transmission: T-5
Axle/Gears: 3.23
Re: Alt. locks under load

possibly the bearing is not doing its job so smoothly and under load it might be causing it to lock up
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Old Apr 2, 2009 | 09:39 PM
  #4  
8t2 z-chev's Avatar
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From: belle fourche,s.d.
Car: '82 z28
Engine: L83 5.7
Transmission: 700r4-1985
Axle/Gears: 3.42 posi
Re: Alt. locks under load

A worn pulley can cause the belt to slip under load
when the belt is good and has decent tension.
It is normal for alternator brushes to squeak a little
when turned by hand-14 v sounds good,but 9v at idle
10v above 2100 rpm sounds way low-batt volts should
be 12.5 or so without alternator working...
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