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My 79 camaro has a 65amp alternator that will not start charging, unless I rev the engine once passed 1700 RPM. At night, with the lights on and 16" electric fan running, I've got to hold the idle speed at 1000 RPM to keep the alternator charging above 13.5 volts. Otherwise my lights go dim, and volt meter drops below 12 volts. All my accessory pulleys are factory; No Under Drive Stuff here. Please advise

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Loose or barely slipping belt come to mind.

Barely slipping? Belt slipping but you don't hear the squeal, it's so high pitched.

Time for a new alt?

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Everett 68/350/PG/11.90/115mph
 

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I am not sure on your year of car how hard it is to remove the alternator, but almost every parts store from Napa to Pep Boys will test it for you for free. My '67 was doing the same thing and the alternator was bad. And it was brand new! I would check belt, alternator and voltage regulator. The problem should be found in one of these three areas.
 

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he says the pulleys are factory, but maybe he stumbled across a smaller crank pulley or something funky like that? add in a slipping belt with a low idle speed, and you might have problems. or maybe the alt is just flat out too small for the application. headlights and a big electric fan put a lot of strain on the charging system.

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1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
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For some reason, that always happens to me. I think the wiring harness might be the culprit in mine, cause the accessories can't draw enough current through the old wiring.

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1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my NEW webpage at: http://www.geocities.com/compuboy007/
 

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It's your electric fan. These things draw insane amounts of current. A black magic fan will draw 35 amps, no alternator will put out that kind of current at idle. Combine that with another 10 amps to light your low beams your at 2/3 the rating of your alternator. probaly 3/4 if your running high beams.

Alternators are not rated to produce max current at idle, and most will only produce 1/4 or less at idle. You need to either increase the speed of the alternator (undersize the altermnator pulley) or decrease your electic load.

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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine
 

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Discussion Starter #9
Thanks for all of the replys and ideas.

The alternator checks out perfect at Auto Zone, as well as NAPA.

The pulleys are as I said before; OEM Factory items - no question about it.

All of my chassis and instrument panel grounds are clean.

Do I need to update the main engine compartment wire harness 12 volt supply wiring, to support an 11 amp electric fan? I've caught 3 places on the web discussing this matter, and that pre electric fan vehicles lacked the required gauge of wiring. I'm a little confused, on account the electric fan is directly wired to the battery (using the supplied harness) and activated VIA the supplied harness relay. It just doesn't add up. Does anyone make an "OVERDRIVE" pulley for a GM 65amp alternator, or know where I can salvage yard an OEM one from another GM vehicle?
Thanks.
 

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It may be more than you want to spend, but there are alternators that produce much more than stock ones at idle. Powermaster makes them that put out 70 and 80 amps at idle with 140 amps total. I'm currently using the 80 amp CS style on my 69. Since I have an aftermarket ignition, EFI, electric fuel pump, dual electric fans, electric vacuum pump, A/C, etc. I needed a solution. This was what worked for me. I can have everything going including lights and have no problems at idle.

Jody
 
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