Electrical/Alternator question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

miket · 01-16-2003, 10:44 PM

Hoping someone can give me a clue here...

My 71 had the original voltage regulator setup. I had a spare 10 SI internally regulated alternator (63 amp) that had gone bad. I picked up a rebuild/upgrade kit from here (http://www.alternatorparts.com/alternators_gm.htm) as well as a conversion harness from here (http://www.wiringharness.com/custommods.htm). In two hours I rebuilt my alternator and installed it along with my conversion harness.

Unfortunately, it did not get rid of my lights dimming at idle in gear and flaring on acceleration. I checked voltage at the alternator and at idle and it was putting out roughly 13 volts...if I revved the engine slightly it jumped to 13.65-14.20. I checked it at the battery and had roughly the same readings....

Any ideas?

O'l Buck · 01-17-2003, 02:40 AM

You might check your grounds, the battery cable ground, the engine to cab ground, and the cab to frame ground. Bad grounds will do some crazy stuff, mine used to flicker the lights and shut the radio off everytime I hit a bump.

JimKshortstep4x4 · 01-17-2003, 09:50 AM

Based on your description, I believe that the regulator in the alternator is defective.

Jim

Longhorn Man · 01-17-2003, 10:44 AM

Even though the alt is 10 times better than a generator, it is hard to build one that can operate in the whole RMPM range that they are needed to work in (aka...650 RPM to 5500 RPM) So they designed it to not work too well at idle.
At least, this is what my alt rebuilders told me. I find it to be normal with older vehicles. You can speed up the alt by installing a smaller pully on it, or a larger one on the crankshaft...the oposite of an underdrive set up.

01-16-2003, 10:44 PM	#1
miket Registered User Join Date: Jan 2003 Location: Seattle WA Posts: 1,466	Electrical/Alternator question Hoping someone can give me a clue here... My 71 had the original voltage regulator setup. I had a spare 10 SI internally regulated alternator (63 amp) that had gone bad. I picked up a rebuild/upgrade kit from here (http://www.alternatorparts.com/alternators_gm.htm) as well as a conversion harness from here (http://www.wiringharness.com/custommods.htm). In two hours I rebuilt my alternator and installed it along with my conversion harness. Unfortunately, it did not get rid of my lights dimming at idle in gear and flaring on acceleration. I checked voltage at the alternator and at idle and it was putting out roughly 13 volts...if I revved the engine slightly it jumped to 13.65-14.20. I checked it at the battery and had roughly the same readings.... Any ideas?

01-17-2003, 02:40 AM	#2
O'l Buck Recovering Truck Driver Join Date: Mar 2002 Location: Orleans, NE USA Posts: 1,883	You might check your grounds, the battery cable ground, the engine to cab ground, and the cab to frame ground. Bad grounds will do some crazy stuff, mine used to flicker the lights and shut the radio off everytime I hit a bump. __________________ 67 K-20 350, SM465, Eaton rear, 4.56 no spin option 00 Dodge 2500 4x4, 24V cummins, 5 speed Chad South Central Nebraska

01-17-2003, 09:50 AM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Based on your description, I believe that the regulator in the alternator is defective. Jim

01-17-2003, 10:44 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Even though the alt is 10 times better than a generator, it is hard to build one that can operate in the whole RMPM range that they are needed to work in (aka...650 RPM to 5500 RPM) So they designed it to not work too well at idle. At least, this is what my alt rebuilders told me. I find it to be normal with older vehicles. You can speed up the alt by installing a smaller pully on it, or a larger one on the crankshaft...the oposite of an underdrive set up.



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