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

cliffsta · 05-17-2005, 10:18 PM

OK please enlighten me.

Doesn't an alternator provide constant juice to the electrical system? My dad said he thought it just gave juice to the battery or whatnot when the volts dropped off, and otherwise the volts would go down until the draw was great enough to warrant its juice.

The reason i ask is because sometimes, my volts start dropping off, fall below normal, even dip below 13, and i rev it up and it has no effect on the volts, then all of a sudden the volts start going back up. is that a bad alternator, or is that how it functions? Bad connection maybe? where would that be if that's the case?

thaniks,
cliff

Russell · 05-17-2005, 10:37 PM

Sounds like a bad connection to me.

An alternator will provide 14.6 volts by itself, you can take the battery right out of the truck, and it will continue to run off the alternator. My truck would occasionally do that as well, and it'd always be an issue with the the connection on the starter, came loose all the time.

piecesparts · 05-17-2005, 10:43 PM

The alternator is your source of power to the engine, truck and the battery. It will carry the vehicle without the battery. If you are seeing the voltage drop and then jump up all of a sudden, then your voltage regulator is not working well. If you have a truck that has the alternator with the internal regulator, then the diodes are not working well and it needs to be replaced. The older trucks had an external regulator and it could be sticking (mechanical design). The voltage should be read at the battery by a volt meter of 13.5 volts to 15 volts depending on the load on the truck. A voltage of 14.5 is desired to keep all working and the battery charged. You could also have a bad cell on your battery that may be causing the alternator/regulator to be confused. I recommend that you have the voltage output checked and then have the battery LOAD tested to see if it is good.

hotrodhomi · 05-18-2005, 12:59 AM

I wouldn't count out the less than precision instrument in your dash. They’re not the best either.

piecesparts · 05-18-2005, 07:48 AM

A hand held volt meter is a good thing.

cliffsta · 05-18-2005, 05:46 PM

Nah, the gauge is accurate. I shall check all the connections, that's kinda what i thought it would be, but i'm just an idiot.

05-17-2005, 10:18 PM	#1
cliffsta Stepsides RULE Join Date: Jul 2004 Location: Pineville, LA Posts: 1,921	Alternator function question OK please enlighten me. Doesn't an alternator provide constant juice to the electrical system? My dad said he thought it just gave juice to the battery or whatnot when the volts dropped off, and otherwise the volts would go down until the draw was great enough to warrant its juice. The reason i ask is because sometimes, my volts start dropping off, fall below normal, even dip below 13, and i rev it up and it has no effect on the volts, then all of a sudden the volts start going back up. is that a bad alternator, or is that how it functions? Bad connection maybe? where would that be if that's the case? thaniks, cliff __________________ 1981 Chevy C10 Custom Deluxe Stepside 350 V8, headers, side exhausts, 3-speed auto SOLD 1980 Chevy C10 Custum Deluxe Stepside 305 V8, Edelbrock Performer Intake, Edelbrock 1406 600CFM 4-barrel, TH350C. Bent rod. SOLD 1984 GMC Sierra Classic Longbed 6.2L Diesel SOLD 2009 Kawasaki KLX-250S too many mods for this signature 1999 Honda Accord EX 4-cylinder, 17" Motegi Wheels 215/45/17 Sumitomo tires, Tein S-Tech lowering springs, KYB GR2 shocks, Acura TL 20mm rear swaybar, debadged, blackhoused headlights, Short-Ram Intake Cardomain of the Accord

05-17-2005, 10:37 PM	#2
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Sounds like a bad connection to me. An alternator will provide 14.6 volts by itself, you can take the battery right out of the truck, and it will continue to run off the alternator. My truck would occasionally do that as well, and it'd always be an issue with the the connection on the starter, came loose all the time. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

05-18-2005, 12:59 AM	#4
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	I wouldn't count out the less than precision instrument in your dash. They’re not the best either. Last edited by hotrodhomi; 05-18-2005 at 12:59 AM.

05-18-2005, 05:46 PM	#6
cliffsta Stepsides RULE Join Date: Jul 2004 Location: Pineville, LA Posts: 1,921	Nah, the gauge is accurate. I shall check all the connections, that's kinda what i thought it would be, but i'm just an idiot. __________________ 1981 Chevy C10 Custom Deluxe Stepside 350 V8, headers, side exhausts, 3-speed auto SOLD 1980 Chevy C10 Custum Deluxe Stepside 305 V8, Edelbrock Performer Intake, Edelbrock 1406 600CFM 4-barrel, TH350C. Bent rod. SOLD 1984 GMC Sierra Classic Longbed 6.2L Diesel SOLD 2009 Kawasaki KLX-250S too many mods for this signature 1999 Honda Accord EX 4-cylinder, 17" Motegi Wheels 215/45/17 Sumitomo tires, Tein S-Tech lowering springs, KYB GR2 shocks, Acura TL 20mm rear swaybar, debadged, blackhoused headlights, Short-Ram Intake Cardomain of the Accord

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05-17-2005, 10:43 PM	#3
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	The alternator is your source of power to the engine, truck and the battery. It will carry the vehicle without the battery. If you are seeing the voltage drop and then jump up all of a sudden, then your voltage regulator is not working well. If you have a truck that has the alternator with the internal regulator, then the diodes are not working well and it needs to be replaced. The older trucks had an external regulator and it could be sticking (mechanical design). The voltage should be read at the battery by a volt meter of 13.5 volts to 15 volts depending on the load on the truck. A voltage of 14.5 is desired to keep all working and the battery charged. You could also have a bad cell on your battery that may be causing the alternator/regulator to be confused. I recommend that you have the voltage output checked and then have the battery LOAD tested to see if it is good.

05-18-2005, 07:48 AM	#5
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	A hand held volt meter is a good thing.



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