alt problem??
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Senior User
Joined: Nov 2005
Posts: 138
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From: Buchanan,MI
alt problem??
hey all its been some time!!!!
well i think its finally happened. started my truck tonight. started fine but batt light is on and alt gauge is reading low. Gauge comes up from about 9 volts to about 11 volts after glow plug relay kicks off.
My question is which one? the top one seems noisy and slight squeal when coming down to idle after quick rev. i hope its this one($150) and not the bottom one($240). no access to tester w/o taking off. How do i check with volt meter? Looks easy enough to change.....
please help. i am supposed to leave for snowmobile trip in 3 days.
2000 f350 7.3 dually stick 4:10 gears 4x4 217,000 miles
well i think its finally happened. started my truck tonight. started fine but batt light is on and alt gauge is reading low. Gauge comes up from about 9 volts to about 11 volts after glow plug relay kicks off.
My question is which one? the top one seems noisy and slight squeal when coming down to idle after quick rev. i hope its this one($150) and not the bottom one($240). no access to tester w/o taking off. How do i check with volt meter? Looks easy enough to change.....
please help. i am supposed to leave for snowmobile trip in 3 days.
2000 f350 7.3 dually stick 4:10 gears 4x4 217,000 miles
Post Fiend
Joined: Mar 2007
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From: Texas
Which one? Do you have dual alternators? Autozone was able to check my alt without pulling it from the truck.
I believe if you touch the big wire off the back of the alt. with a multi meter you should see around 14 volts if it's good.
I believe if you touch the big wire off the back of the alt. with a multi meter you should see around 14 volts if it's good.
Senior User
Joined: Jul 2006
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From: Florence,SC
Use a multimeter as was previously stated above, red lead to hot terminal on back side of alternator and black lead to a ground somewhere. You can check each alternator independently and find the bad one.
P.S. I'm not as familiar with the schematics of the dual system as some of these guys, but I believe this should give you a very valid result.
P.S. I'm not as familiar with the schematics of the dual system as some of these guys, but I believe this should give you a very valid result.
Post Fiend
Joined: Mar 2007
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From: Texas
Originally Posted by cwt580
yes duals.....acts like the one that runs GP's battery. is that the top one???
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Senior User
Joined: Nov 2005
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From: Buchanan,MI
glows are working fine. because it started at 20 degrees not plugged in. light comes on after it starts before GP's quit running. interior lights are dim until GP's click off. then volt s gauge and lights come up slightly but still not fully. "idiot light" never turns off!!!
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Post Fiend
Joined: Mar 2007
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From: Texas
Then assuming your batteries are good (I don't think I've ever seen a battery light for bad batteries) then I'd say one or both the alternators are bad. I have no idea which one. I also have no idea if it would be a good idea to replace both at the same time.
Can you check voltage off the back of the alt's?
Maybe someone else with duals will chime in with some knowledge.
Can you check voltage off the back of the alt's?
Maybe someone else with duals will chime in with some knowledge.
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Joined: Sep 2004
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From: Carroll County, MD
As much as I hate to say this, it might be both alt's. Here is my thinking:
With the truck just running in the driveway after starting, and nothing much running, either alternator would put out more then enough juice to keep everything up to voltage. Just ask all of us with only 1 alt. That being the case (low voltage) would require that both alt's have failed for your voltage to be low. Sorry
With the truck just running in the driveway after starting, and nothing much running, either alternator would put out more then enough juice to keep everything up to voltage. Just ask all of us with only 1 alt. That being the case (low voltage) would require that both alt's have failed for your voltage to be low. Sorry
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Senior User
Joined: Nov 2005
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From: Buchanan,MI
what really sucks is....snow and cold and a garage not big enough to pull it in!!!!!!
why would you think both alts at the same?
dash volt meter reads about 11-12 volts when gp's stop. normally about 13-14 volts when running. batt light never shuts off.
just dont see both alts going at the same exact time........top one is making some noise now that ive never heard before tonight. why the difference in price? they must do some different functions or why the need for both?
why would you think both alts at the same?
dash volt meter reads about 11-12 volts when gp's stop. normally about 13-14 volts when running. batt light never shuts off.
just dont see both alts going at the same exact time........top one is making some noise now that ive never heard before tonight. why the difference in price? they must do some different functions or why the need for both?
Last edited by cwt580; Jan 15, 2008 at 09:40 PM.
Senior User
Joined: Sep 2004
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From: Carroll County, MD
Not that both went at the same time, but that one has been dead for a while, and the other just died. Have you ever put an alt on it before? My '00 has had a few, they don't last forever.
Like I said, each alt has the juice to keep the system up to voltage by itself, so it would be really tough to tell just by voltage if one alt failed.
Like I said, each alt has the juice to keep the system up to voltage by itself, so it would be really tough to tell just by voltage if one alt failed.
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Senior User
Joined: Nov 2005
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From: Buchanan,MI
maybe just get away with the one for now. if one had bad windings,brushes,bearings wouldnt that cause a draw on the full system anyway? $400 for alternators is a little hard to swallow.
if only 1 was out would i get any battery light. Maybe both are bad but not this week folks the well is kinda dry right now....
so you say it would probably run on 1? this truck is normally a driveway queen anymore just use for trips and camping....
if only 1 was out would i get any battery light. Maybe both are bad but not this week folks the well is kinda dry right now....
so you say it would probably run on 1? this truck is normally a driveway queen anymore just use for trips and camping....