1984 GMC Sierra 6.2 Needs Alternator - But Which One?

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Willy............. you looked so lonely sit'n on the board with NO ONE reply'n..........so.........

:)

anywhooooooo..........

Sounds like the thing does ok as long as it's being driven. (?) Sounds like it's causing the problem after sitting for a day or so. (?)

Sounds........like you should check for an amperage draw BEFORE you go buying any new altenator dude.

The output should be around 14.2 or a little better on initial startup, with the voltage dropping back to 12.8 or so shortly after if you don't have any, many, acessories running. That's normal op. I know you well enough to realize you prob know that......

We've had a couple trucks outta the shop FLEET recently doing the EXACT same thing....amperage draw on various circuits has been the culprit so far.

Anywhooo..........i'd ck that first.

Could be the Alt is working. Could be the electrolyte has accumulated on the plates. Could be a current draw when sitting.

jest some guess's..........

anywhooooooo........... Who'd you piss off...so no one wanted to talk to you??

:)

~:~ MarshMonster ~takes a toke......pours one fer WillyWalsh the WashRack man~ ~:~

Something looked familiar abotu this post. Then I looked at the poster . . .

Nuf said.

From anyone else I would guess a typo. From you, showing off your ignorance.

SULFATE from electrolyte is accumulating on the plates.

Take the batteries in and have them checked first. I suspect that one of the batteries is not in the best condition. When you disconnect the batteries check the resistance between the leads. There should be very high resistance. If the needle moves very much then you have an short somewhere. Disconnect a fuse at a time and find out which one is shorted out. Then find the direct culprit.

Mike D.

This is backwards... Charging voltage will be a bit low after initial start up as the alternator works to replenish the battery after a large amperage draw from the starter, the voltage will slowly ramp up as less current is used to recharge the battery. Delco alternators -do- have temperature compensating circuitry, charging voltage will tend to be higher in cold weather conditions and lower in hot weather conditions.

Naturally, any accessory load from the truck will raise amperage and lower voltage.

The voltage shouldn't go under 12.8 when the alternator is being loaded at its maximum output rating.

Never seen it this way. Always has been higher initially, then dropping.

You need to go out tomorrow and connect the carbon pile across the battery, amp meter to the alternator output and a volt meter to the battery. Take an open circuit voltage reading from the battery. Start the engine and maintain 2000 RPM, note volt meter reading. While maintaining 2000 RPM engine speed adjust the load across the battery with the carbon pile until the amp meter reads near maximum alternator output rating, does the volt meter read higher or lower than the no load voltage? If you adjust the carbon pile for less amperage output from the alternator, does the voltage reading go up or down?

I suspect what you and Marsh are seeing is the effect of tapering off the engine speed from a cold start.

Hi!

I don't know. I did find out recently that if I bring them up with an external battery charger, they will stay up.

I'll do the resistance check you suggest. I'm also going to pull the alternator and have it tested to see what happens. It seems weird that it drops down to 12.8 volts with nothing happening and even less when loaded. Revving the engine up doesn't help, and I don't really know exactly where

2,000 RPM is. I'm also not sure how you'd hook a tachometer up to a Diesel engine. The ones I have are electronic and actually hook up to an ignition coil on a gasoline engine.

The alternator's behavior strikes me as weird. I have a number of other GM vehicles and not a one of them ever drops much below 13.5 volts output, even when fully loaded.

I don't have a carbon pile, so I can't make any of the tests you suggested.

William

The alternator should be able to do that also.

Good idea.

Nothing weird about it, that's what dead alternators do.

2000 RPM can be guesstimated.

There are a number of ways to measure RPM, a photo tachometer, thru the alternator or by connecting a magnetic tach pick up in the holder above the harmonic balancer.

Nothing weird about it, 12.8 volts and dropping is a dead alternator. And when I say dead alternator, that doesn't automatically mean the component itself is bad, you still need to verify the associated circuits to it.

Have you tried full fielding it? Have you checked for battery voltage at the output stud on the back of the alternator and at the red wire in the plastic 2 wire connector? Is their voltage at the brown wire with the key on?

=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D On Jan 25, 10:52=EF=BF=BDpm, "William R. Walsh" . It seems weird that it

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WILLY !!!!!!!!!!!!

=2E.........you omitted that from your original post!

Yank the Altenator and carry it in to have it checked.

Carry yer credit card with you. Like Cuda said....symptoms of a bad altenator.

~:~ marsh ~takes a toke.......goes back up to exhale in Dobony's face~ ~:~

t'n on the board with NO ONE

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yeah....yeah.........yeah...........

like yer the FIRST one to EVER point that out to me.

:)

~:~ marsh ~takes a toke.....exhales in Dobony's direction.........who said 2nd hand smoke was bad for you~ ~:~

And still refuses to learn.

So you admit you are too stubborn to learn.

Typical ignorant bully.

I see this guy is up to old tricks and passing bad info. Battery charge does not determine voltage of charge, only amperage rate. Regulator will hold voltage constant within limits of output abilty of alt. If voltage climbs when charged it is a sign of a weak alternator or bad regulator because voltage should be contastant or tend to decreases as underhood temps rise, not increase. SnoMan

Let the Trolls desend as their egos and insecurities need to be feed....

----------------- TheSnoMan.com

[snip]

Yes you are. Lets remind everyone why YOU left for a few months. ___________________________________________________________ SBJ: 4T65E

(Confuses a 4T65e with a 4L65e and won't admit it.)___________________________________________________________SBJ: Dumb brake question (Discribes the wrong brakes and won't admit it.)___________________________________________________________SBJ: Front wheel bearings-2000 Blazer?? (Claims torque specs are wrong when they are not.)___________________________________________________________SBJ: Snoball Defense System v1.01 (Snoball breaks these out when he knows he's wrong and doesn't want to admit it.)___________________________________________________________Snoman these are things YOU wrote.Don't like what YOU wrote?Then YOU should stop posting.

it's back.......

Should we point out to it that its signature field is grammatically flawed or should we keep laughing at it? I mean it kinda highlights the incompetents of the troll nicely. Then again if we do point it out, it will never be corrected...

Good thing you were able to come by 4 weeks later and straighten that out... ...the OP might have froze to death otherwise.

"need to be feed?"

What 2 year old wrote that for you?