1984 GMC Sierra 6.2 Needs Alternator - But Which One?

I've been putting up with my '84 Sierra's lackluster alternator performance
for a long time now. Unless driven very regularly, it would have dead
batteries. Now it doesn't even really charge them when driven or run...the
output starts out strong after starting (14.5 volts) but soon drops to 12.8
with next to no load (everything that can be turned on is turned off).

The battery connections look good at both ends, and neither battery is very
old. The drive belt is tight, so I think the alternator is sick and dying.
It is original to the truck as far as I know. I've been looking for a new
one, and the consensus at various auto parts stores is that the alternator
is rated for about ~75 amps maximum output on these trucks. This can't leave
much left over for charging both batteries when you factor in headlights,
radio, blower fan and all that stuff being turned on. It really seems like
such a "small" alternator would lead a very hard life.

However, the clerk at Advance Auto Parts showed a number of beefier choices,
going all the way up to a 140 amp rated unit. I'd tend to go for the larger
alternator...the idea being that a larger unit would be under less stress
and have more ability to take on heavy loads when they appear and while
still charging the batteries.

What I'd like to know is if I'm on the right track here--if I should spend
the extra money for the large alternator or choose something smaller (there
are a few choices between the stock unit and the higher rated ones)? Also,
would the larger unit be compatible with my truck (belt and mounting wise)?

Thanks in advance for any info, thoughts, whatever.

William

Marsh Monster wrote:
> On Jan 23, 8:53�pm, "William R. Walsh"
> <newsgrou....TakeThisOut@idontwantjunqueemail.walshcomptech.com> wrote:
>> I've been putting up with my '84 Sierra's lackluster alternator performance
>> for a long time now. Unless driven very regularly, it would have dead
>> batteries. Now it doesn't even really charge them when driven or run...the
>> output starts out strong after starting (14.5 volts) but soon drops to 12.8
>> with next to no load (everything that can be turned on is turned off).
>>
>> The battery connections look good at both ends, and neither battery is very
>> old. The drive belt is tight, so I think the alternator is sick and dying.
>> It is original to the truck as far as I know. I've been looking for a new
>> one, and the consensus at various auto parts stores is that the alternator
>> is rated for about ~75 amps maximum output on these trucks. This can't leave
>> much left over for charging both batteries when you factor in headlights,
>> radio, blower fan and all that stuff being turned on. It really seems like
>> such a "small" alternator would lead a very hard life.
>>
>> However, the clerk at Advance Auto Parts showed a number of beefier choices,
>> going all the way up to a 140 amp rated unit. I'd tend to go for the larger
>> alternator...the idea being that a larger unit would be under less stress
>> and have more ability to take on heavy loads when they appear and while
>> still charging the batteries.
>>
>> What I'd like to know is if I'm on the right track here--if I should spend
>> the extra money for the large alternator or choose something smaller (there
>> are a few choices between the stock unit and the higher rated ones)? Also,
>> would the larger unit be compatible with my truck (belt and mounting wise)?
>>
>> Thanks in advance for any info, thoughts, whatever.
>>
>> William
>
> ==========
> ==========
>
> 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.