Alternator or Battery

firecadet613 · November 15, 2003

Voltage is at 14amps all the time, except when I'm idling at a traffic light, with the turn signal on. Voltage will drop a little until I step on the gas and it will be fine. Sounds to me like my alternator output is low at idle, does that sound right? Alternator is a reman AC Delco, put on before I got the truck at 79k miles, currently at 112k miles

Shotgun · November 15, 2003

So what is the problem? Are you having any trouble? Your fine with anything over 12 volts.

firecadet613 · November 15, 2003

The lights dim with the turn signal blinking....

Shotgun · November 15, 2003

ahhhh....well I always use the old remove the + cable from the battery test...If truck still runs with battery disconnected alt is good and most likley a battery problem.

chevroletmb · November 15, 2003

ahhhh....well I always use the old remove the + cable from the battery test...If truck still runs with battery disconnected alt is good and most likley a battery problem.

i wouldn't recommend that test on any computer controled vehicle. just i little voltage spike can kill a computer and or seriously shorten it's life span

Shotgun · November 15, 2003

it won't hurt a d**n thing bro....techs still do the same thing when the analizer is busy

Wingnut · November 16, 2003

Nope, wont hurt a thing.

As to your problem, on my trucks, the thing that has gone first is the battery cable itself. It looks fine on the outside, so there is no way to tell just by looking at it.

Battery cable is cheaper than an alternator, or a battery too.

Just my .02

chevroletmb · November 16, 2003

i'm just currious if you guys know anything about electronics?

and just because you've seen technition do doesn't mean it's the right way to do it

Shotgun · November 16, 2003

I know plenty about electronics .It's what I do for a living EE

chevroletmb · November 16, 2003

then maybe you can explain why and how a voltage spike won't hurt delicate

computer components like stated on this link?

http://www.forparts.com/techbattery.htm

Shotgun · November 16, 2003

I posed this question to my neighbor (a GMC Dealer Service Manager) and he said the only danger is if the + post would be allowed to short out to ground while the vehicle is running. He also stated that he knows of no instances where this so call damaging spike has occured.It may bother some of those imports on that site you posted but we are talking GM here right? GM regulators have blocking diodes that prevent current from traveling in the wrong direction and MOV's (Metal Oxide varistors) for preventing cross current spikes.

chevroletmb · November 16, 2003

well this is gm so i guess if you want to take the risk go right ahead

but you won't ever see me trying it.

Document ID# 173237

2000 GMC Truck GMC K Pickup - 4WD

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Ignition OFF When Disconnecting Battery Notice

Notice

Always turn the ignition OFF when connecting or disconnecting battery cables, battery chargers, or jumper cables. Failing to do so may damage the Powertrain Control Module (PCM) or other electronic components.

--------------------------------------------------------------------------------

Document ID# 173237

2000 GMC Truck GMC K Pickup - 4WD

studly · November 16, 2003

When I was younger, a buddy was goofing around and pulled the

battery cable off of my Dodge Dart. The headlights flashed a

few times and were glowing like black lights (ultraviolet lights).

Seriously!

I would never pull the battery cable off of a running vehicle.

Voltage regulators without a load are unpredictable.

I'm an EE, too.

Red2500HD · December 29, 2003

well this is gm so i guess if you want to take the risk go right ahead
but you won't ever see me trying it.

I guess that is your choice, but why, then, did you ask for other opinions?