Alternator Question - Adivce please.

[partybear]

I have a 1996 Chevy 'burban K2500, 7.4

The other night I was driving home and found the lights to me dim. the ammeter was reading about 11 (it's usually at 14).

I had the alternator checked and they said it was dead.
I bought a new one and put it in.

It was charging at 14 until I got on the highway. It fell back to 10-11.

I got it back home and took the alternator back the store. = auto parts chain around Cleveland. It ends up the Don Knotts character sold me a lessor amp alternator.

I got the right one this morning, I installed it and the ammeter is still reading at 10-11.

This a remanfctrd alternator. Do you think I got a bad one or did the lessor 105 amp alternator (the one I pulled was 127 amps) do damage to my system.

Could it be a faulty ammeter reading?

As always, thanks for any advice.

- Jim

[2000CAYukon]

I assume that you are referring to a volt meter not an ammeter (since an ammeter measure current flow in amps).

Where are you reading the volts from? With the engine running, the volts at the battery should not be less than the battery (which is 12.2 volts). Ideally, at the battery, the volts should be between 13 and 15 (engine running).

You should also inspect all the battery cables for good tight and clean connections, including the alternator to battery wire.

How do the lights look with the current alternator?

EDIT: A lessor amp alternator should not have hurt anything especially for the short time it was installed.

//2000CAYukon

[777stickman]

Voltage readings for a properly running alternator should be 14.2 to 14.7 volts. This should be read between the positive and negative battery posts. I went through 3 alternators from NAPA on the '78 Blazer before they finally got one right????? Anyway you need to check the voltage coming into the battery from the alt to be sure. Also like 2000 says, check the connections at the battery for corrosion,etc......Steve

[Elbert]

only real way to check alternator is to get a digital multimeter (sears, radio-shack) have some decent cheap ones that do the job... Truck running check the voltage at idle at the battery. You should see something around 13.0 to 14.0 volts. The alternator has to put out over 12 volts to charge the battery.
Many of the generic alternators are crap. If you see anything under 13.0 volts the alternator is bad. I think advantage and autozone have some ok alternators with life-time guarantees. My truck seems to eat an alternator aobut every two years...I've normally been getting them rebuilt (local guy ) but at $85 a pop I could have bought a life-time unit and in the long run would have saved money. The best quality alternators come from the OEM...then in the used market if you have a person who knows how to rebuild them and then finally the ones you buy at the local parts store (my view).

[jsnowbordr47]

Yeah, check for corrosion on your battery cables and terminals, this creates resistance which affects charging sometimes. A properly charging/running car battery should read from 13.6-14.6 on a digital voltometer (anything higher can kill your battery). Also are you running any accessories when it reads low, On mine the battery meter dips down when I have both the front and back fans on full blast.

Good Luck