Originally Posted by Diesel_Brad

What voltage was the truck putting out while running?

Did they LOAD test the battery? Or just check voltage?

Originally Posted by Phil Woolfson

Check your wires? I recently replaced a mishmash of wires with some high end fine stranded big wire I had left from an AV install in my other car. Soldered and sealed all ends. I've had 2 grounds go up over the years.

Originally Posted by Tedster9

I'd tend to think, that if everything is otherwise OK, a stock OEM alternator should do fine. A larger alternator should not be "required", as such.

One aspect that is sometimes overlooked, as mentioned earlier, run a voltage drop test on the individual battery cables and grounding points and alternator hardware. It's simple, quick and easy, and no disconnecting anything. It's based on the fact that electricity likes to take the easy path.

So if we put a voltmeter in parallel with a wire, or connection, while under load, the voltage drop in that circuit will be displayed as a positive voltage on your DVM. Since an alternator and other high current components will be crippled with ohms resistance practically too small to measure, they are always tested under load, for voltage drop.

Just a few hundredths of an ohm resistance anywhere in the circuit will reduce alternator output by 1/3rd. Maybe not enough to notice at idle, but apply any sort of load, and it will not be able to keep up.

Because of this phenomenon I bet a lot of alternators are replaced unnecessarily. It's not that bigger alternators ain't better but it makes more sense to get the performance we already paid for, instead of heating up wire and spending even more on replacement alternators. Worth checking out anyway.

Originally Posted by tjc transport

what year truck? on my 88 to 91 trucks, i had to whomp on the top of the dash to get the volt gauge reading properly. all 6 of them were like that.
the needle in the gauge was slightly bent and would rub against the gauge face when it was low voltage or the key was shut off.

Originally Posted by choate

What's up everyone. Haven't posted in a while which has meant no issues w the truck lol. Well today the battery gauge continued to go lower and lower. I had the batt, alt and starter checked. The diagnostic tool said the batt need replaced even thought it read like 12.8 volts. What's weird is the batt indicator on the dash continued to go down which to me would indicate a problem with the alt (charging). Battery is from 09 so I'm gonna replace that and see if it helps but is it possible the gauge connection itself is bad or something?

Originally Posted by choate

The positive cable does have some corrosion on it but not enough to cause any issues i wouldn't think. Plus the fact the volt meter looks good until the fan kicks on makes me think that the cable isn't the issue but I'm gonna let a local good shop look it over