92 Yukon voltage issues

log2 · March 2, 2017

Hello, I have a 92 yukon plow truck and I seem to be having a voltage issue, I was hoping someone would be able to clear some things up for me.

So I just changed the alternator on it to an ad244 (I'm pretty sure) so it should have a fairly high idle amperage. When the truck is running, my volt meter reads 13.4 volts with nothing on. If I turn on a my heat, on low setting, it drops to 13.1 volts. If I turn any lights on (light bar, pod lights, or even headlights) it'll drop about .3v per item.

I feel like with this alternator, even at idle, I should be getting roughly 100amps which should be enough to run almost all of my accessories without having to touch the batteries at all.

When I go to the alternator, with the truck running, I get 15 volts constantly, at the batteries I get 15 volts, but the voltmeter reads 13.4 volts. (Truck has dual batteries)

When I shut the truck off, the batteries read 12.9 volts

So question 1 would be why does the alternator put out 15 volts (which is normal) then inside the car, at the voltmeter, it shows 13.4v

question 2 is, the ad244 came with a 4 pin plug, with 2 wires coming out of it, and the alt on this car only had 1 wire, so I connected it to the same wire which was L on the plug, but am I supposed to be connecting both wires? Tutorials aren't very clear on this (at least not that I've found)

question 3, when I have the engine held at 2500 rpm, and raise the plow on it (which takes about 200 amps) and I have my light bar on, the light bar dims significantly, which it shouldn't because the batteries should have enough reserve to run it all just fine. Why would this be happening?

Thanks a lot

log2 · March 4, 2017

I had the batteries tested, and the alternator tested, they all tested fine.

I installed one battery only, and started the truck, and got 14.9v on the voltmeter, and drops to 12.5 when raising the plow, and 14.9 with the lights on. So I would assume whoever wired the second battery in, messed it up somehow. But it seems to be working fine now. It draws 170 Amps when raising the plow, and 50 amps with all the accessories on at idle. All good!