Volt gauge ?

[555_triple_nickel]

hey,
has anybody had the volt gauge die on them ? my original volt gauge was reading low, so i had napa test the alternator and it was bad. i replaced it with the OEM one (with warranty) as well as the voltage regulator and put in a new interstate battery. The truck still runs but the gauge still reads low. any ideas before it goes to the shop ?

[1990]

What year is your truck? The Voltage reg might be done. It could cause the alt. to not charge.

External Voltage Regulator for 92-93 models
http://www.dieseltruckresource.com/faq/ ... lynewfaq=1

[Tacoclaw]

Before you get in too deep, start the truck and check your voltage across the battery terminals with a multimeter.

My friends 91 model truck's volt meter also reads at what I assume to be the 12v position, which is where my gauge sits when my engine isn't running. His truck has been like this since he's owned it, but has started every day and never failed.

[555_triple_nickel]

i did replace the volt regulator and that didn't fix it. it wouldn't bother me but for the longest time it worked fine, but it just randomly died as i was driving home from work. its a '91 so idk if that helps

[1990]

Did you get a good VR? The cheap ones will not last. I had one fry as soon i started the truck.

[555_triple_nickel]

I just got the 14 dollar one from Napa

[Tacoclaw]

Before you get in too deep, start the truck and check your voltage across the battery terminals with a multimeter.

Did you ever do this? If you're getting 14ish volts across your terminals when idling, then your VR is fine. It could be a bad dashboard ground or something making your gauge read funny, you won't know until you check what your charging voltage actually is.

There's no use throwing $$ at something if you haven't checked the basics, especially electrical stuff.

[555_triple_nickel]

thanks ! i get 12 volts across the terminals at an idle. so now what ?

[Tacoclaw]

EDIT:Since you're there anyways, bump your throttle up a bit and see if it starts charging. That would be the fastest easiest thing to do first. My needle drops down if my truck goes below it's normal idle point.

I'd say the first thing to check is the regulator ground. It grounds through it's own body, so make sure it's mounting holes in the firewall aren't rusty or anything, and smear some Nev-R-seize in the bolts before you put them back in. EDIT: also, check the blue wire going into the regulator for key-on power:

Then check the fusible link itself for the alternator. It's the black one that's a good bit bigger than the others. Just bend it around and see of it feels like there's no wire inside of it. Next, check where the fusible link charge wie where it exits the alternator. There is a connector near it that may have come apart.

If you're feeling particularly brave, there should be 3 wires going into your alternator. The bigger, black charge wire, a small blue wire, and a green wire.(the 4th black wire going to the front of the engine is just a ground for the alternator case) If this is the case, test the blue wire to make sure it's getting key-on power. If so, I THINK that grounding the green wire will make the alternator go full-charge. You can try this, at your own risk, to make sure the alternator is actually good. Don't do it any longer than needed to get a voltage reading at the battery, as doing it too long could ruin/cook/explode the battery.

I may have missed some easy checks, since I'm doing this at work , but I guess after that you could take the battery and alternator and have them tested. It is possible they were bad when new. If nothing else, another VR could be put on, but 1990 is right. The cheaper ones have never done me any good.

Another Edit: Never unplug/plug in the VR while the key is on or the engine is running. It's supposedly bad for them, and may ruin it.

I'll edit if I think of anything else, and encourage anyone else to correct anything I may have wrong.