Alternator running hot

[stachcold]

A little while back I replaced my battery because it wouldn't hold a charge anymore. While I was doing that I decided to replace the battery cables while I was at it. It wasn't long after that my alternator had a melt down (the wires going to it melted). I had the alternator tested and it passed but I decided to change it anyways to go to a internally regulated alternator because my external voltage regulator was looking pretty rough. The guy at AutoZone talked me into getting a one wire alternator. I hooked it up following the proper internal regulator setup and everything ran fine, but when I happened to touch the alternator it was really hot. Everything else in the engine bay was only warm to the touch. I went back and checked that everything was hooked up right and it looks like it is. After everything cooled down I started it up again to see if it would happen again. After only a minute or so the alternator started to heat up again? Everything ran fine before I replace the whole battery system. Any idea's what the problem could be?

[oldgold70c10]

Double check the connections between the battery, alternator, and the rest of the electric system. Check for poor grounds, too. If the alternator case ground to the engine isn't good, it will trick the regulator into passing more current because it will read the voltage as low. If you have an amp gauge, you can also check to se if the alternator is constantly trying to over charge by watching if the hand drops back to the center a few minutes after start-up when fast idling.

[drman929]

stachcold, I'm going to ask a quick question in your thread if you don't mind...it does pertain to the same subject though.

oldgold, right when I start my truck the amp gauge needle is around the 3/4 position, but after about 5 seconds it returns to the middle and stays there if the truck is running or not. I'm putting out around 14 at the battery per my electrical tester. What will overcharging harm?

[truckdude239]

14 volts is perfect drman anything higher then 15 will sort out headlights and stuff like that please remnebr next time no to hijack posts

[mnunn454]

Sounds to me like the new single wire alternator's alternator's either bad, or it's not hooked up right. No way should it be getting as hot as you say. Try running the output through a decent ammeter while measuring its voltage.

[oldgold70c10]

Originally Posted by drman929

stachcold, I'm going to ask a quick question in your thread if you don't mind...it does pertain to the same subject though.

oldgold, right when I start my truck the amp gauge needle is around the 3/4 position, but after about 5 seconds it returns to the middle and stays there if the truck is running or not. I'm putting out around 14 at the battery per my electrical tester. What will overcharging harm?

Middle should be normal, that jump to the 3/4 position is the regulator in the alternator kicking out more to recharge the battery after cranking. It is perfectly normal, and of no harm since the battery will suck-up the extra currnet being produced to return to full charge.

Another way to make sure the regulator is responding to your truck's electrical needs is when you switch high-current stuff on and off, such as the headlights. Watch the amp guage, there should be a slight lag, since the regulator's response is not instant. When you turn them on, the hand should move to the left slightly and then recover back to the middle. Likewise, when you turn the lights off, it should move to the right slightly, then recover to the middle.

If it doesn't respond, the either the guage is wired wrong or inoperative, or, the regulator in the alternator is bad. Most likely cause of the alternator getting hot would be a bad regulator or connection to the regulator.