Alternator not charging at idle
 

My battery went dead on me a couple of times lately. My alternator light comes on at idle and doesn't go away until I rev it up quite a bit. I checked the voltage on the battery and it goes up to about 13.5 volts while I'm reving the engine so it looks like I've got a charging problem only at idle.

Here's my question: Do I have to replace the alternator or may it just be the voltage regulator? How can I check which one it is?

Thanks,

Scott

The easy/cheap way is to try replacing the voltage regulator first. That's the most likely problem, but if it doesn't fix it you will have to look at the alternator and you will still have a spare voltage regulator.

Just Did the Same Repair...
 

last weekend. Driving home one night last week I progressively lost all electrical power. It was just like Apollo 13. Fortunately, the diesel is completely mechanical so even though I was running off the battery and depleted it, the motor continued to run with no problem.

Turns out the voltage regulator that bolts onto the back of the alternator and houses the brushes, needed to be replaced due to completely worn out brushes. Ten minute job and $34 for the part. I would pull the regulator out and inspect the brushes.

I just pulled the regulator. The brushes are shot. I hope a new one will take care of the problem. Don't want to have to spend $150 on a new alternator.

Scott

Sounds like you have the problem identified. One other possibility would have been a loose drive belt.