Anyone know what the output of the alternator should be at idle with lights, ac, radio, wipers on? Mine starts at 13.8v with no accessories, with accessories on, it drops over a few minutes to 12.5v, would this be within specs or maybe my alternator is getting week. Thanks in advance for any info. its a 99 dakota 5.2 5speed SLT

 

13.8v is about right at idle. The charging voltage does vary by temperature. It will drop some at idle with a load on it, normally.

Where are you measuring the voltage?

Make sure all the cables are clean and tight on the alternator and at the battery. Are you getting any codes?

 

No codes, everything is clean and tight. I measured the voltage at the battery and at the alternator. I went ahead and put a remaned alternator on and it slowed the drop way down and held at 12.8v it was the original with 155,000 miles on it. Battery voltage was at 12.6 when started checking, I don't think it should have dropped below that unless my battery is weak as well, could be its 6 months old already and I have seen them fail within minutes of purchase, will get that checked tomorrow. I also noticed the cable from the Alt to the PDC has some build up in it, going to replace that tomorrow also and see what happens.

 

Ok took the truck to Orielly's, Battery passed, Alternator passed, so we tested it with all accessories on and there machine said voltage regulator fail, Passes with everything off. Not sure where to go from here, appreciate any help. Thank You.

 

The voltage regulator is in the PCM. Look online for a rebuilt, it's a lot cheaper than a dealer. You'll have to give them your VIN and other infomration and they'll program it for you.

 

A few years back (10) I got a remaned alternator from autozone. Came with warranty.
Had to use warranty 2 weeks later, alternator went kaput.
2 weeks later kaput again.
2 weeks later kaput again.
The 4th remaned alternator I took straight to starter shop to have rebuilt another $60.00. But it lasted until I got rid of the car. I don't get ANY electronics from Autozone now.

Would have had the original one rebuilt in the 1st place but it was stolen. Who would steal an alternator?

 

On charging just remember WAVe
Watts = Amps x Volts

 

Like Dan said the temp plays a part in charging. There is a sensor under the battery tray that tell if the battery gets too hot not to charge. May have issue there. Don't know but couldn't hurt to check.

 

See this post

https://dodgeforum.com/forum/3177360-post4.html

 

Well the only thing I can come of with is that it is the nature of the beast, with all accessories on it will drop down to 12.6 volts and hold there now, which is what the battery voltage is minus static charge, give it gas and it will run up to 13.8V-14V. Runs at 13.8V with every thing off at idle. Those testers they use at the parts store say VR fail with accessories on at idle, passes with accessories off.Should have bumped it up a couple hundred rpms and checked it then. Going to have it checked on Monday with a good scanner.