I have a 2000 Dodge Ram 1500 with the 5.2L engine. Yesterday morning after driving about 20 miles away from home and while stopped at an intersection, I heard a high pitched whining noise from the engine compartment. After driving about 5 more miles,the Check Gauges light came on and my battery gauge pegged out at 18 volts. I pulled over and stopped and the gauge dropped back down to 14 volts. I resumed driving and a few miles later the same thing happened. This time I disconnected the alternator because I was afraid the high voltage would cook my battery and maybe damage the truck electronics and resumed driving. Of course with the alternator disconnected, the Check Gauges light stayed on, and the battery gauge read zero. The whining noise also stopped.

When I reached my destination, I plugged the alternator back up and cranked the motor up. The Check Gauges light stayed on, and the battery gauge still read zero. The alternator wasn't charging. I shut the truck back down and left it in the parking lot.

About six hours later I went back and started the truck up to head back home. Everything was back to normal, the Battery gauge read 14 volts and the Check Gauges light was off. No whining noise. I drove back home which was about 50 miles and an hours drive away. Everything was still normal. The Check Engine light never came on and there are no codes.

My question is, what is the most likely cause of this problem, the alternator or the voltage regulator in the PCM? I'm thinking that the regulator is the most likely cause, but the whining noise has me wondering if there is a problem in the alternator.

 

regulator is cooked

 

my voltage regulator did the same thing to me but no whining noise. i recommend you change the alternator and check all your grounds. I'm having a similar problem.

 

Check the wiring first. Make sure all connections are clean and tight. If that doesn't fix it, have the alternator tested. If the alt is ok, regulator is bad, which, unfortunately, is part of the PCM.....

 

SCAM ALERT. If you remove the alt and carry it to get it tested, ask them to show you the machine’s readings. Our SUV's alternator w/ an internal regulator was overcharging intermittently like that. I carried it to one of the local Adv Autos. The guy put it in the machine & then tells me it's not charging. I question it & he shows me that it’s reading 11V (even after I told him what it was doing). I smelled a rat, so I said, “Well, get me another alternator then.” When he brought it out, I insisted he test the new one and I watched him intently. Guess what…the machine read 11V. I found it interesting that he quickly discovered, pointed out, and reconnected a loose wire on his machine, and the new reman alternator began functioning properly.