Engine/Transmission (1998.5 - 2002) Is my voltage regulator broken?

[AC]

Wife was driving the truck back from the mountains the other day and the Check Gauges light came on. She said the voltmeter had dropped way down. Later the Air Bag light came on and then the radio shut itself off.

I pulled the alternator out and took it in and had them bench test it. They ( NAPA) told me it was TU and sold me a replacement. Since I have installed it the voltmeter is back up to about 12. 5 but that's about it. Before this happened the gauge would always read about 14. I know the regulator is in the PCM and am wondering how to check things with a voltmeter to find out what's going on. I have a big trip in a couple of days and don't want to be stuck.



Thanks, AC

 

[AKAMAC]

What condition are your batteries in? It sounds like one has a dead cell. Mike

 

[AC]

My batteries are only a year or two old but in the short time she drove it home I think the batteries were drawn down pretty hard. We had the camper on and the refrigerator was running on DC and that can put a pretty good thump on a battery in no time. I had the trickle charger hooked up over night and I'm doing it again tonight but it didn't seem to be help much yesterday. The truck started right up though in the morning and again on my way home. I just hate looking at that gauge and seeing the voltage barely hanging on.



AC

 

[Supermod56]

You need to fully charge the batteries before you test the charging system, a bad/low batt will show up as low voltage on the voltmeter or a bad regulator. Charge em and put a voltmeter on it while it's running, should be around 13. 8-14. 5 volts.



Tom

 

[AC]

Do I just check from the + to - on the battery or do I need to go from the B+ on the back of the alternator to a ground? AC

 

[Supermod56]

I just put it on the battery terminals while it's running, that should tell you what is going on. If that is low, check it at the alternator. It's imperative that you have a good charge on the batteries with a regular size charger, a lot of alternators/regulators have been changed due to a bad batt. At the shop I used to work at, the rule was to install a known "good" batt before we checked anything.

 

[AC]

I took it to Les Schwab and had them check the system and the batteries checked out fine but the alternator didn't. The tech told me that he had to go through 8 alternators before he found a good one for his jeep! I went back to NAPA and pulled the rebuilt one out and had them check it and sure enough it was bad. This time I had them check the replacement on the bench BEFORE I installed it. All is working now!

AC

 

[Supermod56]

Yep, I have numerous ones that were no good!! I would think for what they cost they would work occassionally!!!!



Tom