Ok, so I've had this problem intermittently for the past few months, but it's become more common these days, so I figured I better do something about it. What the problem is is this: sometimes, when driving, the speedometer will begin bouncing eratically. I can usually flick my brights on and off, and it will fix the problem, sometimes not though. When this is going on, the voltmeter is showing around 16 volts, sometimes higher. Other times, I will notice the voltage drop down to like 10 volts, accompanied by dim headlights, particularly the driver side one, and dashlights coming on dimly, mainly the left turn signal, wait to start and one other, I can't remember which.

Also, there seem to be 2 circumstances which generally correlate with this electrical activity. One: the headlights are on, and Two: I have been driving on some less than smooth roads (pastures and the like).

I think it's either the voltage regulator going bad, in which case I would switch to external regulation, or that I have one/many bad grounds. What does it sound like to you?

Thanks for any help,
Cal

 

The ground's are free I would check them first. You also might want to have the charging system checked to make sure it is charging properly.

 

mine with similar speedo problem turned out to be a worn-out ratio drive, which I'm still trying to find a replacement for. it's a late '93 350 "tweener" with mechanical tranny output then converted to electronic via ratio drive and electronic adapter. could you have similar problem in addition to the charging glitches? the current fix is to connect the electronic adapter direct to the tranny output but without the ratio drive the needle reads a third faster than my road speed

 

It may be something so simple as a ground issue; but, the fact that the voltage sometimes goes over 14 or so leads me to believe that the problem lies within the voltage-regulator.

Bad grounds can cause a drop in voltage, but I don't see them causing a spike.

 

Possibly the voltage regulator intermittently loosing its grounding path to the alternator. Fifteen cents worth of harness wire saved by Chrysler engineering now causing headaches for us today.

 

When I took the connection off the VR and dremel-brushed the insides of the old dirty connectors it made a huge difference in needle shake and associated pulsing...even beefing up all my grounds didn't make as big of a difference..

 

That happened too me all the time where the lights would get really bright then dim. It was the voltage regulator and battery. I put a ground wire on the voltage regulator to the body. Check your battery too, if its been charging really high volts you can weld a cell together "that happened too me". I don't know if this is exactly the problem but its worth a try.

 

I finally had time this week besides work and classes to start peeking around under there. It appears the clamp on my negative battery terminal had rattled itself loose. I tightened it and took it for a quick test drive around the yard and the voltage never waivered. I messed with my lights, brights etc., and it seems to be working properly. I'll keep yall updated.

Thanks for everyones help,
Cal