Erratic Ammeter

[46Ply]

From cold start  ammeter sits pegged to the left.  After 3 to 5 miles it jumps clear to the right and pegs.  Then eventually it comes back to about the 3/4 mark and sits there and bounces.  

 

How would this be diagnosed properly?  

[busycoupe]

It sounds like a sticking regulator. When you first start the car and the meter is pegged on discharge, try rapping the regulator with something like a screwdriver handle. If the meter jumps to charge you have found the culprit.

Another possibility is a loose fan belt. Check the belt tension.

[Ulu]

I also had this jumpy ammeter thing happen when the ground wire on the battery came loose while driving.

 

...but yours sounds like a sticky regulator alright.

[46Ply]

Thanks guys,  I'll report back as soon as we try it.  (tap regulator)  

I just replaced both battery cables and the battery.  Had some heavy duty cables made up to proper length.  I'm sure they're good.

[Ulu]

You might actually take the cover off the regulator & look inside to see how rusty it is.

 

Remove the battery ground strap first so you don't short the innards with the cover.

 

Running a clean dollar bill through the regulator points can help clean off what's making them sticky, if the points are not too burned/pitted/corroded.

 

If you file them square, they will be clean & not stick, but the regulator adjustment will be thrown off.

 

(Before deciding to file regulator points, read the adjustment procedure in the manual. You may decide against it.)

[46Ply]

You might actually take the cover off the regulator & look inside to see how rusty it is.

 

Remove the battery ground strap first so you don't short the innards with the cover.

 

Running a clean dollar bill through the regulator points can help clean off what's making them sticky, if the points are not too burned/pitted/corroded.

 

If you file them square, they will be clean & not stick, but the regulator adjustment will be thrown off.

 

(Before deciding to file regulator points, read the adjustment procedure in the manual. You may decide against it.)

Good advice,  thanks!   Actually, I was considering taking the cover off.  But didn't think to disconnect battery, or not being a little more aggressive about cleaning the points.