🚀 go-pugleaf

>    I have a '69 Plymouth Belvedere.  The voltage has been high
> since I bought it. (About 16-18 volts)
> 
>    Finally the battery died from overcharging.  I replaced the battery and
> had the electrical system checked.  I was told I had a bad alternator. I
> replaced the alternator, as well as the voltage regulator, for good
> measure.  The voltage was down to about 13-14 volts for 5 minutes, then
> back up.
> 
>    I took everything back to a local automotive electrical shop (ACE) and
> was told the new regulator was just fine, but my new voltage regulator was
> bad.  I replaced the voltage regulator (again) and the same thing
> happened.  I worked all right for about 5 minutes, then the voltage
> rose to 17-18 volts.

One of my two '61 Valiants had a similar problem for years - it used to eat
*at least* one voltage regulator per year, and it wasn't exactly gentle to
batteries either!

Since you seem to have already pretty much confirmed that the obvious parts
of the electrical system (alternator, regulator and battery) are OK, there
are a couple of less obvious things that you might want to check out.

First of all, disconnect the hot lead at the regulator and use your VOM to
check the voltage at that point.  If it is significantly lower than the
voltage at the battery, then whatever is causing the voltage drop is probably
the culprit.  Unfortunately, finding the source of the resistance may be
difficult, but the ignition switch would be one thing to check.

Secondly, check to see if your regulator is well grounded.  If it's typical
of how Chrysler used to do their regulators, it will be grounded through
its base to the chassis, so check for corosion there.  Also check for missing/
lose ground straps from engine to chassis and the like.  The easiest way to
check may be to run a wire from the negative pole of the battery to the
base of the regulator and see if the problem goes away.

A factory shop manual can give you more exact testing procedures and
what voltage drops would be acceptable in both cases.  In my case I found
that I had both a bad ground *and* a bad ignition switch, and I have had
no further problems since correcting them.

Good luck!