18.5 volts at the battery terminals?

[67_Eldo]

I was playing with an audio amp in my recently returned 1967 Eldorado. It would play just fine with the car sitting in the driveway with the motor not running. But if I used the amp as I drove down the road, the amp's protection circuitry would kick in frequently. Odd.

So I connected a voltmeter across the battery (directly off of the terminals), and drove down the street. Sure enough, the voltage rose as the RPMs increased. The voltage finally leveled off between 18 and 18.5 volts. Yipes!

The previous owners pulled some shenanigans with the alternator wiring that I haven't yet fully diagrammed. But it seems to me that whatever they did isn't working.

So I've got to rip out what is there and either replace the wiring with a kit that converts the 67 to an internally regulated (preferably higher-amperage) later alternator or else restore the external regulator/alternator combo that the car originally shipped with.

Do any of you have ideas or suggestions on which approach to take?

Thanks!

[Seville1957]

NOT GOOD, something is wrong with the regulator circuit. Get service manual and check all wiring!

[Jeff Rosansky CLC #28373]

Yes. If it's a points type regulator clean in between them and be sure they are free to move.
Jeff

[bcroe]

It sounds like the battery has been seriously damaged.  My opinion, converting to
a heavy internally regulated alternator and eliminating a lot of questionable stuff
is a great idea.  Bruce Roe

[Glen]

I agree the battery is probably damaged.  If you still have the mechanical regulator it might be just set too high.  Check to see if the points are stuck.  If not then try adjusting the voltage regulator to 14 volts. 
IIRC the instructions for adjusting the regulator are in the shop manual. 

[TJ Hopland]

Yes something wacky is going on there.    Original for that car would have been an alternator with an external regulator so plenty of places and chances for issues there.    I believe the cases were almost the same between the external and first gen internal regulators so maybe someone swapped some things around?    Maybe they bypassed some of the regulator circuit to try and get an internal unit to work then gave up and went back to an external but didn't correct the modifications or damage?

[bcroe]

Original for that car would have been an alternator with an external regulator so plenty of places and chances for issues there.    I believe the cases were almost the same between the external and first gen internal regulators so maybe someone swapped some things around?   

That was the case; I bolted a first gen internally regulated alt into a 63 bracket
on my 62.  I was happy to get rid of the failure modes and wiring of a mechanical
regulator, not to mention eliminate another source of radio interference.  Bruce Roe

[67_Eldo]

I don't have it put back together yet, but it looks like the problem was a broken ground wire from the alternator -- excuse me, "generator" in the shop manual -- to the external regulator.

This wire actually looked OK from a distance because the insulation was holding the wire to the eyelet that connected to the alternator. It wasn't until I started moving stuff around that I saw that it had broken in the not-recent past. That would explain why it destroyed its almost new battery right after I first bought the car.

If I get it all put back together and the voltage is still wacky, I'll report back in.

Thanks for all the advice!

[67_Eldo]

14.2 volts never looked so good! 

I replaced and resoldered all the sketchy splices that had been made in years past. (I used self-fusing silicone tape for the first time. It seems as though it will work really well.)

Put in a new voltage regulator and condenser/capacitor, just to be sure.

Cleaned up all the grounding points to insure solid connections to ground.

The cleaned up system topped out at 14.2 volts, which I can live with!

Thanks!

[bcroe]

Good work!  Bruce Roe