Voltage Regulator

[Brad0429]

First of all I am not smart when it comes to electrical components.

My car, 1968 Valiant 440 76mm single turbo, msd ignition, is suddenly not charging the battery. Battery reads 12.64v when off and about 12.9v when running with the headlights and electrical fan on. With the headlights and can on, the alternator output was about 14v. I replaced the alternator with a new spare one I had laying around, only takes 10 min, no change.

For the last 6 months or so the ammeter on the dash would bounce and pegg toward the charge side. Now it runs slightly below half on the charge side, headlights are dim, I just know it's running off the battery.

To some up the story, I took the voltage regulator apart and found one of the fusible wires melted. See photos? Could this be my issue or do I need to keep diagnosing?

 

[d55dave]

Yep. You need a new vr. The question is why it burned the wire.... are the points in it welded shut? I have had this happen.

This is a prime time to upgrade to a two field wire alternator and electronic vr. Also you should inspect the bulkhead connector and consider bypassing the ammeter. They are two common areas to fail.

 

[Brad0429]

Yep. You need a new vr. The question is why it burned the wire.... are the points in it welded shut? I have had this happen.

This is a prime time to upgrade to a two field wire alternator and electronic vr. Also you should inspect the bulkhead connector and consider bypassing the ammeter. They are two common areas to fail.

I think it may have something to do with the high output alternator I had. Things started getting funky when I installed that. I think I'm going to throw on the same one and upgrade to the electronic regulator in the spring. Thank you for your help!

 

[67Dart273]

THAT IS A FUSE...........sort of........your alternator may be drawing too much field current for the regulator to handle. Having said that, I'm sure ALL replacement regulators you buy are not solid state in a "look alike" can

Measure your field current draw. It's outlined in the service manual, and you can download several, free at MyMopar. Some of those there came from the efforts of the guys right here

MyMopar - Mopar Forums & Information - MyMopar Tools/Reference

 

[Brad0429]

THAT IS A FUSE...........sort of........your alternator may be drawing too much field current for the regulator to handle. Having said that, I'm sure ALL replacement regulators you buy are not solid state in a "look alike" can

Measure your field current draw. It's outlined in the service manual, and you can download several, free at MyMopar. Some of those there came from the efforts of the guys right here

MyMopar - Mopar Forums & Information - MyMopar Tools/Reference

Will do. I have a copy of the service manual and will check the field current. Thank you!

 

[BillGrissom]

That would be an easy repair, but I think an electronic Vreg is recommended for any electronic ignition, like your MSD box. You can get a new one for your 1968 that will bolt right up. Some are thin & chrome and others have the factory look. Check rockauto. As far as why it failed, it looks like too much current draw from the regulator. That would be the single "field" wire (grn, I recall) that runs to the alternator field (spade lug). It is probably shorted to gnd. Check w/ a multimeter, so you don't fry the new Vreg. With a turbo, and probably creative exhaust plumbing to it, your wires may well get hot. Your old mechanical Vreg uses "high-side switching", i.e. applies 12 V for "full charging" and turns off for "no charge", continuously cycling. An electronic one will give a more steady output (Kit Carlson here says it still switches on/off, but so fast you need an O-scope to view it).

 

[Murray]

In the old days we used to "repair" these by re-soldering a small wire back in place. This is a questionable practice as the wire is actually a fuse. They are known to blow for no apparent reason. Today it is better to replace the regulator with the new non-mechanical ones. More reliable.