I seem to have an electrical issue in my 68 coronet. This is the 4th alternator thats stopped working in 3 yrs. We installed a new voltage regulator 2yrs ago. Any suggestions on what to look into next??

replacement electronic reg version I am assuming. Might just be Murphys law. wouldn't hurt to clean ALL terminals/connections especially the bulkhead (bristle brush on the males/spare male on the females) and the ground paths (block to firewall/frame or block to battery neg) & you could check charging voltages/voltage drops. parts house remans?

Do you have any high draw accessories like cooling fans, stereo amps etc. IF so they may be overtaxing the alternators resulting in the failures

Is your battery ok ?? Maybe it is kinda bad and causing the alternator to be charging all the time ???

Were they all rebuilt? My experience is that you almost can't find a new (none rebuilt) alternator anymore from your local auto parts store. I had the same thing happen to me until I bought a brand new, non rebuilt one. No more trouble after that.

Do you know how are they failing?

Are the brushes failing? Bearings? Diode Bridge? Field or armature coils?

More then likely they are failing diodes which can be caused by reversed polarity in the system when jump starting a car, voltage spikes, heat, or vibration.

Knowing what fails helps to figure out if you have an external problem or just bad luck.

I had a situation a few years ago with an Autozone alternator. After installing and finding it didn't work, then doing the same thing with the replacement, the third time I went to the store I had them test the rebuilt alternator before I took it home. It charged up a storm, and I never had a lick of trouble with it. Check the new alternator before you leave the store.

I have gotten bad rebuilts from Autozone and NAPA. I paid more for the NAPA and it nearly burned my truck. When this alternator failed there were foot high flames shooting out of the alternator.
I am trying to say that no parts house has a corner on the defects market.

R.

Agree it seems reman alternators (on 40 year old cores!) are iffy. If connections, wires and VR are OK it could well be bad alternators. There are several options for "stock replacement" new... many Powermaster and some others. Check out Mancini Racing and Summit.

I am so sick and tired of this Chinese crap that every supply house (including dealers)is selling! The Chinese put out nothing but junk and we keep buying it and wondering why it fails. If you can, buy American made. Yea, it costs more but at least it usually works.

Yep, I believe theyve all been Remans. On the standard instrument panel, my alternator gage usually reads halfway between midline and charging when I get a fresh reman. Not sure where its supposed to read under normal conditions. I dont have a radio(currently), no AC, or anything extradinary receiving big draws.

If the system is working properly after starting the needle should indicate a reasonable charge rate ( 3/4 or so to the right) at a higher RPM ~2k + or so as the alternator is replenishing the battery. If the motor has been cranked for awhile when starting the initial charge rate may be higher.
After a couple of minutes the needle should be straight up or very close to it indicating little or no charge.
Be aware that at very low engine speed with higher draw accssories the needle may show a discharge ( left of center) until the RPM increases. It would then show a charge (Right of center) until the battery is once again replenished.

A constant charge rate is indicative of an issue somewhere in the system.

Thanks for the information, I appreciate it. And yes, i must have an issue elsewhere because its always showing its charging. Ill try to look into it more.

Have you considered that you may have electrical circuit active when you shut the engine down, which would be drawing down battery reserve. If the battery is continuously drawn down while car is parked, this then of course causes the alternator to go into full charge mode for possibly extended periods of time until battery is replenished again. This would reduce life expectancy.

A better method would be to use a meter so that you can measure any draw.

Simple test for this would be to disconnect ground cable and with a test light, connect one end to the negative battery post and the other to ground. Make certain switch is off and doors are closed.

If light illuminates, could be anything from a glove box or trunk light to a bad voltage regulator to an excessive draw from an alarm system to a radio wired to accessory side of ignition switch,,,,etc.

If a draw is detected and you do not know from where, an initial test would be to remove fuses until light goes out,,,this would be the guilty circuit. Would not catch a defective voltage regulator or devices on circuit breakers.