68 L79 Alternator and Voltage Regulator

[Dave F.]

Re: 68 L79 Alternator and Voltage Regulator

Rich,

I don't believe the sum of the two exceeded $100, and certainly not much if it did. If you do call Sweeney Chevrolet Parts (513-782-2826), ask for Walt. He's been there forever

[Dave F.]

Re: 68 L79 Alternator and Voltage Regulator

Rich,

I don't believe the sum of the two exceeded $100, and certainly not much if it did. If you do call Sweeney Chevrolet Parts (513-782-2826), ask for Walt. He's been there forever

[Roger Legge]

Re: 68 L79 Alternator and Voltage Regulator

I have had the exact symptoms with my '68 L79 and it was the regulator. Right now it has the 'cheap' regulator from NAPA, which is the electronic model. Didn't cost much and it works. I've gone through a couple regulators over the last five or so years and that included a new mechanical regulator from GM - don't have p/n handy. The car has a generic, rebuilt alternator in it and I think it may be erratic at times based on seeing the ammeter bounce around at times. Not sure if this may, over time, cause a regulator to fail. I guess it could be a ground issue. Anyway, my first choice would be to replace the regulator with one of the electronic ones. I think I paid $13 at NAPA for mine.

Roger
#36316

[Roger Legge]

Re: 68 L79 Alternator and Voltage Regulator

I have had the exact symptoms with my '68 L79 and it was the regulator. Right now it has the 'cheap' regulator from NAPA, which is the electronic model. Didn't cost much and it works. I've gone through a couple regulators over the last five or so years and that included a new mechanical regulator from GM - don't have p/n handy. The car has a generic, rebuilt alternator in it and I think it may be erratic at times based on seeing the ammeter bounce around at times. Not sure if this may, over time, cause a regulator to fail. I guess it could be a ground issue. Anyway, my first choice would be to replace the regulator with one of the electronic ones. I think I paid $13 at NAPA for mine.

Roger
#36316

[Richard D.]

Re: 68 L79 Alternator and Voltage Regulator

Thanks Roger, that's exactly what I'm going to do for the time being, put in cheap Autostore parts just so I can keep driving the car this summer, and begin the hunt (and save up some $'s) to get the correct parts gathered together for the push on getting everything (or as much as I can) done correctly.

After all, these are not difficult to change out to correct parts when I finally do get them, and can always serve as inexpensive "spares" when I do replace them with the correct parts.

Joe Lucia, by the way, posted the p/n for the GM avaiable alt. and VR above.

Regards,

Rich

[Richard D.]

Re: 68 L79 Alternator and Voltage Regulator

Thanks Roger, that's exactly what I'm going to do for the time being, put in cheap Autostore parts just so I can keep driving the car this summer, and begin the hunt (and save up some $'s) to get the correct parts gathered together for the push on getting everything (or as much as I can) done correctly.

After all, these are not difficult to change out to correct parts when I finally do get them, and can always serve as inexpensive "spares" when I do replace them with the correct parts.

Joe Lucia, by the way, posted the p/n for the GM avaiable alt. and VR above.

Regards,

Rich

[Craig S.]

Re: 68 L79 Alternator and Voltage Regulator

Hey Jim, since you said it is a 42A, maybe you have a 696...you can sell that front cover for $$$$ money on eBay.... Craig

[Craig S.]

Re: 68 L79 Alternator and Voltage Regulator

Hey Jim, since you said it is a 42A, maybe you have a 696...you can sell that front cover for $$$$ money on eBay.... Craig

[Mike Cobine]

Re: 68 L79 Alternator and Voltage Regulator

An interesting item I ran across that might give you ideas. Back in the '70s, I saw several laternators that were going to very little charge and finally no charge. On some, I found the voltage regulator out (internal VR). Others I found one of the diode packs out, so that one phase of the voltage was gone.

After doing so tracking, it seemed all had one thing in common - jump starting another car a few months earlier. I stuck a scope on a car, jumped another, and saw several high voltage spikes run across the line. The solid state VR didn't seem to have good protection against this.

So as a result, when jumping a car, I always connect, start the good one, run 5 minutes to charge the dead one, shut off, then start the dead one. No spike into the running alternator.

However, this shouldn't apply to yours. I never found one with the mechanical regulator to blow from jumping.

But since you seem to have the same symptoms, it could be you have a bad diode pack in the alternator, if you have already been through the VR.
You can check with a scope, but not a volt meter. Voltage will be normal, but current won't because you may have only two phases running, producing much lower current. Or if one phase diode shorts, you would have the one phase charging and discharging, so you actually lose charge while it runs.

As someone mentioned, a good auto electric shop will tell you in a couple of minutes. Don't bother with the AutoZone, Pep Boys, etc. as their "tester" is
basically a voltmeter and will show good even when it isn't.

[Mike Cobine]

Re: 68 L79 Alternator and Voltage Regulator

An interesting item I ran across that might give you ideas. Back in the '70s, I saw several laternators that were going to very little charge and finally no charge. On some, I found the voltage regulator out (internal VR). Others I found one of the diode packs out, so that one phase of the voltage was gone.

After doing so tracking, it seemed all had one thing in common - jump starting another car a few months earlier. I stuck a scope on a car, jumped another, and saw several high voltage spikes run across the line. The solid state VR didn't seem to have good protection against this.

So as a result, when jumping a car, I always connect, start the good one, run 5 minutes to charge the dead one, shut off, then start the dead one. No spike into the running alternator.

However, this shouldn't apply to yours. I never found one with the mechanical regulator to blow from jumping.

But since you seem to have the same symptoms, it could be you have a bad diode pack in the alternator, if you have already been through the VR.
You can check with a scope, but not a volt meter. Voltage will be normal, but current won't because you may have only two phases running, producing much lower current. Or if one phase diode shorts, you would have the one phase charging and discharging, so you actually lose charge while it runs.

As someone mentioned, a good auto electric shop will tell you in a couple of minutes. Don't bother with the AutoZone, Pep Boys, etc. as their "tester" is
basically a voltmeter and will show good even when it isn't.

[Richard D.]

Re: 68 L79 Alternator and Voltage Regulator

Thanks Mike.

I've never "jumped started" my car yet, but I'll heed your advice!

Appreciate your info.,

Rich

[Richard D.]

Re: 68 L79 Alternator and Voltage Regulator

Thanks Mike.

I've never "jumped started" my car yet, but I'll heed your advice!

Appreciate your info.,

Rich

[Jack H.]

VERY well explained!!!! *NM*

[Jack H.]

VERY well explained!!!! *NM*