1970 Alternator Rebuild

[Tony H.]

The ammeter on my 1970 Corvette has just shown some erratic needle movement on the positive side and today has been deflecting in the negative side. My non-A/C, big block Corvette has about 95,000 miles on the original alternator (which may be on its way out). Is there a rebuild kit that is available for my alternator? Any tips on rebuild?

Thanks, Tony

[Paul E. Young]

Re: 1970 Alternator Rebuild

Tony, Most auto parts stores have a kit that contains bearings and brushes. If you need diodes you may have to go to another source. I understand that the diodes are date coded. I have seen sources in Hemmings etc. The rebuild is fairly straight forward. I have seen aluminum navel jelly used on the case with some success. Other sources do a so called reskin with a tumbler system. Good luck. Paul

[Paul E. Young]

Re: 1970 Alternator Rebuild

Tony, Most auto parts stores have a kit that contains bearings and brushes. If you need diodes you may have to go to another source. I understand that the diodes are date coded. I have seen sources in Hemmings etc. The rebuild is fairly straight forward. I have seen aluminum navel jelly used on the case with some success. Other sources do a so called reskin with a tumbler system. Good luck. Paul

[Reba Whittington]

Re: 1970 Alternator Rebuild

If you do not want to tackle this yourself, call John Pirkle in Augusta, GA, at 706 860-9047. He rebuilds to NCRS specs.

[Reba Whittington]

Re: 1970 Alternator Rebuild

If you do not want to tackle this yourself, call John Pirkle in Augusta, GA, at 706 860-9047. He rebuilds to NCRS specs.

[Tony H.]

Re: 1970 Alternator Rebuild

I bought a rebuild kit for my alternator at Pep Boys for $14. It looks pretty straight forward. I also bought a back up remanufactured alternator just in case I run into problems. If all goes well, I will just return the reman. alt. If all else fails, John Pirkle will get a call.

Thanks for the help.

Tony

[Tony H.]

Re: 1970 Alternator Rebuild

I bought a rebuild kit for my alternator at Pep Boys for $14. It looks pretty straight forward. I also bought a back up remanufactured alternator just in case I run into problems. If all goes well, I will just return the reman. alt. If all else fails, John Pirkle will get a call.

Thanks for the help.

Tony

[Gary Schisler]

Re: 1970 Alternator Rebuild

We redid my neighbors 74 alternator with a $14 kit from the local auto parts store. It had new brushes, two bearings, and an new internal voltage regulator. It didn't take more that 45 minutes for the whole deal. This was an easy one, since the bearings were really noisy. If you have a diode problem, then you will probably have to send it out. If you do that, look at the work that John Pirkle does. Truly a great looking original work of art. BTW, most alternator and starter shops can bench test your alternator in minutes.

[Gary Schisler]

Re: 1970 Alternator Rebuild

We redid my neighbors 74 alternator with a $14 kit from the local auto parts store. It had new brushes, two bearings, and an new internal voltage regulator. It didn't take more that 45 minutes for the whole deal. This was an easy one, since the bearings were really noisy. If you have a diode problem, then you will probably have to send it out. If you do that, look at the work that John Pirkle does. Truly a great looking original work of art. BTW, most alternator and starter shops can bench test your alternator in minutes.

[Joe L.]

Re: 1970 Alternator Rebuild

Tony----

If you have even a little mechanical ability and the proper tools, rebuilding an alternator is easy and quick. However, there is one thing that I must caution you about if your alternator is an original unit. The rarest Corvette ALTERNATORS are the 1969 models. That's because in 1969, internal regulator alternators were used ONLY on Corvettes and 1969 alternators had unique configuration features. The second rarest Corvette alternators are the 1970 models. These alternators retained some of the unique features of the 1969 models, although by 1970, the internal regulator-types were used on other cars so the supply is greater.

You must take all precautions to avoid damaging or breaking either case half. Internal parts are replaceable, so there is no real problem with those. When removing the split ring case end bearing, USE A PRESS, NOT A HAMMER. Also, make sure that you support the case on the inner surface of the back of the case, NOT the case mating edge.

Rebuild the alternator according to the procedures outlined in your GM Chassis Overhaul Manual and you will have no trouble. Replace the split-ring end bearing, the drive end bearing, and the brush unit. You can purchase a low cost kit, but I prefer Genuine Delco parts. Test the diode bridge, regulator, stator, and rotor using a VOM meter and following the simple test procedures outlined in the overhaul manual. These parts will either test good or bad. If bad, replace. If good, reuse. Usually, the rotor and stator will test ok, and these are the most expensive parts. If you're having the ammeter gauge indications you describe, it's possible that your diode bridge or regulator are bad. These are fairly expensive, but not that bad. If you're interested in GM parts, here's what you may need:

GM #9441879----slip ring end bearing

GM #12339293---drive end bearing

GM # 1961323---slip ring end seal

GM # 1984462---brush holder with brushes

GM # 1867531---diode bridge(+)(if needed)

GM # 1985348---diode tri(-)(if needed)

GM # 1116423---voltage regulator(if needed)

Lastly, if you don't want to do this yourself, I HIGHLY recommend John Pirkle, as the other responders have also done.

[Joe L.]

Re: 1970 Alternator Rebuild

Tony----

If you have even a little mechanical ability and the proper tools, rebuilding an alternator is easy and quick. However, there is one thing that I must caution you about if your alternator is an original unit. The rarest Corvette ALTERNATORS are the 1969 models. That's because in 1969, internal regulator alternators were used ONLY on Corvettes and 1969 alternators had unique configuration features. The second rarest Corvette alternators are the 1970 models. These alternators retained some of the unique features of the 1969 models, although by 1970, the internal regulator-types were used on other cars so the supply is greater.

You must take all precautions to avoid damaging or breaking either case half. Internal parts are replaceable, so there is no real problem with those. When removing the split ring case end bearing, USE A PRESS, NOT A HAMMER. Also, make sure that you support the case on the inner surface of the back of the case, NOT the case mating edge.

Rebuild the alternator according to the procedures outlined in your GM Chassis Overhaul Manual and you will have no trouble. Replace the split-ring end bearing, the drive end bearing, and the brush unit. You can purchase a low cost kit, but I prefer Genuine Delco parts. Test the diode bridge, regulator, stator, and rotor using a VOM meter and following the simple test procedures outlined in the overhaul manual. These parts will either test good or bad. If bad, replace. If good, reuse. Usually, the rotor and stator will test ok, and these are the most expensive parts. If you're having the ammeter gauge indications you describe, it's possible that your diode bridge or regulator are bad. These are fairly expensive, but not that bad. If you're interested in GM parts, here's what you may need:

GM #9441879----slip ring end bearing

GM #12339293---drive end bearing

GM # 1961323---slip ring end seal

GM # 1984462---brush holder with brushes

GM # 1867531---diode bridge(+)(if needed)

GM # 1985348---diode tri(-)(if needed)

GM # 1116423---voltage regulator(if needed)

Lastly, if you don't want to do this yourself, I HIGHLY recommend John Pirkle, as the other responders have also done.

[Tony H.]

Re: 1970 Alternator Rebuild-Completed

Thanks for the help on this one. I did the quick repair by carefully dismantling the unit, cleaning it, replacing brushes, springs and diode trio followed by re-assembling. I also tested the other major parts with a VOM and found no problems. The ammeter showed a steady positive reading after I completed the installation. Now I am ready for Pittsburgh. BTW, from comparison of the replacement parts, the brushes were very worn (40-50% gone) and the springs had lost much of their compression.

Thanks again for all the help.

Tony

[Tony H.]

Re: 1970 Alternator Rebuild-Completed

Thanks for the help on this one. I did the quick repair by carefully dismantling the unit, cleaning it, replacing brushes, springs and diode trio followed by re-assembling. I also tested the other major parts with a VOM and found no problems. The ammeter showed a steady positive reading after I completed the installation. Now I am ready for Pittsburgh. BTW, from comparison of the replacement parts, the brushes were very worn (40-50% gone) and the springs had lost much of their compression.

Thanks again for all the help.

Tony

[Jack H.]

One last check

Being at the Zion Regional, I didn't have the opportunity to post my two cents before you jumped into the rebuild. Here goes.

(1) First question is to ask if the rebuild's really necessary. (2) Erratic ammeter deflection (jumping +/-) instead of consistently

reading low charge and/or discharge, is frequently a problem

external to the alternator. See archieves and check the integrity

of the alternator side terminal connector as well as connections

to horn relay B+ engine compartment bus. Flakey/intermittent

connection(s) here are common.... (3) Taking alt off the car (test at parts store on 'ding ding' box)

and/or doing overhaul can 'appear' to solve the problem but it

comes back to haunt you because you haven't fixed the intermittent

contact -- symptoms simply went away temporarily because you did

disconnect/reconnect.... (4) Taking alt to parts store for check out on 'ding ding' box is NOT

proof positive of unit integrity -- doesn't exercise alt through

it's full RPM range, doesn't let it heat soak to stress diode

junction puncture conditions that can 'heal' then 're-appear' based

on thermal stress. (5) If alt's seen 95K miles, rebuild is a good idea anyway because

you're nearing the life limits of front/rear bearings. (6) There's a big difference in quality/longevity of made in Taiwan

bearing sets vs. made to GM spec components -- price/cost too! (7) Same goes for internals like brush/regulator modules. (8) If original DR diode/bridge checks good, there's no need to

replace. This is reinforced by the ABSENSE of most rebuild kits

containing diode bridge components! (9) Good luck!

[Jack H.]

One last check

Being at the Zion Regional, I didn't have the opportunity to post my two cents before you jumped into the rebuild. Here goes.

(1) First question is to ask if the rebuild's really necessary. (2) Erratic ammeter deflection (jumping +/-) instead of consistently

reading low charge and/or discharge, is frequently a problem

external to the alternator. See archieves and check the integrity

of the alternator side terminal connector as well as connections

to horn relay B+ engine compartment bus. Flakey/intermittent

connection(s) here are common.... (3) Taking alt off the car (test at parts store on 'ding ding' box)

and/or doing overhaul can 'appear' to solve the problem but it

comes back to haunt you because you haven't fixed the intermittent

contact -- symptoms simply went away temporarily because you did

disconnect/reconnect.... (4) Taking alt to parts store for check out on 'ding ding' box is NOT

proof positive of unit integrity -- doesn't exercise alt through

it's full RPM range, doesn't let it heat soak to stress diode

junction puncture conditions that can 'heal' then 're-appear' based

on thermal stress. (5) If alt's seen 95K miles, rebuild is a good idea anyway because

you're nearing the life limits of front/rear bearings. (6) There's a big difference in quality/longevity of made in Taiwan

bearing sets vs. made to GM spec components -- price/cost too! (7) Same goes for internals like brush/regulator modules. (8) If original DR diode/bridge checks good, there's no need to

replace. This is reinforced by the ABSENSE of most rebuild kits

containing diode bridge components! (9) Good luck!