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> Bosch Alternator questions
TRP
post Mar 13 2026, 04:20 PM
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Hello Gang!

While the motor is out being rebuilt I figured I would look at the starter and alternator and replace what might need replacing. The starter has a cracked cap on the solenoid, so I've ordered a new starter, will be here Monday. I'll ship the core back and recoup some of that money.

The alternator (Al75x) makes a funny noise when I spin it. It appears to be older possibly the original to the motor (82k miles), so I think I'm going to replace it while it's out. I ordered one from Pelican, they called to let me know that the one they had is sold and they didn't know when they would get more. Sierra Madre is out as well. Is this something I can just get from my FLAPS? I understand that it's doubtful that they will have on on the shelf, but is there any issue with going Oriley or Autozone? A Bosch Al75x should be universal, no?

Any benefit/risk with going with the 70amp unit?

Where is the voltage regulator on a 1975? is that hiding over on the relay board?

Thanks!
Ted
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Ishley
post Mar 13 2026, 05:37 PM
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I bought a 75 amp off ebay... ~$350. Works great... I have about 6K miles on it. Moved the pulley over and no core returned. I did replace the Regulator on my '72/4 after a year as my Voltage would jump around a bit. I have replaced my fog lights with driving lights and I have a small sub woofer. I also changed to a WOSP hi-torque starter from Pelican. All and all it seems to charge well. I'm guessing these are not really 75 amp. I remember someone had a post and said it tested lower.

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fiacra
post Mar 13 2026, 05:41 PM
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QUOTE(TRP @ Mar 13 2026, 02:20 PM) *

Hello Gang!

While the motor is out being rebuilt I figured I would look at the starter and alternator and replace what might need replacing. The starter has a cracked cap on the solenoid, so I've ordered a new starter, will be here Monday. I'll ship the core back and recoup some of that money.

The alternator (Al75x) makes a funny noise when I spin it. It appears to be older possibly the original to the motor (82k miles), so I think I'm going to replace it while it's out. I ordered one from Pelican, they called to let me know that the one they had is sold and they didn't know when they would get more. Sierra Madre is out as well. Is this something I can just get from my FLAPS? I understand that it's doubtful that they will have on on the shelf, but is there any issue with going Oriley or Autozone? A Bosch Al75x should be universal, no?

Any benefit/risk with going with the 70amp unit?

Where is the voltage regulator on a 1975? is that hiding over on the relay board?

Thanks!
Ted


VR is on the relay board. If you have a good quality original alternator I would have it rebuilt. I would not get an alternator from your O'Rileys or Autozone. Just my two cents. It might be a bit of a drive for you but Alternators Unlimited on San Pablo Ave. in Berkeley is the go-to place around here for rebuilding an alternator. I would expect there is probably someone more local to you. Good luck.
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TRP
post Mar 13 2026, 06:31 PM
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I will give the shop out in Berkeley a call and ship one of these two alternators out to them, maybe both!

Thanks for the info.

Ted
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porschetub
post Mar 13 2026, 06:42 PM
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QUOTE(TRP @ Mar 14 2026, 11:20 AM) *

Hello Gang!

While the motor is out being rebuilt I figured I would look at the starter and alternator and replace what might need replacing. The starter has a cracked cap on the solenoid, so I've ordered a new starter, will be here Monday. I'll ship the core back and recoup some of that money.

The alternator (Al75x) makes a funny noise when I spin it. It appears to be older possibly the original to the motor (82k miles), so I think I'm going to replace it while it's out. I ordered one from Pelican, they called to let me know that the one they had is sold and they didn't know when they would get more. Sierra Madre is out as well. Is this something I can just get from my FLAPS? I understand that it's doubtful that they will have on on the shelf, but is there any issue with going Oriley or Autozone? A Bosch Al75x should be universal, no?

Any benefit/risk with going with the 70amp unit?

Where is the voltage regulator on a 1975? is that hiding over on the relay board?

Thanks!
Ted

I believe X in the part number denotes and exchange unit ,would suspect the original was most likely exchanged as a core for replacement ,the early exchange units were pretty good but newer on don't appear to be that great ,I have done my share of Bosch rebuilds on altenators ,the 55amp units are are a DIY job if only doing brushes and bearing ,when you need diode work in gets put done to a suitable shop .
I believe the 75 amp unit fits with a change to vanagon unit which has and external cooling fan .
Good luck.
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brant
post Mar 13 2026, 06:43 PM
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I have a couple rebuilds from the Berkeley shop if your in a hurry

Can sell one

But sending cores and waiting is good advice
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JeffBowlsby
post Mar 13 2026, 08:25 PM
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Uh oh…

Google says Alternators Unlimited in Berkeley is permanently closed as of this month.

@TRP
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TRP
post Mar 13 2026, 08:49 PM
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QUOTE(JeffBowlsby @ Mar 13 2026, 07:25 PM) *

Uh oh…

Google says Alternators Unlimited in Berkeley is permanently closed as of this month.

@TRP


Naturally...

Thank you for the heads up. There is an old alternator / generator and starter repair shop in Gilroy, under 10 miles from my house. I will swing by there next week and see what they say.

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MartyYeoman
post Mar 13 2026, 08:53 PM
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If you're looking for a reputable rebuilder, might I suggest, talking to machine shops around your local general aviation airports. They're in the no mistakes business. You'll probably get sound advice there.
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