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Discussion Starter · #1 · (Edited)
My regulator recently failed and apparently the dozen plus used regulators I have aren't any better.
I decided to go with a newer style regulator that bolts onto the back of the alternator. I temporarily installed a jumper wire from my old harness. The amp light comes on as it should but doesn't go off when it should nor is there any indication that it is charging.

Any ideas?

Harold
 

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Discussion Starter · #2 ·
My regulator recently failed and apparently the dozen plus used regulators I have aren't any better.
I decided to go with a newer style regulator that bolts onto the back of the alternator. I temporarily installed a jumper wire from my old harness. The amp light comes on as it should but doesn't go off when it should nor is there any indication that it is charging.

Any ideas? View attachment 437719

Harold
 

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Defective Bulb..... 😉
 

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Discussion Starter · #4 ·
Something is defective.
I haven't checked any of the fusible links because it's been charging, just very erratically. Quick test with the old regulator showed as much as 14v but the gauge was constantly twitching and was only stable at idle or when the lights were on. No charge or discharge.

Harold
 

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If it’s twitching, maybe a grounding problem?
 

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Discussion Starter · #6 ·
It's been a reliable daily driver for quite some time now. I finally resolved the starting issue and this seemed to come out of nowhere.

Harold

P.S. I did hook the ground up but will double check it.
 

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My regulator recently failed and apparently the dozen plus used regulators I have aren't any better.
I decided to go with a newer style regulator that bolts onto the back of the alternator. I temporarily installed a jumper wire from my old harness. The amp light comes on as it should but doesn't go off when it should nor is there any indication that it is charging.

Any ideas?

Harold
I have a 45 Amp (1974 Manta/Ascona, actually tested at 51 amps) alternator on my GT. I also have the 55 amp version ('75 Manta/Ascona, tested at 71 amps) as a standby. I went with a modern electronic regulator. There are several types on eBay, just search for "Bosch electronic regulator" such as these (I use the one with the adjustable voltage pot, but I have the other one as a spare):

ALTERNATOR HD ADJUSTABLE EXTERNAL VOLTAGE REGULATOR Fits BMW 1600 1800 2000 2002 | eBay

External Regulator for Bosch Alternators; 12-Volt; 14.3 Set Point B-Circuit | eBay .

Works perfectly, and simply replaces the original electro-magnetic regulator, which by definition is a piece of crap.

How is that wired, Harold? Does the amp meter show it charging? If the blue wire from the amp light isn't connected to the alternator "field", then it will always have a difference in voltage, and the amp light will stay lit.
 

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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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Keith, Am I assuming correctly that both of the above can be used on a standard original alternator. Also the first one says HD Adjustable - can you explain what that means and how that works. Also do you recommend one over the other. Thanks, Carl
 

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Keith, Am I assuming correctly that both of the above can be used on a standard original alternator. Also the first one says HD Adjustable - can you explain what that means and how that works. Also do you recommend one over the other. Thanks, Carl
Yes, the new electronic Bosch-style regulators simply replace the OEM regulator on externally regulated Bosch alternators. Plug and play.

The adjustable model has a "pot" , aka potentiometer. Came set at 13.5 volts, but I played with the pot, and I could set the voltage between 12 and 15 volts. I set it back to 13.5 volts as that is the happy place for conventional batteries.

I like to have things "adjustable" , so I use the pot version. But I ran the pre-set version for a few days, and it worked perfectly, and ran at a shade under 14 volts, which is also fine.
 
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Discussion Starter · #11 ·
Update, I added a picture to my first post of an OE 45 amp brush holder beside the newer bolt on internal regulator. Years ago a Georgia guy, "Halo effect", shared with me the internal voltage regulator swap. I'm just now getting around to it. O'Reilly's Auto doesn't have the harness adapter to test the three terminal alternator but they do have a plug for an early '80's BMW alternator with the internal regulator. ;) I was able to test a couple of alternators and picked the one that produced more voltage than the battery. It failed the "ripple" test but passed everything else. Looks like it will get me by until I can get one rebuilt.

Harold
P.S. I'll probably keep the original three terminal connector as an option just in case. I will have to work on something a little less "rigged" than the jumper wire that is currently plugged into the original harness.
 

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Why not just upgrade the alternator?
 

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Discussion Starter · #13 ·
Why not just upgrade the alternator?
Thought I did, I went from a non-working alternator to one that works and has an internal regulator. We drive our Opel GT's. I have a '98 Dodge 2500 truck and an Opel GT. It can be a hardship if I start something that I can't finish fairly quickly. Switching to a newer alternator and having to fabricate a bracket and possibly rework the adjustment bracket PLUS worrying about it overcharging and burning up my amp meter have very little appeal to me. Not many years ago when my wife was working two jobs she was putting 300+ miles a week on one of our GT's.

Harold
 

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Thought I did, I went from a non-working alternator to one that works and has an internal regulator. We drive our Opel GT's. I have a '98 Dodge 2500 truck and an Opel GT. It can be a hardship if I start something that I can't finish fairly quickly. Switching to a newer alternator and having to fabricate a bracket and possibly rework the adjustment bracket PLUS worrying about it overcharging and burning up my amp meter have very little appeal to me. Not many years ago when my wife was working two jobs she was putting 300+ miles a week on one of our GT's.

Harold
The bracket concerns are real, but not very difficult. The over charging thing is not a problem. The alternator will only supply what the car needs and nothing more. Capacity is not related to delivery just the same as having a huge amp hour battery in the car would not cause any problems unless a device in the car asked for more amps than the wires could handle.
 

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Discussion Starter · #15 ·
The over charging thing is not a problem. The alternator will only supply what the car needs and nothing more. Capacity is not related to delivery just the same as having a huge amp hour battery in the car would not cause any problems unless a device in the car asked for more amps than the wires could handle.
So you're telling me that if I somehow run my battery down, jump or push start my GT, that it won't fry my amp meter when it starts charging at ~100 amps.
I think the best argument for an "upgrade" is the ability to be able to walk in and out of almost any auto parts with a replacement in hand.

Harold
 

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Discussion Starter · #16 ·
I have two GT's with CS style alternators. One, the Old Hag, functions flawlessly and the other I haven't been able to sort out. I think I've fixed the belt shredding problem but it still won't charge and no one can tell me why it doesn't.

Harold
 

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I have two GT's with CS style alternators. One, the Old Hag, functions flawlessly and the other I haven't been able to sort out. I think I've fixed the belt shredding problem but it still won't charge and no one can tell me why it doesn't.

Harold
So you're telling me that if I somehow run my battery down, jump or push start my GT, that it won't fry my amp meter when it starts charging at ~100 amps.
I think the best argument for an "upgrade" is the ability to be able to walk in and out of almost any auto parts with a replacement in hand.

Harold
Before I took the ammeter out of my GT the 105 amp alternator never fried it. I saw some very heavy charging going on but it never was bad enough to fry anything. That said, I was concerned which is why I now have a voltmeter.
 
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So you're telling me that if I somehow run my battery down, jump or push start my GT, that it won't fry my amp meter when it starts charging at ~100 amps.
I think the best argument for an "upgrade" is the ability to be able to walk in and out of almost any auto parts with a replacement in hand.

Harold
Before I took the ammeter out of my GT the 105 amp alternator never fried it. I saw some very heavy charging going on but it never was bad enough to fry anything. That said, I was concerned which is why I now have a voltmeter.
I put a 100 amp alternator in my wagon (when it was stock). One day when the battery was completely dead, I jump started it and took it for a drive. It quickly fried the ammeter. Really smoked it!
 

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I put a 100 amp alternator in my wagon (when it was stock). One day when the battery was completely dead, I jump started it and took it for a drive. It quickly fried the ammeter. Really smoked it!
That is the problem with old style ammeters. They are actually a voltmeter attached across a low resistance, high current shunt resistor. The resistor is in series between the generator output and the battery and rest of the electrical system. If the resistor is 0.01 ohm, then 30 amps shows a 0.3V drop across the resistor, which is calibrated to read 30 A. Reversing the current flow reverses to polarity which is how + or - current flow is indicated.

These are usually fine wire resistors and they definitely have current ratings. Sometimes the shunt is internal to the ammeter sometimes external. The problems is if the resistor is damaged or becomes open the path for high current flow is broken. Worse, once the shunt resistor burns out, the meter circuit itself may follow.

There are ammeters that uses very high current solid state bypass devices. Better still, replace the ammeter with a voltmeter, connect the alternator to the battery and watch the indicated voltage reading.
 
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