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2 blown Marelli generators, 2 expensive alternators, 2 electrical mechanics and I am still having a problem with the Alfa. Backstory: Marelli generator 1 suddenly dies, replace with back-up Marelli generator 2. 2 weeks later, dynamo light comes on and Marelli generator 2 is tested to be blown. Figure bad Voltage Regulator. Give up on generators and buy alternator. Install expensive alternator 1, bypass VR, all is good. 2 weeks later, Dynamo light comes on and something is drawing from the battery. Have to disconnect hookup at positive pole after driving car. Have not 1, but 2 electrically-inclined mechanics check out the car and both conclude alternator 1 is defective. Buy expensive alternator 2, replace and everything seems fine for 2 weeks. Just yesterday, Dynamo light comes on and battery is drained. I'm frustrated that my car is broke and I can't drive it!

Internet research tells me this may be caused by 1 of 3 conditions: 1) Bad battery, 2) bad grounds or 3) bad alternator. Based on my backstory, #1 & 3 can be eliminated. I'm going with bad grounds.

The only ground I checked was the one on the sidewall. I sanded the paint off to bare metal and reattached the ground. Where are the other grounds that I need to check?
 

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By sidewall you mean the main ground strap from the engine/trans to the chassis tunnel area? The other main ground would be the battery negative (assuming negative ground) to the trunk floor. Many individual components will ground through their mountings, but I can't imagine most of them are giving you this problem.

Polarity wasn't changed, is correct for the car? I know you can alter it, I did so on my 58 Normale, but it has a Lucas generator and regulator.

Andrew
 

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Discussion Starter #3
By sidewall you mean the main ground strap from the engine/trans to the chassis tunnel area? The other main ground would be the battery negative (assuming negative ground) to the trunk floor. Many individual components will ground through their mountings, but I can't imagine most of them are giving you this problem.

Polarity wasn't changed, is correct for the car? I know you can alter it, I did so on my 58 Normale, but it has a Lucas generator and regulator.

Andrew
There's a ground that connects to the sidewall beneath the Voltage Regulator. In another thread it was mentioned to check the ground strap and the ground in the rear, by the gas tank. Don't know where to specifically look for these?

As far as I know, the polarity is the same on the alternator as it is for the car. At least, that's what I was told. Here's the alternator.

I think you know my next question: how do I check polarity?
 

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Well, if the battery had positive to the alternator/generator/regulator, and negative to ground, it was negative ground. A 58 Normale likely would have come positive ground, Lucas components. If you're talking Marelli, that must be the Veloce, and I believe they were always negative ground. Can an alternator be positive ground? I don't know.

My two Spiders don't have a ground from the gas tank to the body, but the battery ground strap in the trunk bolts to the floor right near the gas tank mount. You have to have a good ground from the battery to the body, and from the engine/trans to the body, otherwise nothing works.

Andrew
 

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There's a ground that connects to the sidewall beneath the Voltage Regulator.
"Sidewall" typically means the side of a tire. So your use of that term was confusing us. I assume that the Alfaholics alternator is internally-regulated, so you no longer have a regulator in the circuit, and as such, the ground between the regulator and fenderwell is now irrelevant. Please confirm whether there is still a regulator somewhere in the mix.

I think you know my next question: how do I check polarity?
I think Andrew meant: How was your battery originally connected? Negative ground or positive ground? Some early Alfas had positive grounds. Is it possible that the Alfaholics alternator only works with the more common negative ground, but your battery is still connected as a positive ground?

Internet research tells me this may be caused by 1 of 3 conditions: 1) Bad battery, 2) bad grounds or 3) bad alternator.
I don't agree with that; I believe there is an unlimited list of things that could be causing your generators & alternators to die. The three causes you list may be the "top three", but certainly are not exhaustive. Heck, the first Marelli generator probably died from old age.
 

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Discussion Starter #6
Yeah, I'm still learning the correct terminology. Sorry for the confusion. So, there is a ground from the alternator to the fenderwall. In the pic you can just see the ground to the bottom-right of the VR. Everything else is connected to the left of the VR, thus by-passing it. The VR remains just for aesthetics.

As far as positive ground vs. negative ground, I'm totally lost. How do I find this out?
 

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Look at the battery. Does the negative terminal's cable bolt to the body, or the positive terminal?

Andrew
 

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I'm at my office. I'll check on this once I get home and report back.
 

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In the pic you can just see the ground to the bottom-right of the VR. Everything else is connected to the left of the VR, thus by-passing it. The VR remains just for aesthetics.
I understand what you have written, and can see that some of the voltage regulator's terminals are now unconnected. When people convert to an alternator they will often leave the voltage regulator in place "just for aesthetics". I get that.

My worry is that with +12 (or maybe it's ground) connected to the lower left of the regulator, and ground (or maybe it's +12) to the top right, the regulator is somehow shorting between the two. Even though its control terminals are unconnected, perhaps the regulator is trying to do something. This is just a theory, I don't pretend to understand how 1958 Marelli regulators work - but since we're stumped for what's causing your electrical issues, you might add this one to the list.

An interesting experiment would be to rig up an isolated connection between the alternator output and the car's wiring harness (the wires now attached to the lower left terminal of the regulator as seen in the photo below) that isn't connected to the regulator. As a temporary experiment, this could just be a machine screw + nut holding the ring lugs together, wrapped with electrical tape.
 

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Discussion Starter #10
I just arrived home and the negative terminal bolts to the body.
 

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I just arrived home and the negative terminal bolts to the body.
OK, that's a good thing. 99.9% of the cars on the road today have negative ground. No doubt the alternators Alfaholics supply assume negative ground.

Scratch that possibility off the list!
 

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Discussion Starter #12
Jay,

Let me run your experiment and disconnect that bolus of wires from the VR.
 

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Discussion Starter #13
Jay,

I performed your experiment as documented in the picture. The Dynamo light still came on.
 

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My recollection is Veloces were always negative ground. Only Lucas-fitted Normales were positive ground, since that's what those components were at the time.

Andrew
 

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I performed your experiment as documented in the picture. The Dynamo light still came on.
You did connect the wires as I was imagining. But sorry, perhaps I didn't explain the purpose of experiment clearly. If having the regulator in the circuit somehow fried your existing alternator, then connecting the wires as I suggested isn't going to "heal" it.

The purpose of my experiment is to see whether connecting the power wiring separately from the regulator will allow the replacement alternator to survive. I have to believe that those alternators are generally reliable; the odds are good that something external to the alternator caused the first one to die prematurely. So installing a replacement without changing anything seems like an invitation to spend yet another £450.00

As a side note, do you need to spend another £450.00? Is it possible that a local automotive electrical shop could repair the Alfaholics alternator? Perhaps just the diodes are bad. Knowing what failed in the alternator might help diagnose what caused the failure.
 

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Discussion Starter #17
You did connect the wires as I was imagining. But sorry, perhaps I didn't explain the purpose of experiment clearly. If having the regulator in the circuit somehow fried your existing alternator, then connecting the wires as I suggested isn't going to "heal" it.
Sorry, I thought it was to eliminate the possibility of interference from the Voltage Regulator.


The purpose of my experiment is to see whether connecting the power wiring separately from the regulator will allow the replacement alternator to survive. I have to believe that those alternators are generally reliable; the odds are good that something external to the alternator caused the first one to die prematurely. So installing a replacement without changing anything seems like an invitation to spend yet another £450.00
I agree with you that the problem is external to the alternator. But what can it be???


As a side note, do you need to spend another £450.00? Is it possible that a local automotive electrical shop could repair the Alfaholics alternator? Perhaps just the diodes are bad. Knowing what failed in the alternator might help diagnose what caused the failure.
The idea of the backup alternator was to be able to drive the car without down time. Plus, the pulley on the first alternator rubbed against the body and created a loud "clang" when accelerating. I had to add a washer between the pulley and the body in order for that clanging noise to cease. I will have the first alternator looked at.
 

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Discussion Starter #19 (Edited)
That's very interesting! I wish I had my Marelli generators to check the numbers and see what kind I had, but they're at the repair shop. My car is far from original stock and is more of a hodgepodge of OEM and NOS parts pieced together to make a daily driver. Although, I lack confidence in my daily driver right now with the Dynamo light on.

Here's a question to ponder, do you think the alternator is putting out enough voltage to disengage the Dynamo light from shining? There is current going to the battery when revving the engine. Yesterday, I wanted to take the car out to a showing at some Church around the corner from me, but the Dynamo light was on and the battery tested 58% charged. I had the battery tendered all night and when I left for work at 5 AM it was completely charged. I hooked up the battery and tested it again when I came home after 2 pm and it was at 95%. Right where it should be. You would think if there was a draw on the battery that after 9+ hours it would be at less than 95% charged? Maybe the Dynamo light isn't wired correctly? I'm stumped!
 

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.. phil.. he's hookin' up a ALTERNATOR not in the parts book. Nice effort tho.

Maybe we need to start from scratch.. The battery has two terminals + and -. One is attached to the body of the car. If it is +, the car is positive ground. If - it is negative ground. Once those cables are connected that way, no matter what you do to the other components, the ground of each will be as per the battery. the only thing that needs to be done is to reverese the wires on the electric fuel pump and to flash the field on the generator to polarize it for + or -. Alternators I don't know.
 
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