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Discussion Starter #1
Hello

Installed new alternator and batteries. Pick-up is at normal op/temp. Everything is working as normal until I turn on headlights and raise RPM then voltage spikes and will hold until I let off fuel peddle. At idol normal. Only when I accelerate does voltage sky rocket...

Thank you!
 

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How high a voltage? I’d assume bad ground reference or regulator. How do your connections look?
 

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Did this start with the new/re man alternator , OR is the probl Why you installed the parts ?

Need more info bro
 

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Discussion Starter #4
Hey Fellas appreciate the input and questions. Ill do my best to answer them and possible overall fix as I go through this. I tried to upload a video as well but I have yet to figure how to make it smaller... it will happen. I also got in touch with a member on the FB CF page. He had a video and it was identical issue I was having. He advised me to purchase a new volt-regulator as that is what fixed his issue. It will show up today and I will install it and provide a follow up.

New/Re-Man Alternator from Orileys two of them! What is installed currently is a second new/re-man. I thought the first one bad due to the high charging, swapped for another. New Firestone batteries from Costco.

Pick up off batteries test 12.74P, 12.75D
Idling at operating temp
idling 12.66
Headlights switched on idling 15.56
Headlights switched on @ 2000rpm 16.40
Headlight switched off 12.80
Pick up shut off batteries 12.89


Please let me know if there is anything else I can check and try. Much appreciated.
 

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Batteries at 12.74 is good - that’s 100% state of charge. Idling are 12.66 is low, but the 15 and 16V levels observed is too high. Unless it’s super cold, I’d be concerned seeing much above 14.7V.

Start with basics. All connections clean? Most important is the battery connections, the battery negative to body/engine, and any additional ground on the alternator itself. I suspect that especially if a reference ground on the alternator might result in an abnormal control of the voltage regulator.

On old Euro cars with Bosch alternators (egg my old Mercedes diesels) which often produces a low voltage output at speed, and even lower output at idle, an option is to put a diode, which has a natural voltage drop, between the alternator case and voltage regulator. That added voltage drop results in a higher voltage output by the regulator.

Effectively the situation that you’re describing... Those alternators put out very little at idle, do better at 1500-2000RPM, and with a difference in the voltage reference can be made to put out a bit more.

So clean your alternator mount points, any negative reference supplemental wire, and anything else convenient. See if that helps.
 

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Recommend you check these...
908936


Section 8C-5 in the FSM linked to in this forum talks about how to get diagnostic codes and how to troubleshoot the alternator. It explicitly says to not allow over 16V as damage will occur. So Id get on this quickly!
 

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No one has mentioned the battery temp sensor. It is under the driver side battery. Easy to check, easy and inexpensive to replace. AutoZone carries them. Testing is covered in the FSM.
 

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No one has mentioned the battery temp sensor. It is under the driver side battery. Easy to check, easy and inexpensive to replace. AutoZone carries them. Testing is covered in the FSM.
a temperature sensor should dial the voltage down with temperature. Even if it incorrectly measured temperature as super low, it shouldn’t ratchet the voltage over 16V. That’s abusive for the battery.
 

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My original temp sensor kept the alternator from charging at all. Whether or not it can cause excessive voltage I don't know. It is part of the system and an easy check. No reason not to look at it.
 
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