The Ford Barn

wrmyers35 · 08-12-2023, 07:14 PM

I have a brand new Nu-Rex 12 volt alternator, still in the original box that I've kept in the box for a couple years, as a spare.
I recently installed it on my 1931 SW Fordor and it will not self regulate, it constantly charges at 15 amps, and when I turn on my AC it pegs the ammeter way past the 20 amp mark!
No matter how long I run the engine it doesn't charge any less.
I have a new 12 V battery with new cables so that's not the problem.
I thought it may be the internal voltage regulator so I bought a new one from NAPA that fits late 80's GM vehicles. The one they sold me looked exactly like my original, but they weren't sure if was the same function.
Once I installed the new voltage regulator the alternator would not charge at all!
I reinstalled the original regulator and it acts just the same, it overcharges.
Does the Nu-Rex alternator use a special regulator? (It has red letters 12 SE printed on it)
Anyone got a solution for this issue?
Bill

rotorwrench · 08-12-2023, 08:24 PM

Is this alternator a GM 10si unit or something else? I know Nu-Rex uses them but they change the pulley and set them up for 1-wire operation. They sometimes need help on their first self excite but it sounds like it had a bum internal regulator. You may also have a loose wire in your system. Make sure your two terminal box studs are well connected. Check your ammeter for damage and test it by turning on the lights with a normal discharge indication. A person can use about any aftermarket voltage controller for these as long as they are 12-volt negative ground. Just make sure it is properly connected.

Also check your battery out. If it has problems then the alternator is going to try too hard to compensate for that.

Ordsgt · 08-12-2023, 09:20 PM

Call Nu rex and speak to him. I had a problem with one of his 6v alternators and he was very helpful. He told me what to do and if that didn't fix the problem send it to him and he would make it right. I did as he asked and the alternator has worked fine ever since.

wrmyers35 · 08-12-2023, 09:22 PM

Thanks for your comments!
It says Delco Remy on the back, so I assume it's a GM. I think it's a 12si since it's 12 volts, negative ground.
It's a new battery and new cables, but I haven't checked for loose wiring.
When I turn on the headlights without the engine running the ammeter shows discharge.
I added some wiring when I installed the AC, so I'll check all for loose connections.

wrmyers35 · 08-12-2023, 09:24 PM

Thanks, I think I'll try talking to Nu-Rex next week.

GeneBob · 08-12-2023, 10:48 PM

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Ordsgt is correct. I also had an issue with a NuRex alternator. I called them up and, I am sorry I forget his name, but did a couple tests as suggested and the alternator did not respond. He said it was odd that my alternator did not respond to the tests. I sent it to NuRex and they made it work. No BS, no problem, they stand behind their product.

It seems we Model A'ers don't expect the manufacturers to care after a period time has passed but I have found they really want to make things right to the best of their abilities when we simply ask.

rotorwrench · 08-13-2023, 01:01 AM

The 12si is the later higher output unit. Most one wire units are the 10si. A model A would have to have a lot of accessories to require a high output unit.

I'd let Nu-Rex handle it if they will make good on it. Rebuild kits are available for 6-volt positive earth units since so many have been converted. All they needed was an internal jumper to change polarity. The little solid state control unit is what makes it a 6-volt unit when applicable. The 12-volt units have been used for multiple decades now. My old Ford 850 tractor has a basic 12-volt Delco Remy 10si on it and has for many years. It still works like a champ.

wrmyers35 · 08-13-2023, 07:57 AM

Rotorwrench you are correct, mine is a 10si; it does not have the 'turbine' style fan.
I plan to call Nu-Rex next week and see what they say . . .

eagle · 08-13-2023, 08:47 AM

One easy check that the supplier is likely going to want you to check is the voltage output when it is running and connected to the battery.

08-12-2023, 07:14 PM	#1
wrmyers35 Member Join Date: Feb 2011 Location: Bedford, Texas Posts: 32	Nu-Rex 12V alternator Overcharging I have a brand new Nu-Rex 12 volt alternator, still in the original box that I've kept in the box for a couple years, as a spare. I recently installed it on my 1931 SW Fordor and it will not self regulate, it constantly charges at 15 amps, and when I turn on my AC it pegs the ammeter way past the 20 amp mark! No matter how long I run the engine it doesn't charge any less. I have a new 12 V battery with new cables so that's not the problem. I thought it may be the internal voltage regulator so I bought a new one from NAPA that fits late 80's GM vehicles. The one they sold me looked exactly like my original, but they weren't sure if was the same function. Once I installed the new voltage regulator the alternator would not charge at all! I reinstalled the original regulator and it acts just the same, it overcharges. Does the Nu-Rex alternator use a special regulator? (It has red letters 12 SE printed on it) Anyone got a solution for this issue? Bill Last edited by wrmyers35; 08-12-2023 at 07:16 PM. Reason: Correct typing errors

08-12-2023, 08:24 PM	#2
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Nu-Rex 12V alternator Overcharging Is this alternator a GM 10si unit or something else? I know Nu-Rex uses them but they change the pulley and set them up for 1-wire operation. They sometimes need help on their first self excite but it sounds like it had a bum internal regulator. You may also have a loose wire in your system. Make sure your two terminal box studs are well connected. Check your ammeter for damage and test it by turning on the lights with a normal discharge indication. A person can use about any aftermarket voltage controller for these as long as they are 12-volt negative ground. Just make sure it is properly connected. Also check your battery out. If it has problems then the alternator is going to try too hard to compensate for that. Last edited by rotorwrench; 08-12-2023 at 08:46 PM.

08-12-2023, 09:20 PM	#3
Ordsgt Senior Member Join Date: Sep 2020 Location: Yorktown Virginia Posts: 180	Re: Nu-Rex 12V alternator Overcharging Call Nu rex and speak to him. I had a problem with one of his 6v alternators and he was very helpful. He told me what to do and if that didn't fix the problem send it to him and he would make it right. I did as he asked and the alternator has worked fine ever since.

08-12-2023, 09:22 PM	#4
wrmyers35 Member Join Date: Feb 2011 Location: Bedford, Texas Posts: 32	Re: Nu-Rex 12V alternator Overcharging Thanks for your comments! It says Delco Remy on the back, so I assume it's a GM. I think it's a 12si since it's 12 volts, negative ground. It's a new battery and new cables, but I haven't checked for loose wiring. When I turn on the headlights without the engine running the ammeter shows discharge. I added some wiring when I installed the AC, so I'll check all for loose connections.

08-12-2023, 09:24 PM	#5
wrmyers35 Member Join Date: Feb 2011 Location: Bedford, Texas Posts: 32	Re: Nu-Rex 12V alternator Overcharging Thanks, I think I'll try talking to Nu-Rex next week.

08-12-2023, 10:48 PM	#6
GeneBob Senior Member Join Date: May 2017 Location: Denver Area Posts: 433	Re: Nu-Rex 12V alternator Overcharging Sponsored Links (Register now to hide all advertisements) Ordsgt is correct. I also had an issue with a NuRex alternator. I called them up and, I am sorry I forget his name, but did a couple tests as suggested and the alternator did not respond. He said it was odd that my alternator did not respond to the tests. I sent it to NuRex and they made it work. No BS, no problem, they stand behind their product. It seems we Model A'ers don't expect the manufacturers to care after a period time has passed but I have found they really want to make things right to the best of their abilities when we simply ask.

08-13-2023, 01:01 AM	#7
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Nu-Rex 12V alternator Overcharging The 12si is the later higher output unit. Most one wire units are the 10si. A model A would have to have a lot of accessories to require a high output unit. I'd let Nu-Rex handle it if they will make good on it. Rebuild kits are available for 6-volt positive earth units since so many have been converted. All they needed was an internal jumper to change polarity. The little solid state control unit is what makes it a 6-volt unit when applicable. The 12-volt units have been used for multiple decades now. My old Ford 850 tractor has a basic 12-volt Delco Remy 10si on it and has for many years. It still works like a champ. Last edited by rotorwrench; 08-13-2023 at 01:14 AM.

08-13-2023, 07:57 AM	#8
wrmyers35 Member Join Date: Feb 2011 Location: Bedford, Texas Posts: 32	Re: Nu-Rex 12V alternator Overcharging Rotorwrench you are correct, mine is a 10si; it does not have the 'turbine' style fan. I plan to call Nu-Rex next week and see what they say . . .

08-13-2023, 08:47 AM	#9
eagle Senior Member Join Date: Aug 2011 Location: Eagle Bend, MN Posts: 2,025	Re: Nu-Rex 12V alternator Overcharging One easy check that the supplier is likely going to want you to check is the voltage output when it is running and connected to the battery. __________________ "There are some that can destroy an anvil with a teaspoon and shouldn't be allowed to touch anything resembling a tool."