Idle voltage for 1995 Newell - Printable Version
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Idle voltage for 1995 Newell - Mad Mark - 04-21-2026
Hi Everyone! I am the new owner of coach #390.
I am having an alternator voltage fluctuation. On VMSpc I am showing between 12.8v and 13.1v at idle. When I am driving with the generator running, I am showing 14.1v to 14.6v. Generator off it 13.8-14.1.
I noticed the grounding wire seems a bit frayed where it connects to the alternator. I am going remove the air intake piping and test alternator voltage.
Any other suggestions? I apologize if this isn't the right category.
Thanks,
Mark
RE: Idle voltage for 1995 Newell - Mad Mark - 04-21-2026
I just tested the alternator and we're getting 12.8 - 12.9 at idle from the bolts on the back of the alternator. I guess I need an alternator.
Anyone else disagree?
RE: Idle voltage for 1995 Newell - Richard - 04-21-2026
Ok !
It depends on whether Keith installed a larger pulley on the alternator.
Here is the rest of the story. As it was built from the factory, the belt would slip if there was a heavy load on the alternator because there wasn’t enough wrap on the pulley. Gordon Jones devised a solution to install a larger diameter pulley but the drawback was that it slowed down the alternator at idle speed so that it didn’t quite make the target voltage.
If you have the larger pulley, you will want to keep it, and put up with the low voltage at idle.
If the genset is running, the inverters are charging the house batteries AND the engine batteries UNLESS someone has changed the circuit. Best I remember on that coach, the ignition ON closes the 300 amp Cole Hersee merge solenoid which connects the two banks. Not all Newells are wired that way.
First time, I was running the genset on that coach and noticed the ammeter showing a discharge, I wigged out. See if you are running the genset, the ammeter will show a discharge UNTIL the house batteries are charged and then it will return to normal.
The merge being activated by the ignition switch was an unusual setup on that coach. If it is still that way, be aware that starting a drive day with depleted house batteries will put a big strain on the alternator.
RE: Idle voltage for 1995 Newell - Mad Mark - 04-21-2026
(04-21-2026, 12:58 PM)Richard Wrote: Ok !I am completely okay with the low voltage at idle. It pops right up once you're driving. I was concerned that she was broken.
It depends on whether Keith installed a larger pulley on the alternator.
Here is the rest of the story. As it was built from the factory, the belt would slip if there was a heavy load on the alternator because there wasn’t enough wrap on the pulley. Gordon Jones devised a solution to install a larger diameter pulley but the drawback was that it slowed down the alternator at idle speed so that it didn’t quite make the target voltage.
If you have the larger pulley, you will want to keep it, and put up with the low voltage at idle.
If the genset is running, the inverters are charging the house batteries AND the engine batteries UNLESS someone has changed the circuit. Best I remember on that coach, the ignition ON closes the 300 amp Cole Hersee merge solenoid which connects the two banks. Not all Newells are wired that way.
First time, I was running the genset on that coach and noticed the ammeter showing a discharge, I wigged out. See if you are running the genset, the ammeter will show a discharge UNTIL the house batteries are charged and then it will return to normal.
The merge being activated by the ignition switch was an unusual setup on that coach. If it is still that way, be aware that starting a drive day with depleted house batteries will put a big strain on the alternator.
I saw the ammeter discharging too and that's why I thought something was wrong.
Awesome. Good to know everything is okay and I can put it back together. I think I will change the alternator ground at some point in the near future but it's not an emergency.
Thank you!
Mark
RE: Idle voltage for 1995 Newell - Mad Mark - 04-21-2026
(04-21-2026, 12:58 PM)Richard Wrote: Ok !
It depends on whether Keith installed a larger pulley on the alternator.
Here is the rest of the story. As it was built from the factory, the belt would slip if there was a heavy load on the alternator because there wasn’t enough wrap on the pulley. Gordon Jones devised a solution to install a larger diameter pulley but the drawback was that it slowed down the alternator at idle speed so that it didn’t quite make the target voltage.
If you have the larger pulley, you will want to keep it, and put up with the low voltage at idle.
If the genset is running, the inverters are charging the house batteries AND the engine batteries UNLESS someone has changed the circuit. Best I remember on that coach, the ignition ON closes the 300 amp Cole Hersee merge solenoid which connects the two banks. Not all Newells are wired that way.
First time, I was running the genset on that coach and noticed the ammeter showing a discharge, I wigged out. See if you are running the genset, the ammeter will show a discharge UNTIL the house batteries are charged and then it will return to normal.
The merge being activated by the ignition switch was an unusual setup on that coach. If it is still that way, be aware that starting a drive day with depleted house batteries will put a big strain on the alternator.
I also noticed that the alternator is externally regulated. Are they generally reliable units? They appear to be a hard to get part.
RE: Idle voltage for 1995 Newell - Keith Jordan - 04-22-2026
I did install the larger pulley. That alternator is not available anymore. Coach is still wired the way Richard described it. You have a spare rebuilt alternator in the basement. I don't remember if it has the larger pulley
RE: Idle voltage for 1995 Newell - Richard - 04-22-2026
Nothing magic about the regulator. You will find that Newell used some wiring on the regulator that I NEVER understood.
Oh yeah, welcome to the forum and the benefits bestowed upon you. The cost? Post when you fix things to help others in the future.
Oh yeah, if you are futzing with the alternator take care the alternator case doesn’t contact the dash air con compressor or tubing. Or else you will soon lose the r 134