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 Post subject: Did my ammeter die?
PostPosted: Wed Apr 28, 2021 12:01 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 12922
Location: Fircrest, WA
Car Model: 76 D100
Vehicle: 1976 D100
Electrical system is still all stock.

I had this truck for a few years and the charging system was fine, other than the typical dim dash lights due to voltage drop through the system. Lasst year I swapped out the newer chrome voltage regulator with a NOS Mopar voltage regulator. I also installed a grpound loop between the case of the alternator, the voltage regulator, and the negative battery terminal.

A few months ago I finally installed a voltmeter. To my surprise, the voltmeter showed the alternator putting out 14.5-15 volts at all times the engine was running, except for some odd instances where the engine was idling slow and the output dropped to around 11.5-12. But about 98% of the time the voltmeter showed 14.5-15 volts.

Last week I got in the truck to run some errands and I saw the ammeter showed discharge and the voltmeter was reading close to 10 volts with the engine running. The night before everything had been fine. Using a hand-held voltmeter, I double checked the voltage at the output terminal on the alternator and at the + terminal of the battery. Both showed 11.2 with the engine running.

I changed alternators and no difference. I checked all connections and they are good.

I know I have about a 2 volt drop across the ignition switch, but I am fairly certain that is not the cause of the no-charge problem.

Could this non-charging problem be related to a failed ammeter? When time allows I fully intend to bypass the full-flow ammeter on this truck, but it is still hooked up for now and it appeared to be working fine.

Next on the list of things to do is swap out the NOS voltage regulator with another one, but could my no-charge problem be caused by the ammeter? All electrical devices work fine, the battery just isn't being charged.

Any constructive input is appreciated.


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 Post subject: Re: Did my ammeter die?
PostPosted: Wed Apr 28, 2021 12:45 pm 
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Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6230
Location: So California
Car Model: 64 Plymouth Valiant
If the ammeter is showing a discharge, it's not dead; current is going thru it (although in the wrong direction).

If the ammeter wasn't passing any current thru it, it would be showing zero.

Sounds more like a voltage regulator problem.

_________________
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64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

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 Post subject: Re: Did my ammeter die?
PostPosted: Wed Apr 28, 2021 2:32 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 12922
Location: Fircrest, WA
Car Model: 76 D100
OK, thanks. That would be disappointing since it is a NOS unit,but I guess it has sat on the shelf for about 40 years. Not surprising if it failed.


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 Post subject: Re: Did my ammeter die?
PostPosted: Thu Apr 29, 2021 5:14 pm 
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Board Sponsor
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Joined: Tue Oct 29, 2002 8:27 pm
Posts: 9711
Location: Salem, OR
Car Model:
Quote:
If the ammeter is showing a discharge, it's not dead; current is going thru it (although in the wrong direction).


x2

Quote:
Sounds more like a voltage regulator problem.


If it's full tilt to the D side especially running with the headlights on then I would also suspect that...if not
more than a notch over I might be inclined to pull fuses 1 at a time to see if any change occurs. Another
issue that has happened in some of my old mopars, you might check to make sure that the main charging
lead to the alternator still is intact at the eye connector, and also that there are no burn marks/shorts
on the lead (on A-bodies it burns and shorts to the valve cover).

Good Luck!


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 Post subject: Re: Did my ammeter die?
PostPosted: Thu Apr 29, 2021 6:12 pm 
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Turbo EFI
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2067
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
I had a 79 ramcharger that I installed the 100a alternator Left over from the cordoba that I had owned before the ramcharger. Worked GREAT until one day a few months later I went to jump a dead car with my ramcharger, and that alternator went full tilt. I was standing between my truck and the dead car, I happened to look towards my truck and I could see a plume of smoke from within, thru the windshield. I thought my whole truck was going to burn down. I had gotten the dead car started, and was unhooking the cables as I saw what I did, I discovered that the ammeter had let it's smoke out and I had a blob in the dash where it had been. I wound up buying a stewart warner -100-0-+100 ammeter and putting it in the new hole that I had created in the dash.


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 Post subject: Re: Did my ammeter die?
PostPosted: Thu Apr 29, 2021 8:37 pm 
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Turbo EFI

Joined: Sat Feb 18, 2006 2:19 pm
Posts: 1376
Car Model:
The connections inside voltage regulator connector they have split apart https://www.rockauto.com/en/moreinfo.ph ... 55&jsn=431


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 Post subject: Re: Did my ammeter die?
PostPosted: Thu Apr 29, 2021 11:41 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 12922
Location: Fircrest, WA
Car Model: 76 D100
Got it. I will dig through my stash and see if I have any more VRs I pulled from parts cars over the years, and then hit up my local parts store and hope the new VR works.


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 Post subject: Re: Did my ammeter die?
PostPosted: Sun May 02, 2021 8:59 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 12922
Location: Fircrest, WA
Car Model: 76 D100
matv91 wrote:
The connections inside voltage regulator connector they have split apart https://www.rockauto.com/en/moreinfo.ph ... 55&jsn=431


Matv91 gets the prize. Connection was loose or not good. Wiggling the plug fixed it.


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 Post subject: Re: Did my ammeter die?
PostPosted: Mon May 03, 2021 1:41 pm 
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Turbo EFI
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Joined: Fri Dec 30, 2005 2:49 pm
Posts: 1053
Location: Houston, TX
Car Model:
Good to hear you found the problem.

Related question: Is it normal for the alternator to be putting out 15 volts with a healthy VR?

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
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 Post subject: Re: Did my ammeter die?
PostPosted: Mon May 03, 2021 3:04 pm 
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Turbo EFI
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2067
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
Could be, depends on battery condition and such, would be the absolute highest I would want to see. 13.5- 14.7 would be the typical expected range.


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 Post subject: Re: Did my ammeter die?
PostPosted: Mon May 03, 2021 7:24 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 12922
Location: Fircrest, WA
Car Model: 76 D100
Stupid double post deleted.


Last edited by Reed on Mon May 03, 2021 7:25 pm, edited 1 time in total.

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 Post subject: Re: Did my ammeter die?
PostPosted: Mon May 03, 2021 7:25 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 12922
Location: Fircrest, WA
Car Model: 76 D100
I think the alternator is putting out more volts than desireable, but the battery in the truck is old and flakey. I uspect a newer battery in better condition would let the charging system op[erate closer to 14.5 volts. I should replace the battery but have other things to take care of first. As long a it holds enough of a charge to start the truck and lets the engine run, I will keep running it.


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 Post subject: Re: Did my ammeter die?
PostPosted: Tue May 04, 2021 7:26 pm 
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Board Sponsor & Moderator
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Joined: Thu Oct 17, 2002 7:27 pm
Posts: 12861
Location: Park Forest, Illinoisy
Car Model: 68 Valiant
15 isn't overly frightening, but much higher and bad things await.

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 Post subject: Re: Did my ammeter die?
PostPosted: Wed May 05, 2021 4:45 am 
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EFI Slant 6

Joined: Sat Aug 23, 2003 8:05 pm
Posts: 271
Car Model:
I chased a high voltage issue for weeks. Turned out the newer Voltage Regulator from Rockauto, Standard Motor Products (VR125???), was faulty from the get-go. Ordered a stock looking one from ebay and all is well. 13.5-14.5 volts all day long.


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 Post subject: Re: Did my ammeter die?
PostPosted: Wed May 05, 2021 12:59 pm 
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Supercharged
User avatar

Joined: Sun Nov 03, 2002 9:20 pm
Posts: 12922
Location: Fircrest, WA
Car Model: 76 D100
The charging system on this truck has put out 15 volts both with a new no-name chrome VR and a 40+ year old NOS Mopar unit. I believe the problem lies somewhere other than the VR.


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