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Discussion Starter #1
65 Convertible with a 5.0 transplant. When driving the amp gauge needle is dead center but is constantly jumping, about every second, 1/8 of the way to the right toward the "C".

If I turn the heater on the needle jumps twice as fast. If I turn the headlights on the needle again jumps twice as fast and it comes back to the left it passes center so that the needle is actually wagging back and forth.

I know nothing about electrical, so feel free to "dumb it down" for me and please let me know where to start to get this figured out.

Had some work done awhile back where the steering column was removed. Afterward the horn no longer worked and I think that may be when the amp needle started jumping. My bad, but I have yet to fix the horn, figured its probably just a contact but I suppose there could be a connection there with the amp gauge acting up ?

Thanks !
 

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Do you have an original mechanical regulator? If so, it might be just the regulator "kicking in and out?" Just a thought.
 

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Discussion Starter #3
I replaced the voltage regulator several years ago...forget which type I bought. I'll take a look and let ya know.
 

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my first thoughts as well. I find the modern solid state regs work the best

second thoughts is a main ground issue between battery and block and chassis

third thought is check the alt wiring, did they wire it for a idiot light or gauge

IIRC theres a different harness for each

the car or electrons wont know what motor you have in there so a 5.0 or anything else imo is out of the equation
 

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If you have the factory-installed 5-gauge cluster, you have a real (inductive) ammeter, and it can be quite sensitive, reacting to power spikes in the charging system. 66-73 "ammeters" in Mustangs were passive, and slow to react if they work at all. (Cleaning all the electrical connectors can often restore function).
 

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Thanks for the replies. The voltage regulator I installed is electronic, Motorcraft 5U2J-10316-AA. Been running it for about 5 years. The wire connection is very loose though, I had to wedge cardboard between the spade plug and the radiator support in order for it to be snugly held in place. Yeah, I know far from the right fix, feel free to call me Bubba.

I'll use a voltmeter to check how many volts are getting to the battery with it running tomorrow. Saw another post where a VR was not working properly- voltmeter read 18 volts at battery and someone said that situation will ruin it eventually.
 

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The engine is a transplant, but is the alternator a 3G? If so you can't use an amp gauge with a 3G, you will need a voltmeter. The ammeters can be converted to voltmeters.
 

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Discussion Starter #8
Sorry, what is a 3G alternator ? It's an aftermarket alternator in the car- installed it about 5 years ago when I bought the electronic VR.

I should start another thread with this question but in case someone wants to answer it- what are the pros/cons of using a 1 wire alternator and not using a voltage regulator at all ?

Thanks again-
 

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Sorry, what is a 3G alternator ? It's an aftermarket alternator in the car- installed it about 5 years ago when I bought the electronic VR.

Thanks again-

The classics had Generation 1 (1G) alternators, 2G came out in 1982 but had several recalls because of fires. The 3G is very popular because it has higher output at low rpm and came out in 1994. There are even newer generations. You will have to verify what you are using. Someone more familiar with the differences can describe them for you, or you can do a search.
 

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If it was fine and just started "out of the blue", get yourself a new "noise suppressing" capacitor that is mounted above the regulator (ground) and connected via bullet connector to the wire coming from the regulator A or A+ terminal. The capacitor is there to absorb the voltage surge of the regulator cut out circuit.
 

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The voltage regulator I installed is electronic, Motorcraft 5U2J-10316-AA.
It's an aftermarket alternator in the car- installed it about 5 years ago when I bought the electronic VR.

I don't know of any aftermarket alternator that would use a Ford voltage regulator. In fact I would bet that most aftermarket alternators are internally regulated Delco 10si alternators sold in disguise as a 1 wire alternator.
Are you sure you have an aftermarket alternator connected to a Ford voltage regulator?
 

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Discussion Starter #12
Sorry, it's a 1 G alternator in the car now- it hooks up to the original wiring harness. By calling it an aftermarket I just meant it's not the original alternator.

I checked the voltage at battery with the car running and it read 12.72 so looks like its time to upgrade to a 3G.

Thanks again for everyone's help.
 

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The wire connection is very loose though, I had to wedge cardboard between the spade plug and the radiator support in order for it to be snugly held in place. Yeah, I know far from the right fix, feel free to call me Bubba.
this part really bothers me, fix this connection asap so it is tight all of the time. cardboard is not an acceptable material to snug up an electrical connection anywhere under the hood of a car. if you need advice on how to fix that, post a pic of it.

Sorry, it's a 1 G alternator in the car now- it hooks up to the original wiring harness. By calling it an aftermarket I just meant it's not the original alternator.

I checked the voltage at battery with the car running and it read 12.72 so looks like its time to upgrade to a 3G.

Thanks again for everyone's help.
12.72 volts is actually a very good voltage to have at the battery with the engine running at idle, if you rev the engine up a 1000 or so rpm does the voltage go up to 13.5 or so? if so then i'm not seeing anything wrong that you would need to replace the alternator.
 

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Thanks for the replies. The voltage regulator I installed is electronic, Motorcraft 5U2J-10316-AA. Been running it for about 5 years. The wire connection is very loose though, I had to wedge cardboard between the spade plug and the radiator support in order for it to be snugly held in place. Yeah, I know far from the right fix, feel free to call me Bubba.
Okay, Bubba. Remove the plug from the regulator and look at the pins inside the plug. My guess is that, over the years, the female connectors have been "stretched". You can remove the connectors and wires from the plug using a heavy-duty paper clip with the end flattened between a hammer and a vise and then replace the terminal ends with some new ones and re-insert in the plug. That should help with "loose connections".

Also, if you haven't checked the noise suppressing capacitor yet don't forget about it, but also check all your connections including your ground at the engine block and ground cable between the block and firewall.
 
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