charging system issues

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spikekid999

MOPAR OR NO CAR!!!
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ok on my 74 dart I have some charging issues.
sometimes the volt gauge will peg to full charge, then after a while itll go back down to normal. a couple years ago I had it burn the battery wire stud right off the alternator on a road trip. got it replaced, but it would still peg out at full charge on my way home, so I would pull over and disconnect the voltage regulator for a while and keep going. ive read about people bypassing the factory volt gauge, will this fix my problem? any diagrams on hw to go about doing so?

also on my 5th ave I'm trying to save weight and want to do a denso alternator swap, since no one on the f/j/m site have done this, what year/model Toyotas will work? also is there a wiring diagram for the Toyota pig tail?
 
Voltmeter? You don't have one unless your replaced the ammeter.

However...........

The most probable causes of overcharging............

1....poorly grounded regulator. Scrape the firewall and regulator flange clean and use star lock washers. Better, run a no10 wire direct from battery (or engine block) to one of the regulator mounting bolts

2....bad regulator or poor connection in the regulator connector

3....problem in the brush holder of the alternator. One field terminal (blue) goes to switched 12V ignition power. The second field terminal (green) goes back to regulator which controls "the amount of ground" so to speak. IF THAT BRUSH holder is shorted to ground ....and can be part of the time..... the alternator will charge full output
 
yes ammeter, been awile since ive been able to look at the dash of my dart

ive swapped out regulaters and checked the ground to make sure it was good and it still over chargers, even with the swapped out alternator
 
Time for more serious work. There are three or four areas of concern.

First read this article:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Now, even if you don't perform this mod, for testing, temporarily bypass your ammeter by running a big wire, at least no 10, or better, a pair of no10's in parallel, direct from the alternator output stud to the battery. You'll have to monitor battery voltage with a a multimeter or temporarily rig a voltmeter in the car, as the ammeter won't be accurate

Check the hot side harness for voltage drop by hooking your voltmeter to the blue field wire on one probe, and hook the second probe to battery positive. Turn the key to "run" but with the engine off

You hope to see very low voltage, the less the better. More than about .3V (three tenths of one volt) means you have poor connections in the "hot" side of the circuit. Most likely suspects are bulhead connector, ammeter / ammeter connections, ignition switch connector, the switch, or in rare cases the "in harness splice."

Next actually check the regulator ground. To do that start engine and run at good fast idle. Stick one probe of your multimeter onto the battery NEG terminal, and the other directly onto the regulator mounting flange. Once again, you are hoping for a very low reading, lower the better, and zero would be perfect.

CLEAN your battery terminals, using a good battery post cleaner / brush

There is a possibility that the battery itself has a problem.
 
very good article and will keep that in mind. whenever I move back to wi ill be looking over the electrical system very closly. I will be eliminating the ammeter for sure and I knw battery terminals are good as ive had multiple batteries in it and it occored with every battery. so ill be checking the connections at the firewall also as I will be totally stripping the car for body work/mods and paint.

any idea on the denso swap? also can I use the factory brackets (same as what I have on the dart) with a denso alternator? as i have brand new chrome brackets and want to keep em
 
With the ammeter bypassed (best to do it within the engine bay), you will need some type of charging monitor. In my newer cars, I don't like "flying blind", so I use a cigarette lighter plug-in voltmeter. Cheapest is Harbor Freight's w/ an array of LED's (~$4 on sale). There is a way to bypass the ammeter at high current, but leave it functional, using some big diodes. Search for my post on this if interested. Fairly simple, but you need to understand basic electrical design to implement it. Before I used a voltmeter, our 2002 T&C left us stranded with no charge after the serpentine belt started slipping. I got no diagnostics until the engine started missing and the whole dash went crazy.
 
Yes. I bought about 4 of those and use in all my 84+ cars, especially on long trips. I might have bought them even cheaper than the current sale. I can't totally recommend since a diode failed in one of them, though still serves its purpose. Before that, I bought a similar type Eqquis voltmeter on Amazon (~$15) that displays the voltage in an LCD.
 
I have a volt gauge to pot in my day, just have to wire it up, but that's gonna wait till i get my modded dash frame in and the paint/body work is done
 
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