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Electrical issues driving me nuts


hkestes41

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Well I have been having electrical issues with my 37 Plymouth since May. 

Had starting issues early on replaced the battery, starter, battery cables and added grounds a second new starter. Unfortunately, due to my own negligence I didn't get one of the wires to the starter back into the loom clip and it got loose and wrapped around the end of the steering column causing a short and all the wires under the hood to burn up. Luckily I always have a fire extinguisher in the car so it was confined to the wiring. 

Anyway, I rewired the entire car with a new EZ harness and things were looking good once more. Then the electron demons reappeared. Driving down the road on my way home and noticed voltmeter not registering any charge. Made it to the driveway and checked belt good and tight, all wires with good connection etc. Next morning started it with a jump and voltmeter reading 12 volts. So off I go only to look down a few miles later to no reading on the voltmeter. 

Pulled the alternator and had it checked everything shows good. So I swapped out the voltage regulator. Things seemed to be good after I jumped it again and made it home. 

Started the car yesterday again with a jump and started the stopwatch on my phone. A couple minutes after I started it the needle on the voltmeter slowly started falling from about 12 volts and at three minutes and 14 second after starting it hit zero. 

At this point I am clueless as to where to turn next. I am not the brightest bulb in the pack when it comes to electrical and was actually surprised when everything but the brake lights worked after the rewire. 

Is there an internal voltage regulator in a Denso alternator or something else internally that could be heating up and shutting it down? Any suggestions would be appreciated I'm at a loss.

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Denso...what model alternator...look it up by application  if you knowit, by part number if you do not, look on internet for specifics....and if it does have an internal regulator, my next question is why you had to swap out a voltage regulator....you need to list some very specific information on your components to get tailored answers.

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How did you check the alternator?

a simple test is with a volt meter on the battery. Check battery voltage before starting. Should be 12-13v. Start the engine voltage should increase to 13-15 volts. If not turn some stuff on, headlights, radio, heater and increase rpm’s. Should see the increase in voltage. 

I don’t know if a short would cause your charging system to do what you are describing but a charged  battery when you park it and a dead battery next morning will. Plus you did smoke the harness. So, I would check for a short. Remove a  battery cable and connect your volt meter between the cable and terminal. Make sure everything is turned off and doors are shut so the interior lights are not on. With an alternator you may show a volt or two. This would be the diodes in the alternator letting voltage through. It’s normal. To verify disconnect the alternator and recheck. If you still show voltage you can pull fuses one at time to isolate the circuit and point you in the right direction. If that doesn’t work start unplugging stuff. Switches, relays anything connected to the wiring harness until the voltage goes to zero or drops. Just a drop may show one short but if you still see voltage then probably got another one. 

One other thing, since the voltage output from the alternator seems to drop after a few minutes I would perform the alternator test and test for shorts at that time. Not while everything is working. 

 

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Most modern alternators will be internally regulated, Some will have an external diode. If you're running it through the car's original regulator, you're going to have problems.  Also, alternators are NOT battery chargers.  They are battery maintainers.,  Asking them to charge a battery that is almost dead requires them to go to maxl charging  rate and it doesn't take long for them to overheat and burn out internal components.  Pull the part number off the alternator and post it here or enter it into one of the box store's websites.  You should be able to get the specs from their sales info

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