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I have an 86 Dodge ram 3/4 and I'm having charging issues. My alternator went out about a month ago. Bearings and such. Purchased a new one and truck worked fine. I use it for mainly plowing. A couple.weeks after it stops charging again. So I check and was getting volts from all three terminals on the back of the alternator. So I assumed it was fine and purchased a new voltage regulator and everything seemed fine. Plowed the driveway and the other day started the truck several times no issues. Go to plow and suddenly starts losing voltage. Plow won't go up . Wipers going slower. So I check the alternator and I get volts from two terminals but not the main one. It flashes 19-20v for a second and won't read anymore till I keep poking n rubbing the multimeter leads. So I bring the alternator in and get it tested. They say the alternator is bad. Failed all the tests and putting out 30+volts so I put a new alternator in again and start plowing and soon I'm dead again. So I do some checking and getting 12 or so volts out of two terminals and none on the main again. I do some research and come across a video on regulators and the guy shows using a multimeter reading ohms from the two leads from the voltage regulator. His read 1.7-1.8 saying that's about 14.6 volts. I check both my old and new regulator and I get 17.6 ohms. I recheck the alternator and this time I'm getting 8-9v and watch it slowly dropping on the main terminal . So after all this long ass message lol. Sorry about all that or if it's confusing. I'm wondering if I need a new alternator and new voltage regulator. My alternator is just a stock 60amp. Or if I can upgrade to a different setup or bypass anything or burn it to the ground as an option?
 

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I would consult an Auto Electric shop in your area

I don't believe that 60 Amp alternator is even close to what you need for a plow & related lights

you didn't mention what engine you have in your truck
 

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On your alt. there should be 4 connections (if I am not mistaken) a ground, + battery, and the 2 fields.


Ground should be a good ground reading - ie. zero ohms from that terminal the neg. battery terminal.


+ battery is the cable going to the battery and should read + battery voltage at all times.


The 2 fields are what controls the alt. - One is + batt. voltage via the ignition switch and the other is a ground control from the voltage regulator.


The voltage regulator has a + wire coming into it via ign. switch and the alt control wire going out to the alternator AND MUST HAVE A GOOD GROUND. If the voltage regulator is not grounded it will not work.


I think this is how it works but it has been over 20 yrs since I worked on this system.


It is a simple system over all. Over voltage is usually a bad regulator - but it could be an internal short in the alternator (not common though).


Under voltage has several reasons for not happening.
Open regulator
bad alt diodes
bad regulator ground
bad alt. ground
bad + wire from alt. to battery - this wire may go through a fuse link between the alt. and battery. - I am pretty sure there is a fuse link but am not 100%


So, I would check.
Key off - (+ battery voltage at + alt output), (good ground at alt, zero ohms between alt ground and - batt terminal ), no voltage at either field terminals.


Key on running - (+ batt voltage at + alt output), (good alt ground), ( + batt voltage at one field and less than battery voltage at the other field).
If you ground the wire coming from the regulator to the alternator for a few seconds you will full field the alt and get max output - so you should see a higher voltage at the battery + terminal. Only do this for a few seconds and make sure you get the right wire off of the voltage regulator - if you unplug it from the regulator you should have + battery voltage on one wire and I think zero voltage on the other ( or at the very least less than + voltage). Or if you want to be positive, with the key off and the plug off of the regulator, just ohm out which wire goes to the alternator.


Make sense?
 
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