Diagnosing an Alternator or Voltage Regulator

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portnoy

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Hello, I'm having issues with my 1983 Plymouth Scamp GT.
Had the battery die, got a jump and it worked. Died again, jumped again, battery tested at 9% power, replaced battery. During the second round of dying, the lights stopped working, and tachometer was reading at least 1k rpm low.

Since the battery was replaced, it died two-three days later.
I have had it on an overnight trickle, seems to be resting at about 12.7 volts. A reading with the car running at 1500 or 1000 rpm is 12.66. With the lights on, it is 12.4 and slowly dropping.

My guess is the alternator. I looked for parasitic drains first, but had no amp draw (or .02, something small) so that was ruled out. A new alternator is only about $40-50, so I'd love to avoid the shop diagnostic fee and installation fees.

Belts are tight, though the alternator itself has a shitty mounting system and tends to travel 1/2" loose on the screw over time, with its high quality tattered plastic bushing. After tightening, the problem remains.

Any ideas what to check next, or does this sound right?
 
Get the alternator tested sounds like 1 phase of the stator is out. OTC used to make a charging system tester with 2 or 3 lights on a 2x3 inch box with 2 leads 1 ground and 1 to put on the output lug on the alt and it would tell you if this was you problem. They will charge but very marginally.
 
bcschief said:
Get the alternator tested sounds like 1 phase of the stator is out. OTC used to make a charging system tester with 2 or 3 lights on a 2x3 inch box with 2 leads 1 ground and 1 to put on the output lug on the alt and it would tell you if this was you problem. They will charge but very marginally.
Click to expand...

Not sure I agree, but I'm no longer familiar with these cars. Been more than 20 years already since I had the old Dodge 600, or my Grampa's K car

To the OP.........you have or have a link to the basic wiring on these cars? I used to have a K car manual or two, but...................
 
I would check that the regulator has ignition supply, ground at case and connection to field. The other field connection hooks to ignition supply. Use your meter. There should be several volts measuring across field terminals. If there is, alternator may be bad, if no field voltage then wiring or regulator problem.
 
Swapped the Voltage Regulator... everything seems to be working fine! glad it was such a simple and inexpensive fix
 
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