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 16,8 is too high a voltage.  Your harbor freight meter might not be accurate. It is safe to assume you have another vehicle , test that one.  14.7 at the battery would be OK.  Then you can determine if your meter is off or the Pantera alt is over charging.  

   You did not say if you are still running the stock alt or you have up graded.

  A loose connection or high resistance in the alt / reg  ground circuit can cause strange voltages.  Start there rather than throwing parts / money at the problem.

   Most major auto parts stores can test the alt if removed from the car.  My gut feeling would be more likely around the regulator.  The first regulators were mechanical , the later solid state should fit without rewiring. I have no idea when Ford made the switch to solid state.

   I would expect a bad alternator to under charge  rather than over.

  If the alternator was trully bad consider a late model internal regulator in the 100 amp range. That does open the can of worms of up grade the amp meter in the center sub dash.  The amp meter handles all the current in the system and can be a fire hazard.  There should be plenty of information on this forum on that subject.

I have the same harbor freight meter as a part of my survival tool kit.  Mine  reads close to a commercial Fluke meter. I got lucky.

 The Pantera amp meter is known to bounce around alot.  That is also covered in the threads of the forum. 

  I changed gauges to Auto Meter and the amp meter is now a expanded scale volt meter.  I feel the information is more relavant.

   Still would not hurt to make sure connections are clean and secure.

   The front compartment has a stud welded to the chassis for a ground connection. The engine has a ground strap at the rear of the transaxle. The voltage regulator (stock one) is in the right rear wheel well ,  could get wet and corroded connections.  There is also a common ground stud under the dash that can be problematic. I would think the under the dash ground would affect things in the cabin and dash mostly.

   Panteras are known to have electrical problems.  This forum is a wealth of great information.

  Without starting the engine and no load I would expect more like 11.5 to 12 volt with a well charged battery. Starting the engine at curb idle the voltage should climb to 13.5 to 14.7 volt.  

  Harbor Freight also has a automotive test device that has a series of leds that show approx. voltage.    A whole $4.49.

  https://www.harborfreight.com/...ry-tester-63592.html

12.7 VDC is good for just the battery

14.7  running is good, showing the alternator is charging

the swing and the lamp on . . .  not good

did you ever say if you have the original "mechanical" regulator, or a solid state, or even a built into the alternator

 

here is a drawing of the original charging system, showing the intial energization of the alternator field through the lamp and then the switch over to self excitation once spinning.  notice the relay that uses the center tap of the stator 3 phase windings

 

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Last edited by jfb05177

my "WAG" is purely based on an acadimic view of the drawings. . .

for the intermidiant lamp,

Loose wire possible (in no particulair order)

the Y wire from starter relay to regulator A

the G/R wire from the alternator to the regulator S

there could be loose wire internal to regulator causing the voltage on the G/R wire to faulter

the transfer relay in the regulator going bad

 

as for the swinging output voltages. . .

this seems to be common for original as indicated by amp meter.   I really wish i was in my prime and had access to investigae this condition as it seems to be the type of problem I enjoyed solving.  my guess is it could be midigates with the addition of filtering the stepping field current generated by the mechnaical regulator.

 

If a solid state, then the regulator is going bad as I would assume field current stabilization is part of that design

 

given these are just my wild arse guesses, I will bow to any others comments

 

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