Generator Light

Generally voltage regulator or alternator. Could be loose belt too.

I had to have my alternator rebuilt and now the light does nothing. I was told that the power for the light, when the engine is not running, is internal to the alternator.

Can I check alternator/battery with this simple device!?

I get readings of 16.8-19 after idling 20 min with car on

 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.

Hi David

Tested another pantera at the battery without starting car got roughly same voltage around 17 or so

Think it's my meter that off?

My ammeter gauge needle bouncing wildly but I dont know if that's related?

That should not happen.  I have no idea. Do not ground out the amp gauge as that will destroy it, $200.00.

The posts should be protected.

Dick Ruzzin

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

WarrenVictor,

as for your DMM displaying higher than expected, I wonder if that "battery" icon on the left is an indication the battery in the meter is low and needs to be replaced?

I was looking for instructions for that meter and found this on how to "calibrate"

https://youtu.be/mk7CmhrJokA

Excellent observation!!!!!!!!!!!!!!!!

Thank you all for your great input!

I changed battery in meter and made a difference.

I get 12.7V at battery and 14.7-15.3V (reading fluctuates) while engine runs!

My other car reads a solid 14.72V(no fluctuation) while running.

What do you all think!!??

Thanks

Warren 

JFB has excellent powers of observation!! 

 Thrilled we all learned something and a happy out come.

Yes David, But let's get back to my question....Are my readings in the normal range? And why does the meter read (bounce) between 14.7 and 15.3 while car is running instead of a solid solitary reading?

And if readings are normal why is gen light in dash blinking on and off!!???

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

Thank you JFB!

I would have to check on the alternator/regulator to see.

Car was totally nut and bolt restored by Dennis Quella at Pantera Performance in late 1990's prior to my ownership.

I will check restoration receipts to answer your question.

Your thoughts?

the G/R wire from the alternator to the S terminal on the regulator is poor connection OR the "switch over" in the regulator gone bad.

the volatage swing sounds like something the mechanical regulator would do normally, where as a modern solid state would hold voltage smoother

Hi JFB

receipt says Alternator OEM type and voltage regulator 1997

Only 1000 miles driven since resto!

Thoughts?

Thanks

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