Won’t start

...GROUNDS!!!!

MJ

I know, I agree. I just don’t know why all of a sudden a ground would fail. Unless, of course, what you’re suggesting is something has grounded out.

...if You jumpered the Battery +, bypassing the Ign. Switch, and there is Still 'Nothing' activating...in My view, It can Only be 'A' Ground(s) is/are Not Grounded.

Get out the Volt/Ohm Meter and Check for 'Continuity' with ALL Grounds, Starting AT the Negative Battery POST and going to All Groundings!

Good-Luck with it!

MJ

...and realize, the ONLY Ground the Engine Block has, is that spindly strap at the Tail of the ZF Transaxle!! Myself, Years ago, I added a 'Beefy' Ground Cable Directly From the Frame To the Starter Motor Case. This may Not fix, in Your case, but it will surely Help the Next time You try to Start the Engine.

P.S. Grounds are Always Coming Loose on these Panteras! Check the 8-10 Ground wires going to the Stud on the Chassis UP Deep, and Under the Dash, AT the Left Corner above the Drivers' Left Knee. You'll need to lay on your back and use a Flashlight, to find them.

If I was looking for a 'Positive' Disconnect...I would Inspect the Connections on the Back of the AMP Gauge. It's common, These come loose, because of the High Heat! And second, the Junction Block at the top of the steering column, behind the Steering Wheel, wires can 'Pull-Out'.

I think that the ignition switch is the likely culprit. The internal spring loaded pins are freezing in the open positions.

After 50 some odd years the grease dries up into a glue.

Well, I will say that today was the biggest workout the ignition switch has had in years …literally.  I need to get my ohm meter, test the four wires coming into the switch for power, and likely go from there.

Novice question - Can I disassemble the switch, clean it, and rebuild it?  Or, am I destined to spend the money for a new one, assuming that is the issue?

I would start by removing and cleaning both battery cable connections. Clean the inside of the cable clamp and the outside of the battery posts.

Yes, the switch can be taken apart and refurbished. Save that for your last option.

confirm you have 12 V at the starter relay. I don’t know the testing process you used to bypass the starter relay but if there is voltage there and the relay is good, the starter should engage with proper jumping .

however, Jon Haas has recently shared with me that he is aware of brand new starter relays being DOA out of the box.

Larry

I'm with Forest on this one. The fact that you don't even get fans (and I assume lights?) indicates something common to all. Has the new battery been load tested?

Well, lump me in with the people who have experienced the simplest of problems and taking the most complicated of routes. The negative lead/ground on the battery was apparently 200 years old, presumably off a model T Ford, and was worn thin under the collar. Replaced and problem solved. I think you all, the collective Pantera community, once again.

👍👍

I love a happy and easy solution to electrical problems

Larry

Right.......Like I said, Also, be sure to inspect the Ground 'Cable' at the Tail of the ZF.

Be Happy You did Not pay a 'Professional' $140.00 an Hour to troubleshoot for a Bad $7.00 Cable!

...And, be The Most Happy, this Fail, did Not happen out in the Desert, "...In the Middle of Nowhere".

MJ