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Positive ground 1959 Triumph TR3A - polarity issue?

Do I have a Parity issue??
Car has been starting and running fine for sometime. I would drive car around once a week for 5 miles or so. Two weeks ago I started the car and backed it out of the garage. I turned her off and went inside for a moment, when I tried to start the car - when I turned the key I noticed the AMP gauge jump as usual, however when I pressed the start knob I just heard a click. I placed a multimeter on the battery it showed 10 volts so I removed the battery and put it on a trickle charge over night.
The next morning I replaced the battery - I turned the key turned on the lights to confirm that they were working then I tried to start the car, just got the Click then nothing. I turned the key OFF the back On - the AMP gauge did not move. Checked the battery it showed 12.5 volts.
Lights do not come back on. Only after I remove the leads from the battery for a few minutes then reconnect - can I actually get the lights and the AMP meter to jump, but will not start. Just get a click
Two items in question:
1 - when I first reinstalled the battery after the charge - I foolishly healed a wrench in my hand which made contact with the NEGATIVE post on the battery and the metal battery hold-down clamp - Which made a SPARK
And 2 - when I turn the key to the ON the AMP gauge jumps to the Negative side.

Thoughts?

Hi Joseph,
I’ll start this by saying I am not a TR3A expert. I have spent quite some time with 12V electrics. That being said, I’ll try to help as best as I can.

Just to clarify - the gauge in the dash is AMP and not Voltage, correct?

1 and 2 - My assumption is the sparking wrench caused a current spike in the amp meter. Those old meters are somewhat sensitive.

My initial assumption for the no start issue is poor grounding. It sounds like you have a voltage meter, so here’s how I would test things. Have a friend in the driver’s seat and check voltage at the battery. Have the friend try to crank the engine over while you’re testing voltage at the battery. If it drops significantly (below 10V or so), you may have a bad battery. If it doesn’t drop by much at all (stays about 12.5V) you may have poor connection to the starter. If you can reach it, it’s worth checking voltage at the starter. Check with key on, then also check while cranking over. If it’s crazy low, I’d be looking at grounds and perhaps even the high current negative line from the battery.

For starts, I’d trace the grounding straps and see how the connections look. Are they rusty or green/white from corrosion? Are any of the ground cables bulging near the connections? It’s worth thoroughly cleaning all of the grounds on the car, even if it’s just preventative maintenance.

Thanks for the info. I will double check the connections
Confirmed - AMP gauge is reporting amp’s
Battery is new and strong at 12.5 volts
The cable connection for the Negative poll on battery is mis-shaped, may not be making a full connection. I will find a replacement.

One observation with my multimeter regarding the Key/switch on dash for start.
I have continuity 12 volts between the two connect on the back with the key off. When I turn the key on - I get no reading