OK, never had any problems with the '72, until Friday. After some spirited "testing and tuning", I park for a minute in the driveway, and when I return 5 minutes later, no start. I mean no crank, no click, nothing. Voltmeter says 12.65 volts, battery OK. I even hook up the charger just in case. NO Go. The voltmeter drops to 0.35 volts when I put the key in the ignition, not turned or anything, just slipping it into the key cylinder. The buzzer sounds for about 2 seconds and everything dies. No headlights, no nothing. 2 hours later.....varooomm! It starts like nothing, and will restart on demand. Next day, varoommm, runs for 5 minutes in driveway, then WON'T start again!!! I'm thinking "heat soak" in relation to the starter. BUT it won't start this morning either, just dead! Battery is OK, but nothing works. All the fuses are OK, and the buzzer, seatbelt warning, and the parking brake light all came on intially, but after the first turn of the key, all went dead immediately. What is going on??????? :crazy:

 

I would check your major connections on the car for being loose or having corrosion. Both battery terminals, ground connection on chassis, connections at starter and horn relay.

 

OK, you are going to need a good voltmeter, a decent DVM...digital volt meter....and you need to have the tning in failure mode, and then say turn on the headlights, and look for missing voltages....but n the meantime, just for to be sure....
you need clean all the battery terminals on the battery and the cables...if you have those replacement clamp on terminals at the cable battery ends, be super suspicious of them...look for green or corroded or melted insulation....and wire.....

after that, go under the battery box and fine where the negative lead attaches to the frame, pull it off , clean everything in the area down to bright shiney metal...get a new star grounding washer, clean up the bolt, and resecure everything....NOW under the pass side engine mount, you will find a 6" LONG HEAVY battery cable, going from under the engine mount bolt to the bolt on the frame close by.....pull and clean everything down to bright metal once again.....

NOW, again on the battery post of the starter, do the same cleanup routine...
if all this cleanup of corrosiion doesn't help....try us again on here...at that point you will need a voltemeter.....

hold on, you may try wiggling the bulkhead connector under the master cylinder.....I doubt it, but maybe.....
check also for unusual water/moisture under the driver's side, fuse panel corrosion, and or maybe a bad connection on the steering wheel switch...on top of the wheel, where you need drop the column to get to it....

GENE

 

Yikes, I feel like a Rookie! Yep...the battery cable clamp was the problem. 2 minutes of "work" to clean it up and re-clamp, then reattach to the battery, varooommm. Possibly the problem, but it has acted like this yesterday. Hopefully this is it...and thanks for the advice! :hurray:

 

My similar problem turned out to be some chafed wires that went through the firewall from the ignition switch. Unfortunately, I had some idiot mechanics who replaced the starter motor four times .... thinking each time it was a "bad one". They also replaced the ignition switch thinking that was bad. One mechanic even replaced the alternator....twice. As I said...it turned out to be a chafed wire that was shorting out as it touched the hole in the firewall. This problem went on for about 12 years.....and I don't even want to say how much it cost.....

 

Man I am having the same problem so it makes me feel a little better to know I'm not alone. I have had my starter rebuilt, got a brand new battery with 1050 cranking amp capacity and I cleaned all my major electrical connections. It seemed like when the engine was really hot it wouldn't start until a few days ago it wouldn't start after sitting for three days. Looks like its time to go short hunting... :rolleyes: