No power when key turned on

[PugDad]

ok, weirdest thing. Rig is 1977, w/ 350. Basic rig, no mods.

I went out to start the truck. No power.

Typically when I turn the key on, the voltmeter kicks up, and the radio turns on. This time, nothing. Nada. Dead.

We had a really cold snap, and I thought maybe the battery was dead.

Grabbed the multi-meter, it showed 12 + volts at battery. I switched to a test light. It lighted up at the battery, would not light up at the positive cable at the starter.

I decided to take off the battery terminals and clean them. When I put them back on, the truck fired right up.

The next morning, the truck fired right up. My wife decided to take it to the store. She called me from the store and said it wouldn't start.

I went down there to check it out, and same symptoms as before..deader than a door nail. I tried taking of the battery terminals and reinstalling again, but no luck.

I took the battery to the shop and had a load test done on it...tested ok, recovered well.

aarrggghhh

Thoughts? I'm wondering if the starter switch got a glitch in it..after all it is 33 years old...