I have (had?) a problem in my '67 where it suddenly started blowing the ignition fuse (10A) every time I switched the key to "ON". It would still crank but obviously never kick with the fuse gone. Replaced the fuse a couple times and each time it would blow.

This happened once before but as soon as I determined it was a blown fuse and replaced it things were fine. This time it was more constant.


So I removed the fuseblock off the firewall to check for any issues there. Some of my contacts are pretty well rusted but I didn't see any evidence of chafing or stray filaments so I put it all back together and tried it, still blowing the fuse.

I took the ignition switch out of the dash (with much difficulty, I have big hands!) and checked things there, all looked OK. I buzzed the IGN wire from the switch to the fuseblock and that seems good as well. I couldn't find a connection diagram for the switch itself but I tried my best to buzz it out and didn't see anything ridiculously strange (IGN and GND weren't tied together or anything)

Just for giggles I plugged the switch back in, still dangling from its harness under the dash, and this time it started right up! Hmmmm....

Makes me nervous, obviously. I'm thinking that since it's happened twice and each time it was while I was trying to start it, NOT while it was already running, it may be the switch itself rather than some possible harness problem further up in the dash.

Any thoughts on this?

Do you have the original points distributor or an HEI? The HEI requires a little more current. 10 amps might just be at the edge. You could up to a 15 amp without any issues. If you actually do have a short a 15 amp would still blow before melting any wires. Another option is use 10 amp slow blow fuse. It may be that initial surge when you turn the key on that is blowing the fuse. A slow blow will survive the initial surge but blow if the current continues to exceed 10 amps.

It does have an HEI, but in desperation (because it left me sitting in a parking lot!) I tried a 20A against my better judgment and it also blew.

It got a ride home on a rollback, I was bummed.

It does have an HEI, but in desperation (because it left me sitting in a parking lot!) I tried a 20A against my better judgment and it also blew.

It got a ride home on a rollback, I was bummed.

Well in that case I guess it could be switch. Could also be under the hood, HEI power feed wire shorting somewhere?