I have a strange electrical issue I'm trying to solve. First of all, my '66 has a number of electrical modifications to the harness. So, this is not for the factory original service manual type answer. Sucks for me.

This has been happening off & on for over a year. The main/original symptom is that randomly(?) (usually when engine is hot) when I key it to start it'll just "click". I had thought at one point or another either I had the starter shimmed too tight, and/or the solenoid was getting low voltage. Today, it did this and I know neither of those is true. The low voltage thing is possible but it would be due to some unknown wiring issue. The problem up until now has been mostly/more when the engine is hot.

Today, the problem seems to have gotten worse. Now, when I key it and it clicks, there is something "sticking". When I key it back to "off", I hear the flasher for the turn signal cycling on/off. I of course checked to confirm my turn signal was not on. So, when I key it to "start", I get a "click", the starter does not engage, and then when I key it to "off" the turn signal flasher is clicking on/off. At that point, I disconnect the battery out of caution.

I have tried charging the battery, disconnecting/reconnecting, removing the starter in case the gear is "stuck" (it's not), adding a shim, confirmed the solenoid gear is not stuck out, etc. After a while of doing those various things, then it will "unstick" and when I connect the battery, I won't hear the turn signal. So, I try to start the engine again and again I get the "click" without the starter engaging, and then the turn signal flasher is blinking again.

Usually, after many hours, and the engine is fully cooled down, then it'll start just fine. It's a regular gremlin. Today, the engine is still warm when I'm posting this. So, maybe later today or tomorrow, it'll startup just fine. But, I need to find the gremlin or else I can never turn it off and park it somewhere and expect to be able to start it later to leave!

Posting here just hoping somebody has experienced something similar and might have an idea where to start looking.

My best idea right now is to remove the starter and solenoid and bench test them, and maybe remove the ignition switch too and bench test it...

 

First thing I'd do is disconnect the turn signal flasher. You may be hearing something else clicking. If it IS the turn signal flasher, you need to find out where the brown wire on the flasher is getting voltage with the key off. It comes from the ignition switch only in the run position. If any of your modifications include adding an emergency flasher or alarm system, you may be hearing that, and you may have a separate flasher. The turn signal flasher is located in a clip right above the driver's knee on the center console above the power antenna switch

 

I should have said; the modifications include but are not limited to:
MSD ignition (eliminates the wire from the solenoid to the distributor)
Powermaster mini starter
I added a relay that takes battery voltage directly to the solenoid when the ignition switch is in "start" position
Other things that I really think don't affect this situation: elec fans, elec fuel pump, elec fans, Detroit Speed headlight kit, internally regulated alternator, ...

still factory: ignition switch

no aftermarket flashers or alarm system

 

I pulled the flasher. I still hear the ON/OFF "clicking" that sounds like a turn signal with the key "OFF". New observation: when I open the door, it stops. Reclose the door, it resumes the ON/OFF clicking. I'm trying to think what would possibly do that. The sound is coming from behind the left side of the gauge cluster, like behind the gas gauge general location. There are a couple of breakers there, I think. Maybe a breaker tripping and resetting? I need to go study the wiring diagram.

I am thinking this is a wiring problem and not a starter/solenoid problem. But why only when it's HOT?

 

Too many modifications to troubleshoot over the internet. Stock had two circuit breakers above the driver's side kick panel (one if you don't have power windows) and the other is for the headlight rollover motors. Feel and see which one is clicking. Stock would have 12v to both with key off. Whichever one is clicking has a short in it's circuit and it's resetting as it should. Probably running the battery down, too.

 

Actually, you've helped me. I have a plan of attack now. Disconnect the two systems on that breaker, check out the IGN switch, bypass everything and put 12V on the solenoid, go from there. I just hope the gremlin didn't damage another component or system while it was running around...

 

If you only have one breaker, one red wire goes up to the red wire connection on the horn relay and the other side goes directly to the headlight rollover switch. Again, that was on STOCK setup. The Detroit Speed conversion may have removed that from the circuit. The headlight rollover switch was definitely not used with the conversion and most remove it completely. If it didn't, maybe the wire is hanging out and touching something and tripping the breaker. You don't need that breaker for the conversion, but I left it in and connected the supplied fuse in line to the DS control bd. Follow the red wire that attaches to the breaker and you'll find where it was in a connector with three wires that previously went to the rollover switch. It's 12v all the time the battery is connected. Make sure it's not touching something