Boy, this sounds so vaguely familiar to a problem I had with a Z ignition once. I remember subbing out several ignitions that I had on hand and was incredibly frustrated. Turned out, the solution was something real simple, like I installed the connector 180 degrees out or something like that.

10 hours ago, Patcon said:

when turned to lock still has power going through it and some times it will bump the starter if it's returned to lock too fast. I have taken it out and tried a different switch but I am getting similar results.

Could you distinguish the mechanical part of the switch from the electrical part? You showed three assemblies of mechanism and electrical switch so I'd guess you just unplugged each and plugged in a new one, then turned the key. But it's not clear.

Hard to see how three different assemblies could be a switch problem. Seems more likely to be shorted wires in the harness.

Anyway, here's what I mean by electrical part. You can manipulate it with a screwdriver. You might take your switch apart and give it a twist.

Edit - I'm not sure if it's possible but I could imagine a scenario where the mechanical part allows the electrical part to over-roate backward and hit Start. Don't know. The mechanical part is just a long thin rod that fits in the slot to turn it. I had to give mine a bend to get it to turn far enough, when I had some starting problems.

https://zcardepot.com/products/ignition-starter-switch-240z-260z-280z-510?

Edited July 19Jul 19 by Zed Head

When we started we substituted a different switch on the back of the installed mechanism. Same result. Then I found my box of switches and tried two more. They all do it, but there are oddities. The brake light doesn't light up at first, but after I cycle the switch it stays on in the lock position. I'm unsure where to go from here. I will try the switch loose, maybe tomorrow, but I'm not sure if the detents are in the switch or the key mechanism

Edited July 19Jul 19 by Patcon

On 7/18/2026 at 8:19 PM, Patcon said:

When we started we substituted a different switch on the back of the installed mechanism. Same result. Then I found my box of switches and tried two more. They all do it, but there are oddities. The brake light doesn't light up at first, but after I cycle the switch it stays on in the lock position. I'm unsure where to go from here. I will try the switch loose, maybe tomorrow, but I'm not sure if the detents are in the switch or the key mechanism

Switch. Pull the connector off the stock switch, plug it into the spare switch, use a flatblade to turn the switch.

So I received a brand new ignition switch. Just the rear switch portion.

Attached like so, with no key mechanism

Turned it with a screwdriver

No brake light until I bumped the starter. Then the brake light was on. When I turn it back quickly to the lock position the car continues to run, although poorly, and the brake light is still on

I suspect the accessory relay but I don't even know where it is. I'm unsure if there are any other relays that would need checking

The accessory relay is on the right side above the passengers knees. It shouldn't have any impact on ignition, but if you want to disconnect it to see if the issue goes away, you can do it like this. Note the disconnected four wire connector at the bottom of the pic:

:

And just to simplify matters, try pulling the top three fuses in the left column. They also should have no impact on ignition. The car should run without them. Pull the fuses marked Air con, Wiper, and Flasher:

Just looking for experiments that would help diagnose what's going on.

The only other place I can think of that will turn on the brake light in the speedo is the brake warning switch.

How about the voltage regulator? It has moving points that could get stuck. Maybe it's backfeeding in to the ignition system.

The brake light in the dash should light when the key is on, engine not running, but go off when the engine is running. I think that that is also controlled through the VR.

Should start and run with it unplugged. Maybe you'll get lucky.

Edit - actually I'm not sure what it will do if you unplug it. Have to study the wiring diagram. If you have a spare it might be worthwhile to swap it.

Edited July 23Jul 23 by Zed Head

My car does exactly this, but has an EZwiring style loom. I've assumed its being backfed from the alternator by the excitor or sense wire and I'll need to add a diode somewhere.

I've not bothered to do anything about it yet.

Edited July 23Jul 23 by jonbill

You should be able to disconnect any possible back feeding of the ignition system if you pull the third fuse down in the left column. The one labeled "Flasher".

If power is back feeding through the voltage regulator, the gauges will still work and the brake warning lamp should stay on, but the engine should die because the ignition circuit will have no power.

@jonbill , @Patcon ,

I was poking around with an ignition switch and a meter and found the following anomaly. This is probably related to the "running in the LOCK position" issue you have seen. I cannot identify the smoking gun on the wiring diagram that would exactly cause the run-on issue, but I wanted to throw this out there so others could be aware and maybe come up with some theories.

Due to the internal construction of the ignition switch, there are (undocumented) two pins on the switch that get connected together in the LOCK position. Wire colors are B/W and L/R. This is not shown on the wiring diagrams. In theory, it doesn't cause any problem on a stock electrical system, but in reality on a non-stock system, who knows. Here's what I'm talking about: