Weird electrical issue affecting almost everything in the dash

[MaximRecoil]

Today I came out of the grocery store, started my car (1969, 318 engine, 904 transmission), and as the engine started I heard a weird noise, like a snapping sound, and almost everything in the dash went dead: the gauges, the radio, the windshield wipers, and the blinkers (I didn't think to try the headlights). The only electrical thing in the dash that still worked was the hazard lights.

I drove home, which is a few miles, and everything stayed dead the whole way. I took my groceries into the house, went back out and checked all the fuses and fusible links with a continuity meter, and they all tested good. Then I started the car and everything was working again.

What could possibly cause that? If a wire had broken or a fuse had blown, it obviously couldn't have fixed itself. Are there any self-resetting circuit breakers (such as a "thermal fuse") in my car that I don't know about? The only one I know of is in the headlight switch, but when that trips, it only makes the headlights go out. I had that happen 8 or 9 years ago, the first time I drove any distance at night, and I put the headlights on relays a few days later and never had another problem with them.

[70 sublime]

Did you check the main plug that comes through the firewall ?
Anything loose or half melted ?

[MaximRecoil]

The bulkhead connectors are fine, and a couple of weeks ago I cleaned all of the brass Packard 56 terminals in the bulkhead connectors with electrical contact cleaner. I've been driving it every day this year for the last few months and this is the first time I've seen this dash issue.

It does have an RTE Limiter IVR4 (https://www.rt-eng.com/index.php/RTE_limiter.html) in place of the original electromechanical 5-volt regulator for the gauges, which I installed about 7 years ago (and I've never had a problem with it), and according to their website, it has a "built in polyfuse" (AKA: resettable fuse), but if that had been tripped it should have only cut power to the fuel, water temperature, and oil pressure gauges, but the radio, windshield wipers, and blinkers, all of which run off 12 volts (rather than through the 5-volt regulator for the gauges), were also dead.

And when everything came back to life upon starting the engine again, I hadn't reseated, wiggled, or otherwise touched any wires or connectors, aside from touching the fuse terminals with the probes from my meter to test continuity.

[Nacho-RT74]

It seems all the sources you are mentioning comes from ACC source ( engine still kept running, right? ), so I would point out to the ign switch missing contact with the ACC points inside. The ign switch phenolic piece could be getting loose from the pot metal assembly and point is loosing contact ( althought ign1 still in touch ) OR ACC point itself into the switch got worn.

Hazzard comes from batt source so is not feed from ign switch. Headlights too.

[MaximRecoil]

It seems all the sources you are mentioning comes from ACC source ( engine still kept running, right? )

Yes, the engine ran fine despite the electrical stuff in the dash not working, so the ignition switch was definitely allowing power through to the ignition system.

so I would point out to the ign switch missing contact with the ACC points inside. The ign switch phenolic piece could be getting loose from the pot metal assembly and point is loosing contact ( althought ign1 still in touch ) OR ACC point itself into the switch got worn.

Hazzard comes from batt source so is not feed from ign switch. Headlights too.

The ignition switch was in the run position, not the accessory position, so if the accessory position in the switch is going bad, how would that affect anything when the switch is in the run position? Is it a double-pole switch, i.e., when in the run position both the run and the accessory terminals are closed, and the stuff in the dash always relies solely on the accessory terminal for power? If that's the case, then I bet the ignition switch is indeed the problem. I've been meaning to replace it for a long time because its mechanism has long felt gritty and sticky when you turn the key. For example, I have to manually turn the key back to the run position from the start position once the engine starts, because it doesn't spring back on its own very well like it should.

[XH29N0G]

Maybe this is me being paranoid, but I disconnect the negative post on the battery when I am not driving the car.  If I heard a snap and the dash shut down, I would be looking to trace it using the wiring diagram from the FSM and at the same time have an extinguisher near due to worry that there might be a short that could start a fire.  I wish I had a more specific suggestion and apologize that I don't.

Hope you find it and fix it soon.

[Gold Rush]

Nacho is spot on regarding the "Accessory" output from the ignition switch.  Internally the switch is configured so that output is active in both the Run and Accessory positions.  Of course, when the switch is in the Accessory position those outputs present in Run are not enabled.

From what you are saying, it sounds like time for a new switch... 

[Nacho-RT74]

ACC and Ign1 are two diff circuits on diff terminals and points inside the ignition switch no matter the stage of the ign switch, hence my conclusion.

As mentioned in ACC just ACC is sourced. In RUN both Ign1 and ACC are sourced. In START, Ign2 and START to the starter relay are sourced, that's the reason why ACC is cut while cranking.

Also in START the Ign1 circuit is sourced but just because Ign1 and Ign2 are linked by the Ballast not from Ign switch, and that's why the Brake light ( and oil light if standard cluster ) dims out while cranking. That's one way to know the Ballast is good or bad in fact. ( along with the Ign1 circuit wiring )

[MaximRecoil]

Nacho is spot on regarding the "Accessory" output from the ignition switch.  Internally the switch is configured so that output is active in both the Run and Accessory positions.  Of course, when the switch is in the Accessory position those outputs present in Run are not enabled.

As mentioned in ACC just ACC is sourced. In RUN both Ign1 and ACC are sourced. In START, Ign2 and START to the starter relay are sourced, that's the reason why ACC is cut while cranking.

That makes sense; thanks.

Are aftermarket ignition switches any good, or should I look for an original one? Also, it seems that the 1969 ignition switch was a one-year-only switch. What's different about it compared to e.g., a 1968 switch?

[Nacho-RT74]

Yes, one year only. The key cylinder is bigger on 69 than previous years. Since 70 was changed to the steering column.

As I told, the phenolic piece could be loosen from the metalic housing and just will need to be tightened again. They fit by pressure.



Dunno on aftermarket switches, but usually they are not with two ign stages like Mopars are made to the ballast bypass.

Give the chance to the checking, you could fix both issues at the same time ( ACC and the returning )

[Nacho-RT74]

[MaximRecoil]

Thanks for the information and comparison picture. I ordered an NOS Mopar ignition switch. I don't know about removing the old switch and lock though. I assume there's a special tool for removing that threaded ring/nut that secures the switch and lock into the dash, but I don't have one. I wonder if I can loosen the ring with a hammer and screwdriver without damaging anything. I've removed an antenna nut that way before, which is the same idea.

[Nacho-RT74]

You should be able to do it just like the antenna bezel

[MaximRecoil]

I replaced the ignition switch today with an NOS Mopar one, and getting that slotted nut off was the easiest part. I just tapped it counter-clockwise with a hammer and screwdriver. The rest of the job was a lot harder though, because there wasn't enough slack in the wiring harness for me to pull the old switch down below the dash, which made it very hard to get the plug off of it (which is clipped onto the switch on both sides). By removing the entire ashtray assembly I was able to get my hand in behind there from the side to grab the switch, and with my other hand I used a screwdriver through the switch's mounting hole to undo the plug's clips and push the plug off.

In any case, the new switch is in and works great; much smoother than the old switch when I turn the key, and it springs back to the run position from the start position perfectly.