I believe the cluster grounds through the screws holding it to the dash.

Studying the wire diagram a bit further, I don't see how the Dash gets 12V from the IGN-1 key position unless IGN-1 grabs its 12V source from the ACC circuit inside the ignition switch. is that correct?

The accessories are fed from the ACC terminal on the ignition switch. That is energized in the ACC and Ignition 1 positions of the switch. You are correct, the master splice of the black leads from the ACC terminal are the feeds to virtually everything in the car that isn't individually fused.

I find it interesting that you said "When turning the key to ACC, the test light flashes but it doesn't when the key is switched to IGN 1. Looking under the dash, everything appears to be stock and in its proper place with no apparent splices. The IGN1 circuit to the dash eventually starts working after 5-10 minutes so maybe a bad circuit board ground?".

In this 5-10 minutes do any of the other accessories like the windshield wipers and turn signals work? That would prove if the splice is being energized initially. I am assuming that initially the test light does not flash when the key is in IGN 1. I do not think it's a ground problem. If it were a ground problem the IVR would not be functioning in ACC.

Mattax, I traced the G5 wire (referred to as P4 18DBL* on 1969 Charger Wire diagram) and it goes to the brake warning lamp. See attached. Looks like the 12V dash feed comes from the Black Wire node splice, no?

Studying the wire diagram a bit further, I don't see how the Dash gets 12V from the IGN-1 key position unless IGN-1 grabs its 12V source from the ACC circuit inside the ignition switch. is that correct?

I also hooked up a test tight to the temp sensor lead at the front of the block. When turning the key to ACC, the test light flashes but it doesn't when the key is switched to IGN 1.

...
I find it interesting that you said "When turning the key to ACC, the test light flashes but it doesn't when the key is switched to IGN 1. Looking under the dash, everything appears to be stock and in its proper place with no apparent splices. The IGN1 circuit to the dash eventually starts working after 5-10 minutes so maybe a bad circuit board ground?".

In this 5-10 minutes do any of the other accessories like the windshield wipers and turn signals work? That would prove if the splice is being energized initially. I am assuming that initially the test light does not flash when the key is in IGN 1. I do not think it's a ground problem. If it were a ground problem the IVR would not be functioning in ACC.

6Pak - With the ignition switch hanging down under the dash, I was able to jiggle and push/pull the harness plug in the back of the switch and got the test light to flask in IGN-1 position. More evidence there is an internal short or something going on with the switch. Blinkers worked at all times. I see that the 1969 ignition switch is one year only and made of unobtainium. Classis Industries sells a reproduction switch made by Max Performance. Anyone have any experience with these?

There is something odd here. The turn signals are fed with wire D1-18BK from the master splice. The IVR for the gauges is also fed from this master splice on wire G1-18BK. How can one work initially without the other? The gauge issue seems to be changing to an instrument cluster problem. I would once more recommend checking the voltage at the temperature sensor immediately when the gauges are not working. If your test light doesn't flash, I'm going to put my money on the IVR. How do the wipers respond initially?

Ah ha!!! It sounds like you have isolated it to the switch. It still seems odd that initially it won't work but after a number of minutes it will. I am struggling with what can cause that. But as Thoreau put it regarding a trout in the milk, what you have is what you have. Good job!

Those are definately possibilities.
I'd go with a trust but verify approach.
1. Remove the connector from the key switch. Check continuity from B to the other terminals with key in every position. Using resistance setting on the multimeter would be best.
2a. Check for continuityand wire colors between the connector cavity that matches I1 and the G1 wire terminal at the board.
2b Check for continuity and wire colors between the connector cavity that matches A and the G1 wire terminal at the board.


Once the wiring is sorted out, that shoudl take of the starting issue and hopefully also the gages.
But if the gages still have an issue, even though the other 'accessory' are working immediately, then its probably a connection on the board.
This is an instance where the voltage can read OK during testing, but doesn't reveal resistance. The resistance only shows up as a voltage loss whith sufficient current flowing through,
This can happen with the main feed as well, in particular with the 'MAD' approach. The battery is first in line from the alternator output. That could make the battery the path of least resistance back to the alternator's ground. If the distance and resistance to the rest of the circuits is long enough, high enough, then they don't get the full power until the battery is recharged.
I don't think that's what's happening here. The switch or its connections seem to be the culprit, or at least the main culprit.

electrical problems are the reason there is no hair on the top of my head.................

Could also be a bad crimp/connection
As for the warm up time, excessive resistance, again switch or connection.
I would first inspect that terminal and crimp very thoroughly, post a pic if you'd like

if it is in fact the switch, the Contacts inside the switch may need cleaning, which can only be done by disamrling it or using a contact cleaner Like Deoxit. It will be hard to get inside unless one drills a small hole or soaks it. It helps to actuate the switch multiple times while the cleaner is inside.
If soaking I would do so in a closed container O/nite then set it in the sun or a warm environment to allow the solvents to evaporate before using it as i believe they are flammable.
It's possible the switch is worn beyond use. But I, again would inspect that terminal first

What is still puzzling is the car will run but the gauges etc. are flakey. Do they not both feed off IGN 1 ?
Also no V to the coil from Ign 2 in the start position but the starter relay engages? Are they also both not fed from the same terminal?

Those are definately possibilities.
I'd go with a trust but verify approach.
1. Remove the connector from the key switch. Check continuity from B to the other terminals with key in every position. Using resistance setting on the multimeter would be best.
2a. Check for continuityand wire colors between the connector cavity that matches I1 and the G1 wire terminal at the board.
2b Check for continuity and wire colors between the connector cavity that matches A and the G1 wire terminal at the board.


Once the wiring is sorted out, that shoudl take of the starting issue and hopefully also the gages.
But if the gages still have an issue, even though the other 'accessory' are working immediately, then its probably a connection on the board.
This is an instance where the voltage can read OK during testing, but doesn't reveal resistance. The resistance only shows up as a voltage loss whith sufficient current flowing through,
This can happen with the main feed as well, in particular with the 'MAD' approach. The battery is first in line from the alternator output. That could make the battery the path of least resistance back to the alternator's ground. If the distance and resistance to the rest of the circuits is long enough, high enough, then they don't get the full power until the battery is recharged.
I don't think that's what's happening here. The switch or its connections seem to be the culprit, or at least the main culprit.

Agreed on the continuity / resistance tests, but want to make the OP aware that one can show little to no resistance with a meter and NO LOAD on the circuit / dervice. But it may not be able to pass enough current through the switch /terminal/wire for the load, which would then cause a voltage drop due to the resistance.