Understanding ignition wiring on my 1970 Dart

[str12-340]

Help! I'm trying to understand why critical power for my ignition system goes through the printed circuit board on the back of my instrument cluster. Again this is a 1970 Dart with a standard cluster. I'm not talking about the ammeter gauge which I bypassed to an independent ammeter gauge under the dash long ago. I have been trying to chase an ignition based problem that can be resolved by pushing around the wiring under the dash. To help figure it out, I took out the seats, dropped the steering column and took the instrument panel loose so I could hook up the panel without it being in place. I discovered that with the car running, if I disconnected the 5 wire plug on the side of the instrument panel toward the center of the dash, the engine would die, plug it back in and the car starts fine, pull the plug and it dies. That seemed odd. What about the fuel gauge, temp gauge, oil light and dash lights (the only electrical items in the cluster) would cause power to the ignition to be lost????

Spending some time with my Chrysler service manual I found that the center wire on the three wire part of the Plug (as opposed to the two wire part), labelled G5-18dbl (18gauge dark blue wire) runs to a splice* and then wire J2A-16dbl goes to the bulkhead connector at position N. Go to the engine compartment diagram and and you see that wire then lead to something ominously labelled "NUMBER ONE SPLICE" with wires leading to the ballast resistor (J2A), the voltage regulator (I)(J2C), and one of the fields on the alternator (J2D). This is clearly seems to be why the ignition shuts off when you pull the plug... the question is what is the reason for this to go to the printed circuit board on the instrument panel. The one missing diagram in the manual is for the circuit board itself. Looking at the back of the circuit board it seems that this connects the oil pressure light to Bulkhead connector position K which leads only to the oil pressure sending unit screwed into the block.

*The other wires from the splice where G5 and J2A run to the brake warning light, to one of the wires in a connector leading to the ignition switch in the steering column and when traced goes to the gear selector indicator lamp, and to a key-in-ignition buzzer.

Is it really possible that this is wired so that if low oil pressure triggers the light that it shuts off the engine?!?!?!

Again HELP!!!

 

[67Dart273]

You are missing something, here. Let me see if I can chase this down

G5-18DBL is the switched power feed TO the oil pressure lamp. The lamp lights when the oil pressure switch grounds at low pressure.

The splice is merely a place to split off all the "ignition run" feeds to the various places to which they branch off and go

Your clue is "J2-16DBL" which comes FROM the ignition switch connector. This in effect is the "master wire" and the ignition switch is the SOURCE. The power goes from the switch TO the splice, and branches off from there

 

[67Dart273]

I think what you REALLY DID is that you have a loose connection somewhere and when you pulled that connector off, you also "jiggled" the loose connection a bit and thought that the dash connector is the problem.

I would do this:

Check where IGN1 / dark blue "ignition run" goes through the bulkhead and CHECK THAT TERMINAL for loose/ corrosion/ burned and wire connections.

Then run down that splice and see if IT failed.

What have you checked?

Another way is "when" the engine has just died, go to the "usual suspects" and check for voltage.....

Check at the ignition switch connector where the blue comes through, check BOTH sides of the connector halves. Check the engine side of the bulkhead connector and if that is dead, check where it goes through the interior side.

And check the splice itself

 

[67Dart273]

Your "functional current path" (this is wrong as this is from plus to ground instead of electron flow, is........

"Out of" the key on DBL, through the ignition switch connector on J2-16DBL

.........and to the splice

From the splice on J2A-16DBL and to the bulkhead connector position N

(Be wary of mistakes in the manual here)

...........To the engine bay diagram..........

From N of the bulkhead connector on J2-16DBL to the "number one splice"

From that splice on J2A-16DBL to the ballast resistor. Then this will vary depending on whether you have points/ or some other ignition. THAT POINT RIGHT THERE is the definitive ignition supply voltage

 

[67Dart273]

None of the other wiring matters unless it is shorting to ground, which should cause smoke and "meltage." Again, check at each point AND THE SPLICES for loss of power. "Wiggle test"

Your main places of failure are (in no order)

the ignition switch itself
the ignition switch column connector
the bulkhead connector
the two splices, rarely

 

[rustycowll69]

None of the other wiring matters unless it is shorting to ground, which should cause smoke and "meltage." Again, check at each point AND THE SPLICES for loss of power. "Wiggle test"

Your main places of failure are (in no order)

the ignition switch itself
the ignition switch column connector
the bulkhead connector
the two splices, rarely

nice job. couldn't have said it better. honestly, probably couldn't have said it at all, without a lot of research and head scratching, hahaha.

 

[str12-340]

67Dart273, thank you Thank you Thank you for taking the time to help me ferret this out! Understanding the flow of the electricity (direction) was a big help. I am really sure that pulling the plug kills the ignition (did it too many time for it just to be a coincidental jiggling of another piece), but moving down the line in your responses gave me some new things to investigate, partially based on what is relatively new on the car or has been recently refurbished (like the entire engine harness and all the bulkhead connectors) as opposed to all the wiring in the steering column including the ignition switch ( which only has 48 years and 200,000 mile plus on them)!

Again, thanks for your efforts, it could take a while to run down, but I'll send a PM when I finally find the culprit.