dual ballast resistor (1973 Monaco)

[Phil64]

Hello,
Yesterday I had a problem with my 1973 Monaco (440 ci). When I activate the starter, there's no ignition at all, as if the coil were disconnected. But when I release the ignition switch, a small explosion as if the engine was trying to start. A very brief explosion, then nothing. Every time I test, it's the same. I suspect the (dual) ballast resistors, but a test light comes on at each resistor terminal when I'm in the "ignition" position.
I'm troubleshooting as best I can by short-circuiting the two ballast resistors on the connectors; the car starts immediately ! And I was able to bring it home.

Today I'm doing more tests, the dual ballast is OK / (5.5 ohms / 1.8 ohms), so I reconnect the connectors and the car starts !!!! I therefore suspect a bad contact on one of the connector.
I measured almost 14V at the ballast output on the auxiliary resistor side (connected to the control unit) and 8.5V on the coil side.

My question is, are these ballasts essential? Yesterday, I drove 10 km with both ballasts short-circuited!

 

[Fury1969WI]

if you're still running the factory mopar ignition module then, yes, ballast resistance is required. It's my understanding that the full 12v is too much for stock mopar ignition systems. You will fry that module running full 12V for any extended period.

However, my guess is that your ignition module is starting to go out. When those start to die one thing i've experienced is they don't like to start when hot. Check all the wiring and connections in the schematic you posted and if nothing is obvious i would seriously considering having another ign moduel on-hand.

Good luck!

 

[Fury1969WI]

found this post - extremely comprehensive and interesting (thanks again to @Vaanth )

ballast resistor do you need it??

 

[Phil64]

if you're still running the factory mopar ignition module then, yes, ballast resistance is required. It's my understanding that the full 12v is too much for stock mopar ignition systems. You will fry that module running full 12V for any extended period.

Yes, I have the original Mopar ignition. But I find it strange to have almost 14V (= voltage when the engine is running) at the output of the 5 ohm resistor. There should be less if the module draws current. Here it is as if the ballast does not exist.

 

[Fury1969WI]

Yes, I have the original Mopar ignition. But I find it strange to have almost 14V (= voltage when the engine is running) at the output of the 5 ohm resistor. There should be less if the module draws current. Here it is as if the ballast does not exist.

View attachment 738661

I'm no expert or electrical engineer, but (a) at least it's not 15V and (b) I wonder what your voltage is across the battery.

 

[Phil64]

Now I know why I have battery voltage at the ballast output "auxiliary resistor" (5 ohms): there is no current because the ICM is a 4-pins !!! But the ICM connector is a 5-pins and there is a dual ballast, all this misled me because I hadn't disconnected the ICM to check.
Besides, I had already replaced it a few years ago and the previous one (which I kept because it was actually OK) was also a 4-pins...

 

[Clover]

Your problem is the pickup in the distributor- replace it.