Why the second resistor??

[charliec]

Working on my '68 Dart, 340.
The first photo is from the Illustration Section of the 1968 Parts Catalog. It shows a single ballast resistor in the system.
The other photos are from years ago as I was dismantling the car. They show two resistors in the system, and I don't know what the second one is for. I think that the upper one is the ballast resistor for the alternator. What is the other one for?

 

[HemiSSDart]

Because someone added Mopar electronic ignition and it comes in the kit so he decided it needed to be in the system, it is not needed...

 

[413]

We have no idea how the person wired your car so it may not start or run if you remove one.

If they wired it to the instructions for a 4 pin box it only needs one ballast resistor.

 

[Professor Fate]

Here's a thought-
If a 5 pin ECU was wired in, PO might have figured that since a 4 pin ballast was needed, he'd just add a second 2 pin ballast to the system and call it good...? You'd have to chase some wires to find out.
Stranger things have happened.

 

[RustyRatRod]

You'll need to trace the wires to confirm where they go.

 

[67Dart273]

Here's a thought-
If a 5 pin ECU was wired in, PO might have figured that since a 4 pin ballast was needed, he'd just add a second 2 pin ballast to the system and call it good...? You'd have to chase some wires to find out.
Stranger things have happened.

This sounds most probable, and to add, that resistor would be the wrong value, because both halves of a 4 pin are different values.

OP the one resistor for an electronic wires up just like it had points. In fact if the ECU ever dies, and you happen to have a breaker points dist, you can just unplug the ECU, connect the points dist. to the coil NEG wire, and plug it into the engine and time it

 

[Mattax]

I think that the upper one is the ballast resistor for the alternator.

Misunderstanding the 'ignition' circuit and the alternator 'field'.

The 'ignition' circuit feeds both the ignition and the alternator field.
The branch going to the ignition runs through a ballast resistor.
The branch going to the alternator field goes to the voltage regulator.

For 1967 and 68 the branch going to the alternator begins at the connector to ballast resistor.

I suspect the second resistor was used because it came in the kit and whomever installed the kit assumed it was different than the points resistor.

Here's how an newer ECU gets wired in.

We can see one wire on the new ballast is blue and yellow. Typically that was the color for the power feed into the ECU. If thats true, then the other side somehow was spliced into the original ignition.

Honestly I don't love that location above the seam. Below in the factory location seems to be better protected from water.

 

[67Dart273]

LOL the WEIRD thing is that we have ANOTHER thread with a mystery second ballast, and that one indeed seems to be (wrongly) wired into the VR!!

 

[Mattax]

and that one indeed seems to be (wrongly) wired

I think that sums up that other thread!

my answer there is now

 

[413]

This is his car, it is an orange box, it has 4 pins.