Ballast resistor wiring

[Righty]

I'm wondering wether I should replace my ballast resisitor, quite often the engine will fire when cranking and then die when the key is released or just drop away and die when reverse or drive is selected, idle is quite fast probably too fast. Up front I know nothing about this at all I'm just trying to pick up from what i read on FABO and a failing ballast resistor is perhaps one of the causes for this type of behaviour.
I thought it would do no harm to replace it as a process of elimination or at least keep a spare to hand.
The first issue I'm having is the only 4 pin resistor i can find is the RU12 which has a resistance of 1.4 cold and 5 operating which seems at the cold end of the range quite high compared to some of the recommended ranges that other members have shown from the manuals.
The other thing i have found is that the previous owner has a slightly non standard wiring of the resistor as shown in the photo. I have labelled what i think the wiring should be according to the diagram from the manual, but there appears to be an additional wire on the ignition connection. I would like to make all these connections a bit more robust but I'm not sure as to what is going on here.

 

[halifaxhops]

Sounds like a issue with the run circuit. I would look for a loose splice or connector terminal the way you describe it around the colum since it is dropping off when put in gear sometimes.

 

[Mike69cuda]

If you take the connector off your ECM, does it have 4 pins or 5? If it only has 4 pins, the 5 ohm side is not used and wiring to it is not necessary.

The replacement ballast resistor value is fine.

Dying when you release the key is likely two main causes:

1. Bad ballast resistor.
2. Bad ignition switch.

Could also be loose connections on ignition switch, ballast resistor, or bulkhead connector.

What year / model are you working on? That would help identify wires.

 

[Righty]

So I'm asking dumb questions here but the run circuit is that from the alternator to positive on the coil (labeled above on the drawing as ignition cranking)? What role does the ballast resistor play in that? I can see that it would control the voltage from the battery when starting, but it doesnt look like it is part of the run circuit. Sorry I'm probably talking gibberish. I think I should probably go and buy a book on this.

 

[halifaxhops]

It drops the volage so the coil does not cook. I still have a few books left if needed.

[SOLD] - electronic ign Trouble shooting book

I have some copies of a great book for trouble shooting Mopar electronic ignition with a ohm meter. Askin $28shipped lower 48 Shoot me your e mail I will send a paypal invoice. This will trouble shoot the system not bench check a component

www.forabodiesonly.com

 

[Righty]

OK so its a 69 Barracuda 318, so I am assuming the ECM has been added later in place of points ignition. The ECM has 5 wires out so I have assumed its a 5 pin.

 

[halifaxhops]

Your really going to love this if it is a Mopar ecu and has 5 pins yes dual ballast. Now aftermarket can have 5 pins and is really a 4 pin.

 

[Righty]

I'm in the UK so a bit far to borrow your books, but I would take a recommendation with gratitude and see if I could find it here, I'm a practical bloke when it comes to making and building, but my mechanical and electrical knowledge is pretty much base level. But my goal is to change that.

 

[halifaxhops]

Where is that ecu mounted? Also what is the two pin ballast under it? Looks like the origional for the points.

 

[Righty]

I reckon its OEM

 

[halifaxhops]

I'm in the UK so a bit far to borrow your books, but I would take a recommendation with gratitude and see if I could find it here, I'm a practical bloke when it comes to making and building, but my mechanical and electrical knowledge is pretty much base level. But my goal is to change that.

I put them together a few years ago and sell them for the printing cost and the ride.

 

[Righty]

Looking at it from the front the ECM is top right on the firewall and yeah that does look like it could be the original ballast below.

 

[halifaxhops]

Yes thats factory so it is a 5 pin. One thing that has to have a really good ground to the firewall where it is bolted to.

 

[halifaxhops]

Looking at it from the front the ECM is top right on the firewall and yeah that does look like it could be the original ballast below.

LOL I need coffee thought is was the upper fender for a minute!

 

[halifaxhops]

So it just shuts off when you move the shift selector right? Is any of the linkage rubbing anywhere?

 

[Righty]

The changes that have been made coupled with my severley limited knowledge is giving me inertia when it comes to tackling jobs like this! So like the additional wire to the ballast because it doent tally with the diagrams I have seen I would be clueless as to its purpose.

 

[halifaxhops]

I think when it was installed they pulled the "new" power to the coil from the old ballast resistor. Whats weird should have been the plug with the two wires one should be run the other crank. Do you have a factory service manual for the car? Also is it a USA car or a export? Not sure if they are wired the same.

Great people here we will get you through this.

 

[Righty]

It tends to be on starting it will idle and then when the shifter is moved to reverse it will shut off, if i persist and get it idling for a minute or so it will usually settle, the linkage seems fine, although it has a quirk that it will only engage park after engaging reverse and then pushing through neutral to park. Going from drive or Neutral to park it tends to roll or reverse! I wondered if it could be the neutral safety switch playing a part, so possibly affecting the shift lever movement, but also wether it is part of the starting issue.
The 4 pin ballast is on the upper fender.

 

[halifaxhops]

The NSS is really only for the starter, If it was bad you would not crank. Have to ask this you know for sure you are loosing the spark? Just asking because of the high idle.

 

[Righty]

Yes that is what I thought from looking at diagrams is one should be run the other crank but their all on the battery side. Its a US built car, butwas built as a RHD export to the UK, so it has a Valiant dash. I think/ hope that initially I can look at replacing the resistor with a new one, and at that point I will copy the wiring set up as it is but just put better terminals together. I think in the longer run, I need to strip some of the cable wraps away and start tracing where these circuits go and try to draw up a schematic, without that I'm just chucking out half questions but maybe with a clearer picture some of you FABO guys might see whats going on.

 

[halifaxhops]

Just check the ballast resistor with a ohm meter. Usually when they go they blow like a fuse. So you have OEM wiring diagrams? That and what is posted here is a add on to the factory wiring.

 

[halifaxhops]

Mike any Ideas?

 

[Righty]

No I couldnt say for sure that I'm losing the spark, it was more a thought that the intermittent issue of shutting off after releasing the key might be an indicator of an issue with the ballast resistor or its connections. Because it is an intermittent problem I thought swapping out the resistor and tidying the connections would eliminate a possible cause.

 

[Righty]

I have oem diagrams for the model year from MyMopar, but they are points based and then I have tried to find information on how the ECM is typically wired up. You know what they say, " A little bit of knowledge is a dangerous thing" that's pretty much nail on the head for me right now

 

[halifaxhops]

Thats where I would start also. Make sure that ECU has a good ground also. Then if it is the same you have to make sure you are loosing spark. That idle and then dropping it in gear can make it stall also.