Technical Chevy ignition question, ballast resistor or not

Im working on a friends Chevy C20. I did a transmission swap. When I went to start it, it was running really rough. It wouldn't stay running unless I kept my foot on the gas. I put in a carburetor kit, flushed the gas line, and swapped the tank. There was a lot of rust in the tank and carb. Its running two filters now, one after the tank, and one before the carb. There IS clean gas getting to the carb now.

After that, I noticed it was getting a weak spark when I disconnected the coil wire at the coil. The coil was also leaking oil. It does not have a ballast resister now. My buddy said it was running smoothly when he last started it last summer.

I picked up a new coil and it says "USE WITH PRIMARY RESISTANCE WIRE OR EXTERNAL RESISTOR". I'm assuming they mean a ballast resistor. I have looked up wiring diagrams online, and haven't seen any with a ballast resistor on the diagram. I don't know if it has a "primary resistance wire". It has some wires that are melted, and a new wire harness is in the plans ahead.

I would like to know if anyone else is running a ballast resistor and how you wired it? Also, how do I know if it needs one? What should I look for?

Thanks in advance.
Art

 

If you got a points dizzy. Originally off the starter outside small "R" terminal was a resistance wire often fuzzy coated. Since we are not sure of its shape & if you don't want to ohm it you can go to Parts store & have them get a Borg Warner RU-12 or better yet RU4 resistor "its gm based " & wire it in between the "R" terminal & the coil + terminal. Once again various ways to do this but one of the easiest. Flux

 

Thanks, Flux. The wire from the starter to the coil now, is one that I made. The previous one had chips and cracks on the insulation plastic around the wire. And it is coming from the "R" on the starter. Is a Borg Warner RU-12 resistor available at an autozone? All the good parts stores near me have disappeared.

 

what year truck is it? Starting in the early 60s, thru 1974, chevys used a (usually braided looking insulation) resistance wire from the ignition switch to the coil+, and a yellow bypass wire from the starter R terminal to the coil +.

 

They'll have something it'll cross to just have Em interchange that number sir. I work in a non-box store myself. Since birth! Flux

 

Yes indeed, our one owner 69 C10 original harness is just using the starter supplied resistance wire. It may not be the typical setup being a manual 3 speed overdrive, the overdrive silinoid harness ties into the ignition harness so our passing gear will apply. It could be an exception. But on other hand our 72 Monte carlo has the Ign switch suppling it "fuzzy" braided wire along with the yellow "R" wire Running up from the "R" on the starter. There I'm sure is reasoning to gm's different resistance sources. Thanks , Flux

 

Sorry, 1963 c20, 283 v8, 2wd.

 

There wasn't any braided wire or anything different about the wires it had previously. Nothing looked out of the ordinary. I'm a Mopar/Ford guy. It's the first Chevy I work on. So, I wouldn't know what to look for.
If it didn't have a resistor wire before, would it even run without burning the points?

 

It'd run but would eventually burn them unless it had a internal resistance coil swapped on it like an older ford vehicle had. Not quite 1.82 ohms resistance like the RU4 resistor but they'll do in a pinch.

 

The coil you have says to run a resistor. Test voltage at wire from ignition to coil +. If you have 9 or so, it may be resistance wire. (If battery has 12+) If 12 at coil, mount resistor on firewall (they get hot), run wire from IGN to input side, check output side voltage. If 9 or so, connect wire to coil +.
The ballast bypass wire from starter connects to coil+ and should supply full battery voltage to coil ONLY during cranking.
Make sure coil- goes to distributor and coil+ comes from resistor and bypass.

 

Check the voltage at the coil, my '64 c10 has a resistance wire.

 

@ rfraze, so if I have 12v at the coil, you're saying run 2 wires to coil +. One from IGN, to br, to coil+, and one from starter to coil +?

 

That's correct. Make sense? That coil and points are set up to run at a lower voltage than 12. Test voltage at coil+ while running or w/IGN on. Should run at voltage coming out of resistor.
The bypass wire comes from the other small terminal on solenoid (not the trigger wire from switch). Someone above called it the R terminal, which means that it could be hooked up on output side of resistor or on coil+. Whichever looks better, right?
Just make sure that wire from starter is only hot while cranking and gets its power from inside the solenoid, not the key. One small pole on solenoid triggers solenoid and starter. The other one does not, but gets full battery voltage, while solenoid is engaged, providing extra voltage temporarily to coil during starting. You can test bypass wire voltage before connecting it to resistor output or coil+, to see how much voltage is coming thru starter. Should be near battery voltage during cranking only, then back to 0.

 

What rfaze says, the coil burnt due to lack of a resistor in the ignition switch run mode, be it wire or external, you can buy the wire but the external will be easier to find, crank mode 12V, run mode 9V or abouts

 

Take the information from Rfraze.He helped me on my wiring problems.Bruce.

 

When you are measuring the voltage at the coil, make sure the points are closed. If the points are open, you'll probably see 12v with or without the resistor. Something about Ohm's law, voltage divider circuits, etc.

 

Guess what I should have said is, if you have 12 volts at the end of the disconnected wire to coil +, and you have a coil which needs resisted voltage, install a ballast resistor between IGN switch and coil+. Then test the wire again before connecting to coil.

Bruce had a LOT of people trying to help him.

 

Yes I did and thanks you all.Bruce.

 

I wish I could say I have already resolved this issue, but I'm surrounded by f#@$ing idiots.
I will have to find an other parts store close to my work, cause Napa by my house closes before I get home. These dumb asses don't have a clue, unless it's on the screen in front of them. And then, they try to act like they're master mechanics. It's hilarious.

 

Picked up a 1.2Ω ballast resistor at Napa today. I hope it does the trick. Finally talked to a parts guy that could tell me about the part he was selling me.

The jackass at AZ told me "they don't even use those anymore".

 

Test voltage out of resistor before hooking to coil+.

 

I was not going to get into this one, but squirrel has it right. Without current flow through the resistor there will be NO voltage change across it. The points need to be closed. Connect the coil.

 

Woops. So, current thru the volt meter to ground is not enough to get a proper reading?

 

GM started using primary resistance wire in '64 before that they used a ballast resister. With your battery hot take your volt meter and see what voltage you are getting at the end of the primary ignition wire (the one that goes from the switch to the coil). if it is 12v + you need a ballast resister and if it is 9V- you do not.

There will be a wire then runs from your starter solenoid to the + side of the coil it will be 12V when it is in start mode. But it will not be hot when the engine is running.

If the coil was leaking you did well to change it, you should also check the points. make sure that they are not burnt (they should have a smooth shiny face), if the face is smooth but they are dirty take a dollar bill and close the points on it then rub it back and forth that will clean the points well enough to use. If you don't have a dwell meter set your points with a feeler gauge @ .019 if you don't have a feeler gauge or a dwell meter use a match book cover it will get you close enough to run until you get the proper tool.

OK?

 

A voltmeter is an infinite impedance. It presents no load to a circuit, draws no current.

 

Current through the volt meter is fine you are only checking supply not draw. its not a TV set its a damned old chevy.

You need load to check amperage not voltage supplied.

 

Thanks for the input.
Maybe RnRDaddy could give us a real world test disconnected and connected (w/points closed)
I will open this discussion over on How to use a volt meter thread.
http://www.jalopyjournal.com/forum/threads/how-to-use-a-multi-meter-volt-meter.960762/

 

Its a good test if you are checking amp draw or resistance, it is useless for testing supply voltage or line if you prefer which is what he needs to test to see if he needs a resistor or not. You supply is what you have prior to usage that is what determines if you need to ad a resistor or not.

All this is well and good if you are testing electronics or if you want to get into ordinance (demolition) school in the navy or a navy based branch of the military. It is basically overkill when you are trying to see why your car won't run when there are way simpler methods. The reason that many people are afraid of working on their cars is that a precious few make it so damned complicated when it doesn't need to be complicated at all.

 

Beaner, The OP already did this and determined that he needs a resistor. He had trouble finding one and listed the one he found as a 1.something ohm resistor after a previous poster mentioned part numbers and a much higher resistance. Wouldn't doing a simple, I thought, test for voltage out of resistor let him know if it IS the right resistor?

 

After he bought it, it would. or he could have just gone to the 'Zone or any other parts counter and asked for a resistor for a '64 Chebby. They are still in the computer I buy them all the time as well as those for Ford and Mopar.