Ballast Resistor vs. Resistor Wire - 67 250
 

What is the difference between a ballast resistor (ceramic block with two posts) and a resistor wire, and how do I know which I need? I read a bunch of threads and couldn't figure it out.

I do not see a ballast resistor on my firewall but I do have a cluster of wires emerging from a square black box right next to the choke cable.

I changed out the points, condensor, cap, rotor, and plugs, but no spark. Auto parts guy suggested replacing the resistor first and then the coil, but I don't seem to have a resistor. Could the resistor wire be bad, if in fact that's what I have?

Any advice appreciated!

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

You have a resistor wire. Check it with a voltmeter and see if it's still supplying voltage to your coil. The coil gets voltage through two sources. While the engine is cranking, coil voltage comes from the starter solenoid. When you let the key back to run, it comes through the resistance wire.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

What exactly is the voltage check and what range of values would indicate a functioning vs. a faulty resistor wire?

With the key in run position, what 2 points do I check voltage across?

So if the coil gets voltage from the starter solenoid with the key in "start", and I'm not getting spark with the key in "start", then the resistor wire could not be the problem....?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Key on run, red lead of volt meter to the + terminal on the coil, black lead of voltmeter to a ground. You should see somewhere above 6 volts or so.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Much appreciated - I will check that at lunchtime!

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

You bet.

If you do have power to the coil, take a test light and hook it to ground and then put the point on the negative terminal of the coil. Now crank the engine and see if the light flashes.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

>>Key on run, red lead of volt meter to the + terminal on the coil, black lead of voltmeter to a ground. You should see somewhere above 6 volts or so<<

That would only be true if the engine stopped at a point when the distributor points happened to be closed.
Not much of a test. The test light will give better info, but what are you actually testing for?

Is this a NO START problem? What is the problem that you are trying to diagnose?

There is no electrical difference between a " (ceramic block with two posts) and a resistor wire". Both should have a resistance of 1.8 Ohms for a six cyl chevy distributor.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Yes, this is a no start (no spark) problem.

I had it running one day and the next day, no start and no spark.

Points, condensor, cap, rotor, wires, and plugs are all new. Coil is old and I was going to throw in a new one but the auto parts guy suggested checking the resistor first.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Put an hei in it and eliminate the resistor wire and the jumper from the starter.
Plus a hotter spark, better idle etc etc..

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

I have 4.8 volts from the coil positive to ground with the key in "run".

The test light flashes from coil negative to ground with the key to "start".

Eventually will put in an HEI but just want it running for a little while first (so my son can drive it to Prom - way better than renting a limo).

Suggested next steps?

Thanks for the input!

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Have you checked to see if the rotor is turning? (I was unable once to get an engine to start that I had driven the day before and it ended up being a broken timing gear) How did you check for spark? Do the troubleshooting before buying any more parts. (With the quality of the parts today you may be adding a problem) Disconnect the power wire from the coil and measure the voltage to ground. As previously stated you should see 6-8 volts. If not I would check the voltage at the ignition switch. It should be 12 volts. If it is OK then it is probably the firewall connector. If no voltage or less than battery voltage the the switch is suspect number one.
If the voltage at the coil is good then pop the distributor cap and do a careful inspection. The points are just a grounding switch. If your gap is correct then look to see if the ground wire from the breaker plate is intact and securely connected at both ends. Is the wire from the coil good with no cuts or broken spots. If it all looks good disconnect the other wire on the coil and hook a multimeter to it and to ground. Then open and close the points manually. It you don't see a high and low reading on the meter try unhooking the condenser to see if it makes a difference. (You could have a shorted condenser). If the meter never shows conductivity then the points are not closing, the contacts are insulated some way, or maybe there is an open in the wiring. (Could be either the wire to the points or from the breaker plate) If the meter is always showing conductivity then the points are not opening, or the wire to the points is shorted to the case. If so disconnect it from the points and test again. If all this checks out then you may have a bad coil which is easiest to check by swapping a good one in.
I just saw your last post and your volts are pretty low I would concentrate on the power to the coil first. Check the volts at the ignition switch

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Yes, the rotor turns.

I replaced the other ignition parts recently, although prior to the current problem, so I assumed they didn't suddenly fail.

I'll check the ignition switch voltage. This would be 12V coming out of the switch with the key in "run", right?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Yes it should be 12 volts( within a 1/2 volt of whatever the battery voltage is).

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

OK, so now I'm really confused.

I pulled the + wire off the coil - with the switch to "run" I had 12+ volts. So I figured the ignition switch is OK and with the other symptoms, I swapped out the coil.

Now I turn the key and I get I very short burst of power and then nothing. And now the + wire to the coil shows extremely low voltage with the key in "run".

Bad ignition switch after all? Or something else?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

=Can't be the points or condensor, can it? I have super low voltage at the + wire to my coil when it's disconnected from the coil. Points and condensor aren't even in that circuit, are they?

Seems like it must be either the ignition wiring or the switch. So I can run a wire from the unfused spot on the panel to the + on the coil with a ceramic ballast inline to bypass my wiring harness?

Appreciate all the insight and knowledge of you all.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

At any moment the points are either open, closed or opening and closing (cranking/running) so you may get different readings.
If I recall, the points closing allows current to flow through the coil primary to ground. Opening collapses the electrical/magnetic field, inducing high voltage on the secondary side, causing spark.

The system was designed for 6V so when 12V came around, points got cooked so they introduced a resistance to limit current. Or so I've read... Note current is limited because on points open, you should read 12V at the coil side of the resistance wire. An open always reads source voltage.

I think I'd pull a plug ground it and check for spark.
You can also jump around the resistor wire w/ a not resistance wire temporarily.
I'd also measure battery voltage across the terminals. A charged battery is 12.6V or more. Load it by say turning on the likes for some seconds first. Less than 12.6V is a battery in need of a charge.
Finally, condensers (capacitors actually) are in there to reduce arcing and wear on the points. A bad condenser can cause weak/no spark because current flow isn't interrupted.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Yes you can by pass the factory wiring that way. You will need to put a switch in so you can shut the engine off and de-energize the coil when parked. Be sure you tape off or otherwise insulate and secure the factory wire to the coil so it won't short out.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

I had the same symptoms with my 74. I had pertronix and hei in this truck but I like to keep the points in a 6 cyl I found my resistor wire exposed and corroded in a few places. I replaced the resistor wire right from the bulkhead with a 14 or 12 I think and run to a ceramic resistor on the firewall. Also wired to the starter like stock. Definitely starts and idles way better. It was a Chrysler application and I want to say 1.6 or 1.8 ohm. It was 12$ compared to 6-12$ a foot for the resistor wire for 6 or 8 feet.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

>>I pulled the + wire off the coil - with the switch to "run" I had 12+ volts.<<
As you should. You should get this same voltage with the + wire connected, but only when the points happen to be "OPEN".

Earlier you said, >>I have 4.8 volts from the coil positive to ground with the key in "run".<< Obviously when you read the 4.8V, the points happened to be closed.


>>Now I turn the key and I get I very short burst of power and then nothing.<<

POWER??????

>>I have super low voltage at the + wire to my coil when it's disconnected from the coil.<<

What super low voltage? Earlier you said you had 12+ volts.


>>Can't be the points or condensor, can it? <<

You stand a better chance of having a BAD, NEW Chinese made condenser, than having a GOOD 30 year old condenser.

Did you check the dwell when you installed your new points and then check the timing afterward?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Things keep getting worse.

I thought the resistor wire was the problem so I bypassed it with a wire from the unfused ignition port to the coil +, with an inline ceramic resistor. Now I have only +1.2 volts at my unfused ignition port with the key in "run". Previously I had +12.

Where is the power going? My battery is brand new and reads +12.6. Is my ignition switch bad?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

OK, so if I have 12V on the red wire, then my ignition switch is bad.

If I have <12V on the red wire, I have a bad connection somewhere between the battery and the ignition switch - bad bulkhead connection, fault in the starter solenoid, etc.....?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Did you adjust the points gap when you installed them or just put them in and tightened down the screw? What gap setting did you use?

LockDoc

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Yep, I gapped the points to .019 and tightened them down. Double checked nothing moved in there when the troubles started, too.

Where is the best place to find enough exposed wire or connector to check the red and other ignition wires? Back of the ignition switch or somewhere else?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

-
Try hooking a wire from the positive post on the battery to the coil and see if the truck will start. (If it starts you will have to shut it down by unhooking the wire from the battery) If you don't have spark then, the problem is in the coil or distributor.

LockDoc

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

So the red wire into my ignition switch is +12 and all the others coming out of the switch are like +1.5 with the key in "run".

Replace ignition switch?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Great advise

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

I replaced the ignition switch and I still only get +1.0 V at my ignition unfused port, and nothing when I turn the key.

I tried what LockDoc suggested - ran a wire from the + battery post to the + post on the coil. Confirmed with the voltmeter I was getting +12 at the coil. Turned the key to run and got dash lights (good sign). Turned it to run and the starter kicked for half a second and then nothing. Could not get it to even do that again on subsequent tries.

The coil, condensor, and points are all new. I'm about to pull out the new condensor and put the old one back in for the heck of it.

Any ideas?

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

ingnition switch would be my next guess

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

I put a new ignition switch in this evening and still had +1 V coming out of the ignition switch in "run" and +1V at my ignition unfused tabs.

And I also swapped out the new condensor and coil for the old ones and the symptoms did not change.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Yes - I have 12V on the red wire at the ignition switch

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Are you measuring that with the key on or off?

The reason I ask is because there could be a poor connection (excessive resistance) somewhere in that red wire between the battery and the ignition switch and it will only show up as a voltage drop when under load.

For example, with the key off and no current flowing through the wire, there won't be any voltage drop so you would read 12V on your meter. But when you turn the key to the on (or start) position, the ignition (and starter solenoid) draw current. And if that current is trying to flow through a poor connection it will result in an excessive voltage drop.

So if you were measuring 12V on the red wire with the key off, try measuring it again with the key in the on or start position. If the voltage on the red wire drops way down, follow that red wire back to the battery, checking for bad connections along the way.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

I think you have a bad connector in back of the ign. switch. These are nortorious for burning at the red feed wire connection. A replacement pigtail is available at parts stores.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Remove both battery cables and clean them good. (both ends). If it is an automatic make sure it is all the way into park (or try it in neutral). Make sure that the ground straps from the back of the engine to the firewall are there and connected. If there are no ground straps there install one from somewhere on the engine to the firewall.

LockDoc

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Got it figured out - kudos to all of you guys for helping me learn about my truck's ignition system, and especially LockDoc and ray_mcavoy for helping me think simple when things seemed most complex.

ray_mcavoy made a great observation that I had only checked for +12V at my red ignition wire with the key off. With the key in "run", voltage dropped to +1. Thus, I needed to find the source of voltage drop between battery and ignition.

I recently put a new battery in this truck, so I started with the battery connections. Fusible link looked suspect (couple frayed wires - maybe that's the source of the voltage drop - might have broken when I took the + cable off?). So I replaced that with a piece of straight 12ga wire, but it still wouldn't crank. Then I noticed the negative terminal on the battery was a little loose, so I took off the cable, cleaned both ends and the engine block, hooked it back up real tight and boom - away she went firing on all cylinders!

Lesson learned to always think simple and check your work - great teaching point for my son who wants to drive this truck to prom this weekend.

Thanks to all those who chimed in and helped me learn about this truck's ignition system. Although I replaced a lot of parts I didn't need to, they were cheap and it's money well spent to get my hands dirty on a truck I love. On to the next challenge - brake pedal that goes to the floor!

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

Good deal!! Glad you got it going. There is always another challenge...:)

LockDoc

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

The lesson that needed to be learned, is that there is a difference between the starter circuit and the Ignition circuit.

The title of this thread is " Ballast Resistor vs. Resistor Wire ". That alone implies an ignition problem and in your post #3 >>and I'm not getting spark with the key in "start", <<
You can not trouble shoot an ignition problem if the engine is not cranking over.




In your post #14 on Apr 20
>>Now I turn the key and I get I very short burst of power and then nothing.<<

I ask in post #24
POWER??????

If the answer to that was, the engine would not crank over, you could have had it running a week ago.
Efficient trouble shooting requires good information.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

I'm sorry to confuse, but that's what I had when I started the thread - an engine that cranked over but would not spark. I realize it morphed into something different, and likely I solved the spark problem while simultaneously creating a problem in the starter circuit.

I considered starting a new thread but wasn't sure if that was preferable to keeping all the information in one place.

Anyway, thanks to all those who weighed in.

Re: Ballast Resistor vs. Resistor Wire - 67 250
 

After forty years of repairing motorcycles, cars, trucks, tractors, tugboats, and ships, the number one rule of thumb I have is "ALWAYS look at the last thing you messed with". Glad to hear you got it solved.