ballast resistor resistance?

[kittypancake]

How many ohms resistance should a ballast resistor read? The one in the car has 12v on both sides, so I'm guessing thats not right. The used one I have sitting around reads 0 ohms resistance, so I'm guessing tha's not right either.
Am I checking these thing correctly?

 

[70aarcuda]

never mine

 

[Bad Sport]

They vary, 1.5 to 2.5, I think. Maybe a little higher. Don't quote me on it LOL.

 

[67Dart273]

1-1.2. Not over 1.5 Most meters are not accurate the lower the resistance gets.

Short your probes together and see what the meter reads

You cannot "short" a ballast to less than it was originally built. If your meter checks it at zero, it's good. This is because they are a wire wound resistance. There is simply no way that they can FAIL with substantially less resistance than they were manufactured with.

Usually, a ballast either fails "open" or "intermittent," IE it's broken inside and makes contact some of the time

 

[kittypancake]

1-1.2. Not over 1.5 Most meters are not accurate the lower the resistance gets.

Short your probes together and see what the meter reads

You cannot "short" a ballast to less than it was originally built. If your meter checks it at zero, it's good. This is because they are a wire wound resistance. There is simply no way that they can FAIL with substantially less resistance than they were manufactured with.

Usually, a ballast either fails "open" or "intermittent," IE it's broken inside and makes contact some of the time

OK then...guess I gotta look somewhere else

 

[67Dart273]

Make sure it's reading what you think. Meters "vary." What does the ohmeter say with the probes disconnected? This is the "infinity" reading. Short the probes and see what it says. Digi meters rarely read "zero" with the probes shorted.

My Flukes, example, say 0L at infinity, which is supposed to mean "OverLoad" a stupid and counterintuitive reading for "infinity." This could easily be mistaken for ".o1" ohms.

 

[ir3333]

cold,in and around 1 is fine and as stated, at that lo a resistance your meter will be out .3 or so.
when operating, the resistance changes with heat... i.e."ballast"
and yes it should be for 12v (12 volts)
this just limits the voltage to the coil to 8 or 9 volts,and some argue you don't need one for electronic ignition.

 

[67Dart273]

OK then...guess I gotta look somewhere else

Maybe you should ask the REAL question?

I assume you have an ignition problem?

Any spark at all? What have you checked? And what year/ model, and what is the ignition system?

 

[BillGrissom]

The main thing is the voltage at coil+ (red lead) with the black lead on BATT-. You should read ~8 VDC (average) with the engine running, if points or the OEM Mopar box. If lower, you have excessive drops in the connectors, key switch, or ballast.

When you measured 12 V on both sides of the ballast was the engine running? If not, you did a bad thing - you left the ignition in "run" with the engine off. I have read that can burn-up your points or Mopar box (black epoxy runs down the inner fender).

 

[kittypancake]

Maybe you should ask the REAL question?

I assume you have an ignition problem?

Any spark at all? What have you checked? And what year/ model, and what is the ignition system?

no spark at all, I'm trying to figure out why and I had no idea how to check a ballast resistor. Car is a 72 Valiant with slant 6 and has a Pertronix ignitor. I'll go try to chase what's wrong down when the new batch of snow melts...ENOUGH ALREADY!

 

[wjajr]

Ballast resistor is just a resistance coil no different than a light bulb filament, or stove burner. It will conduct electricity if good, and won’t if bad, in other words if the resistance coil is still whole not broken it will work to step down voltage. If it is open, or rather its coiled wire has broken into two disconnected lengths of wire, it won’t conduct electricity just as a burnt out light bulb filament opens the circuit.

The way it should work:
Mopar ignition design utilizes two current paths; start and run. When ignition key is in start position turning over engine, start circuit bypasses ballast resistor providing coil with 12v for easer starting. Once engine catches, and key is released flipping back to run, power is diverted through ballast resistor to step down voltage to a coil friendly 5 to 8 volts depending on its resistance value.

When ballast resistor fails the engine will start and run as long as key is in start position bypassing ballast, and once key moves to run, engine dies. Occasionally ballast resistor will selfheal like a light bulb sometimes dose by self-welding filament back together only to soon fail once again; this almost never happens.

I suspect that the problem you are experiencing is rooted in Pertronix device, or ignition wiring. Not having seen a Pertronix set-up I can’t help with that device, but carful testing of ignition circuits will expose bad wiring, switches and or connections that serve coil and distributor.

 

[67Dart273]

Pertronix. Simple. Jumper 12V to wherever the Pertronix is hooked, and make sure the coil is getting power, IE temporarily bypass the resistor. IF you get no spark, it's either the coil or the Pertronix, so whatever is cheaper or lying around is what you replace.

The destructions:

[ame]http://www.pertronix.com/support/manuals/pdf/ignitor12vneg.pdf[/ame]

Your wiring should look like this, from page 2 of the manual. You should also have an additional wire coming from the original harness (brown) hooking to the coil + side of the ballast resistor.

Also, it's important to understand how a Mopar ignition switch/ starting / running circuit works.

1--You have "IGN 1" or "ignition run", traditionally blue, which is hot ONLY in run. This wire is what provides power to ignition for running, but is NOT hot during "start."

2--The bypass circuit, or "IGN 2", which is a separate set of switch contacts in the can which is the "ignition switch." Traditionally brown, this wire goes from the switch, through the bulkhead, and to the coil + side of the ballast. It is the ONLY source of ignition voltage during cranking.

 

[kittypancake]

HEY! Thanks for the link to the instructions! I dug around and found another coil. Maybe soon I can try this again...wish I could carve out more than 10 minutes at a time to work on it. Gotta check the weather forecast for Friday.