What's the resistance supposed to be on a stock points ballast resistor?

[bull]

I'm restoring a ballast resisitor and am hoping to use the coil/connectors from a two speed wiper resistor but I need a resistance value to see if it's a match. Thanks.

[Dans 68]

My "original looking" ballast resistor reads about 2.3 ohms with no current load on it. Now I believe that the resistance tends to increase or decrease directly proportional to the current flowing through it, so it may be difficult to mimic the original parts operation. 

Dan

[bull]

Thanks. Are you running a points ignition?

[greenpigs]

I have checked and the parts store has the 1 Ohm listed for the replacement, but I think the service manual shows a .8 Ohms resister which MSD makes but doesn't look like the original. The reason I was looking around too find a low resistance replacement that will give a little more juice to the coil or so I have been told.

[bull]

I have checked and the parts store has the 1 Ohm listed for the replacement, but I think the service manual shows a .8 Ohms resister which MSD makes but doesn't look like the original. The reason I was looking around too find a low resistance replacement that will give a little more juice to the coil or so I have been told.

I need to look into that too because I don't know what resistance I'm supposed to be running either. And as of yet I'm not sure what type of ignition system I'll have. Initially I was going to run MSD, and then I switched to Street Fire (MSD light) and now I'm waiting around for this Rev-n-nator thing to get going: http://www.thertgarage.com/products.html

[Nacho-RT74]

as far I remember it is like this:

1.5 on points

1 to 1.5 on ECU

performance, from 1/4 to 1

[bull]

as far I remember it is like this:

1.5 on points

1 to 1.5 on ECU

performance, from 1/4 to 1

So what's with Dan-o and his 2.3 business up there?

[Dans 68]

Tolerances and loosely sticking the multimeter probes in the ballast resistor tabs (increases resistance).

Dan

[bull]

Well, I just dug my original (I think) ballast resistor out and it reads 3.2 ohms. But it's covered in overspray and full of dirt and junk. Not a good mark by which to judge a restored one I'm sure.

[greenpigs]

Tolerances and loosely sticking the multimeter probes in the ballast resistor tabs (increases resistance).

Dan

X2

  Plus it depends on what your coil can handle. I use a MSD blaster 2 hi vibration & it only needs .8 OHMs IF running points otherwise you do not need to run one. Of course keeping the MOPAR ECU requires running one but the .25 OHMS resistor would work. I decided to play it safe and go with the MSD .8 but my flippen Holley fouled my plugs yet again so I don't have any results if it starts\runs better.
FWIW I am going to run my Eldelbrock 750 again till I sort the carb out & check to see if the power valve is stuck open like Ron suggested.

[oestermarken]

The one in my '69 is the 0.8 ohm type. I'm almost sure it's the original one

/Brian

[terrible one]

I think Dans 68 nailed it. The operating resistance (when the ballast resistor is hot) is lower than the cold resistance. For example, I have the MSD 0.8ohm resistor and it measures at 2.1 ohms. The "stock" electronic resistor it replaced is marked 1.2 ohms and reads 2.4 ohms cold. Dans 68 likely has a 0.8 or 1.0 ohm resistor.  

For what it's worth to those of you with "mystery" resistors, the resistance is often stamped onto one of the terminals if you look closely.

[Nacho-RT74]

just checked at the haynes manual... I have to correct:
single, breaker point: 0.5~0.6 ohms
single, electronic:  1.12~1.38 ohms
Dual, Primary, Thermal:  0.5~0.6 ohms
Dual, Primary, NON Thermal:  1.12~1.38 ohms
Dual, Secondary: 4.75~5.75 ohms

[terrible one]

just checked at the haynes manual... I have to correct:
single, breaker point: 0.5~0.6 ohms
single, electronic:  1.12~1.38 ohms
Dual, Primary, Thermal:  0.5~0.6 ohms
Dual, Primary, NON Thermal:  1.12~1.38 ohms
Dual, Secondary: 4.75~5.75 ohms


~~~~~~~~~~

INCORRECT... THE HOTTER THE HIGHER... GAS NEED LEES SPARK TO BURN WHEN HOT.

If was opposite, we wouldn't get a bypass circuit to start up the engine being cold.

Fair enough. So why do some resistors read higher then?

EDIT: Using aligator clips instead of the probes I was able to get the rated reading from my resistors. 0.8 for the MSD and 1.1 for the 1.2 ohm one I have. The mystery continues I guess lol 

[Nacho-RT74]

I edited the post before your reply... I'm not completelly sure about hotter the engine higher the resistence due gas requires less voltage to burn, recently read the ballast changes the output as far is heated by voltage going through with RPMs, increasing voltage with more RPMs