Checking an Ignition Ballast Resistor

Jeff/Illinois

Jeff/Illinois

Well-known member
I did a search and didn't really fine what I was looking for.

My question is, what should the Ohm reading be on a good ballast resistor and what would it be on a faulty one. Rheostat looking resistor under the dash, '36 Ford with a '46 59AB flathead.

One last question. Where do you buy a GOOD dist. condenser for a crab style distributor also a '46 59AB engine.

Thanks much.
 
Need some missing information here.

Original style coil or newer "can" style?

6 volt or 12 volt system?

What does the under the dash ballast resistor look like?

An original would look something like this:
 

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Resistor is .5 ohms, that's half an ohm approx. A bad resistor would be a higher reading or no reading at all. Only use an original FORD made resistor as modern reproductions have been known to have issues. Regards, Kevin.
 
Thanks for the help here.

I forgot to mention, 6V original system with a 'modern' can type coil. The coil is maybe 5 years old it is a Standard brand part.

The under the dash resistor looks like the one pictured with a 20 amp Buss fuze attached beside it.

I will try to get out to the garage in a couple of days and let you know what I find. I will re-check that resistor it LOOKS OK not burnt or anything like that but I'll hit it with my tester

Thanks again
Jeff
 
meric42 said:
The best 'off the shelf' condenser Napa FA54, doesn't look the same as original but reliable.

https://www.fordbarn.com/forum/showthread.php?t=276949&highlight=FA54
Click to expand...

Thanks for this info, my condenser looks a lot like this one but I noticed that the wire lead is frayed and the insulation looks like it is toast. Never noticed that until I started running down the electrical gremlin.

I have plenty of fuel, fuel pump working fine accelerator pump squirts to beat the band. No spark at the plugs so I'm going that direction.

I'll let you fellows know what I find. Thanks again.

P.S. I was a Ford Parts Manager at the local Ford dealer back in the early 70's, and not a mechanic! I know the parts and what they do so that helps!

Jim Linder at Bubba's Ignition rebuilt my dissie about 7-8 years ago and did a fantastic job. I see he uses the NAPA FA54 condensor so I will call down to our local NAPA store and get one ordered
 
A can type coil indicates a conversion from coil on helmet remounted to can somewhere else. The can type coil conversion adapters for the helmet distributor can be problematic. If you are useing a can type (modern) coil with a 1.5 ohm primary winding and running the car on 6-volts, you won't need a ballast resistor.

If you deside to find a good core coil to fit your 1936 Helmet distributor, you can get Skip Haney to rebuild it for you. It will work better than new but you would need the original type ballast resistor with it.

http://www.fordcollector.com/coils.htm
 
The ballast resistor needs to be by-passed with the modern coil. This is easy to do by moving the wire from the ignition switch to the resistor. At the resistor end remove the wire and reconnect it to the side of the resistor that has the wire going to the coil. All done. Also, be sure the ignition wire to the coil connects to the (-) terminal on the coil and the (+) terminal connects to the distributor/capacitor/points. On some coils the (-) terminal might be labeled Dist and the (+) terminal might be labeled Bat.
 
JSeery said:
The ballast resistor needs to be by-passed with the modern coil. This is easy to do by moving the wire from the ignition switch to the resistor. At the resistor end remove the wire and reconnect it to the side of the resistor that has the wire going to the coil. All done. Also, be sure the ignition wire to the coil connects to the (-) terminal on the coil and the (+) terminal connects to the distributor/capacitor/points. On some coils the (-) terminal might be labeled Dist and the (+) terminal might be labeled Bat.
Click to expand...

Got it thanks did not know this.

I'm a 'Model A ' guy by trade flatheads are 'new' territory for me:o I can trouble shoot a Model A Ford easier than these dogs.
 
You need to check the primary resistance of the coil to know whether you need a resistor or not. You want a total of 1.5 ohms.
 
flatjack9 said:
You need to check the primary resistance of the coil to know whether you need a resistor or not. You want a total of 1.5 ohms.
Click to expand...

True, but was assuming it was a standard 1.5 ohm 6v coil. As flatjack posted, it is always best to check.
 
koates said:
Resistor is .5 ohms, that's half an ohm approx. A bad resistor would be a higher reading or no reading at all. Only use an original FORD made resistor as modern reproductions have been known to have issues. Regards, Kevin.
Click to expand...

My answer related to the original 1936 Ford flathead ignition system. You did not state that your coil was a canister type, which may or may not require a resistor in circuit. Regards, Kevin.
 
koates said:
My answer related to the original 1936 Ford flathead ignition system. You did not state that your coil was a canister type, which may or may not require a resistor in circuit. Regards, Kevin.
Click to expand...

Hi Kevin. It is a later 'can' type or 'cylinder' coil not the helmet coil as original. The motor is out of a '46 Ford and has the crab style distributor cap.

I ordered up a NAPA FA54 condenser I need a new one anyway mine has a bad wire lead somebody wrapped it in electrical tape it looks frayed and worn, they will have it in Wednesday.
 
Also check the coil. Many aftermarket "can" type coils state right on the can if it requires a resister or not.
 
Update on my 'no-fire- on the 59AB Flathead. 6V Pos. ground as original.

Coil has a resistor built in, 6V checks at 1.5 Ohms on the primary side. There is also an external resistor under the dash as original. Tried another coil also 1.5 Ohms no difference in starting. ( It has been wired this way for the last 2500 miles I have driven the truck!)

Changed condensor with a good one. No difference.

I am getting 6.1 V at the ignition switch, 6.1 V on both sides of switch w/ key on.

6.1V at the resistor on both ends. Power shows at the coil, and at the condensor w/ key on.

Voltage drops to 4.2 V across the coil and holds at 4.2V to the condensor.

I have to run errands Friday, will get back to the truck as soon as I can. I guess at this point it's either a bad coil wire or the points are closed up or something along that line.

Thanks for the tips I'll let you know what I find
 
You do not use an external resistor with a 1.5 ohm coil in a 6v system, how it was wired before is not relevant, it is not correct. There could be another issue as well, but the resistor in the circuit is sure not helping any! It is increasing the voltage drop (reducing the current flow in the circuit).

The under dash resistor was intended for use with a .7 to .8 ohm coil, it does not work with a 1.5 ohm coil.
 
JSeery said:
You do not use an external resistor with a 1.5 ohm coil in a 6v system, how it was wired before is not relevant, it is not correct. There could be another issue as well, but the resistor in the circuit is sure not helping any! It is increasing the voltage drop (reducing the current flow in the circuit).

The under dash resistor was intended for use with a .7 to .8 ohm coil, it does not work with a 1.5 ohm coil.
Click to expand...

I will try the re-wiring soon that you suggested. What puzzled me was the 2500 miles or so I have driven this truck wired like that and it ran really well. When it died Saturday it was a slow death, like it was fuel starved. I feathered the gas pedal and played with the choke and made it about a mile before she went completely dead.

Jim Linder has been dealing with some health issues as we know, I was hoping to send the distributor over to him to have him check it out. I'll have to ring him up and see if he's up for it. He is about the best;) Bubba's Ignition rebuilt this dissy probably ten years ago. I'm thinking the points are boogered up by now and I don't have a way to set them if I put new ones in.
 
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"6.1V at the resistor on both ends."
That makes me think the resistor has already been jumped, has already been by-passed.

"Voltage drops to 4.2 V across the coil and holds at 4.2V to the condensor."
That has me puzzled. Shouldn't voltage on the distributor side of the coil give a voltage reading of 0 ? Isn't it going to ground through the points? Seems like there should be nothing to hold potential in that wire, is going directly to ground.
 
JSeery said:
True, but was assuming it was a standard 1.5 ohm 6v coil. As flatjack posted, it is always best to check.
Click to expand...


What flatjack said. 4 volts at the coil is best.


My understanding is it does matter how you wire the coil +/- poles.
 
Tinker said:
What flatjack said. 4 volts at the coil is best.
My understanding is it does matter how you wire the coil +/- poles.
Click to expand...

Is there some confusion here? Voltage to a 1.5 ohm coil should be full system voltage, 6+ volts. You may be thinking of the voltage to an original distributor mounted coil.

I have never checked it, but the claim is reversing polarity at the coil results in about 80% loss of coil output. For a positive ground vehicle it should be supply voltage from the ignition switch connects to the (-) terminal and the (+) terminal connects to the distributor (points/capacitor).
 
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