The Stovebolt Site Forums The Shop Area The Electrical Bay 1946 Chevy 1/2Ton - Ballast Resistor

I'm confused now. The problem the entire time was that the dizzy rotor wasn't installed? The ballast resistor was fine all along?

The missing rotor would not have caused the erratic electrical readings. It would however cause a no start issue.

Way to hang in there. Long wait but success. Glad to hear it is running. Looks like that ride is getting closing. This thread is a great learning tool also.

Ha!

Me too. Failure to install a rotor is not a mechanical thing. I followed this. How is this possible to forget a rotor??
Trying to learn about a 235 but this was little help.

Right. But there are two different threads and it's hard to follow. In the other thread Utah said the condenser was fried, which would cause a no start, no run condition. This problem occurred both with the resistor installed and without it installed.

Were the voltage readings relative to the ballast resistor accurate or valid? What ballast resistor is installed now with the engine running? The same one that was installed during the no start/ no run condition? A new one?

Were there two different problems?

Did one problem (missing rotor) supersede another problem (fried condenser)?

I probably wasn't very clear. At the very beginning when I first tried to start the engine, a fuse kept blowing. This fuse was from the starter to the ignition. It was suggested I change the wiring on my alternator so that the charge wire went directly to the battery +. I did that and tried to restart and the fuse was now holding, so rewiring helped that issue. I'm thinking when the fuse was blowing I may have shorted out the condenser, but didn't consider that option at that time because the voltage on the ballast resister was low. Yesterday, I was planning to start from scratch and reset top dead center, line up the BB on the flywheel, line up the rotor with the #1 spark plug, verify firing order,... But it was suggested I first swap out the condenser to verify it was working. I installed a new condenser and it fired up. I was just saying that yesterday after installing the new condenser, I put the cap back on and forgot the rotor at that time. I heard it fall off the fender when cranking and got it installed.

For those who can't follow along, here's a review. It wasn't the rotor that caused the no-start all along, but it needed to be removed to swap out the condenser.
John's rotor-on-the-fender comment was just an aside.

Sorry for the confusion guys!

Otto, I'll do some testing today to see if the voltage readings changed since I replaced the condenser. I'm using the original ballast resister at this time.

Tested voltage today and they are pretty similar to what I measured before.

Points Closed:
Battery to ignition was 12.34 volts
Key ON to ballast resistor was 11.96 volts
Ballast out was 5.34 volts
Coil+ was 5.34 volts
Coil- was 0.05 volts
Distributor outside and inside was 0.05 volts

Points Open:
Ballast IN/OUT to Coil+/- to distributor was 12.15 volts

What is meter on ohms, key off, points open, red meter lead to ignition switch of resistor, black lead to coil side of resistor?

Then move red lead to points side of the coil. What is the meter reading now?

2.0 ohms and then 1.4 ohms

I did pick up a different resistor today (#ECH ICR23) from NAPA that says it has 1.2 ohms of resistance, but when I measure it I get 1.6 ohms. I haven't tested it yet to see if it gives a little more voltage.

Assuming 1.4 ohms is correct for your coil, you need somewhere around 0.5 to 0.7 ohms for the resistor.

Tell us more about the coil. Manufacturer, part number, etc. 1.4 ohms sounds like it may be an HEI type coil. I'd expect the primary coil winding to be more like 3 to 4 ohms for a 12 volt points type coil.

Coil came with my 6v to 12v conversion kit. I don't know much about it. Maybe it was a good coil back in 2003, but maybe there are better coils today? I'm always open to ideas and suggestions.

Specs for this Mallory coil do show a 1.4 ohm primary. Jegs and Summit still sell this coil, but I can't find a web site for Mallory the company. I haven't been able to find a Mallory recommended ballast resistor resistance, but to get somewhere around 8-9 volts after starting the engine, you'd need around 0.6 ohms like I said above. And at this low resistance (0.6 + 1.4 = 2 ohms) I'll bet your points won't last long.

Me? I'd find a more "standard" coil like the Delco E552C ( $25.99 @ RockAuto) which is the recommended coil for a 1957 Chevy 235 truck among a bunch of other 12 volt GM vehicles with points ignition. Primary coil resistance is 3.1 ohms. Should work well with your ballast resistor, but isn't chrome plated like the Mallory coil.

Summit Racing website says the Mallory 29217 coil should work with a Mallory D1110-A ballast resistor.

Using the D1110-A ballast resistor rated at 1.8 ohms would bring the current through the points down to just under 4 amps. I'd still worry about life expectancy of the points. And the math just doesn't work out. Points closed, the voltage at coil + will be around 6.75.

The Mallory coil is meant for an engine capable of much more RPM and a couple more cylinders than your 235 has. Loose the chrome coil, gain reliability.

There is a lot of incest in the automotive industry. I think Holley now owns Mallory. Try Holley.com then click on Brands for Mallory.

Dennis

You're right, Dennis.

Holly owns Mallory, MSD, Mr Gasket, Lakewood, Flowmaster, Hooker Headers, Weiand, Accel, Edge, Simpson Racing, Hilborn, Hurst, Baer Brakes, ADS, Diablosport, and tons more.

I don't need a chrome coil. It was in the kit I purchased, so I was just using it.

Bill, I'm a little confused with the voltage. If I'm currently getting 5.34 volts through the ballast resistor to the coil+, is that not good for the points? I'm not running 12 volts to the coil+, I guess I'm confused with ohms vs voltage vs amps? I understand the 12 volts to the points is not good and I'm hearing 8 volts to 9 volts is better. Mine seems to be lower than that, so is that not better as long as the engine is running OK? Or, will that lower voltage come back to haunt me later?

Dumba$$ that I am, I thought there was a problem with how it ran.

I still think that the life of the points will be shortened with the hiperf coil and it's recommended ballast resistor.

Thanks for sharing your knowledge Bill. I will look into updating my coil. Ordering a kit years ago, you get what you get. No time like the present to make things work properly.

1959 3600 235 SM420

I also have ended up with a brand new ballast resistor outputting only 5.6V. I was converting my system back to an external resistor: new coil, new ballast resistor on the firewall, new connections.

Battery voltage 12.6, input voltage to the resistor 12.4V (from the key), output from the resistor 5.6V. Ohms across the resistor was 1.5 (actually 1.8 ohms if you test it for a couple seconds).

This resistor came from one of the big classic parts suppliers (I don't recall if it was Chevys of the 40's or Jim Carter or whomever, I get parts from all of them), so will see what's at NAPA on Monday.

Wouldn't Ohms and output voltage be correlated? Sub target voltage should mean that Ohms are abnormally high, but I though 1.5 was the ideal resistance?

1.5 ohms across the resistor is right IF the coil primary (coil + to coil -) measures about 2.4 ohms and you want the coil fed with 8.5 volts while running with 13 volts in the electrical system.

Math is like this:

Ballast Resistor ohms = Coil primary ohms / (13 / 8.5)

where 13 is the running voltage in the car and 8.5 is the target voltage desired on coil + when the points are closed.

Measure your coil primary ohms (coil + to coil -) with no wires connected to coil + and then plug that number into the formula to see what value you need for the ballast resistor. Unless your coil has a built-in ballast resistor. Then you don't need an external resistor AND the bypass wire does no good at all.

This electricity stuff is like magic . . .

Coil primary ohms in my new coil is 1.5, so I'm far off your target ohms of 2.4. My actual ballast resistor ohms are 1.8 (I measured too quickly, if I leave the test probes on the terminals for a second longer, the 1.5 ohm reading tics up to 1.8).

I found a lower ohm ballast resistor in stock that is 1.35 ohms, so I can use that, but with my coil testing at 1.5 ohms the ballast resistor would realistically have to be just 1 ohm to get a 4.5V drop when the car is running. Hmmm.

Not advertised as a ballast resistor, but something like THIS would do the job and look nice if you had a green truck.

Dang that's a fancy thing! Some RestoMod guy is gonna love that.

I think I'll go in search of a higher resistance coil to go with my lower resistance (1.35 Ohm) ballast. In my ignorance I just always assumed a coil was a coil and they came in 6V and 12V, with or without a resistor. Who knew they had so many flavors of resistance.

Viva La Resistance!!

If you want a higher current capacity, use two resistors wired in parallel, with twice the resistance value of a single one- - - - -for instance to get 200 watts power handling capacity and 2 ohms of total resistance, wire two 100 watt/4 ohm resistors in parallel. Ohm's stuff is a law, not a suggestion!
Jerry