Carpenter Ignition Coils

[BUBBAS IGNITION]

Kinda of a question regarding a New "script" replacement ignition coil from Dennis Carpenter.
Got one in for a distributor rebuild from a restro shop and it came with a new coil.
Coil looks nice and tests nice on machine under load with 6 volts applied.

Our issue is the primary resistance checks out at 8-9 ohms on the primary.
We checked a box full of other coils and they all checked from .6 ohms to .9 ohms. All were less than one ohm ?

Any ideas from the crowd. ????????

Like we stated the coil has good output and test very good under a loaded test??????

[BUBBAS IGNITION]

Called Carpenter and was put thru to the engineer thats handles the coils.
He said he had noticed that the coil was higher in resistance than the factory ( not lower) and they seemed to work very well.
Like i said above it doesnt seem to be a problem just a little unusual ???

[rotorwrench]

That's a pretty fair amount of resistance even by comparison to the can type coil in my 51 Merc at 1.05 Ohms @ 75 degrees F and it doesnt use a ballast. I wonder what the secondary resistance would be with that coil? It would be interesting to see how much the current draw is and how much temperature it would build under normal operating conditions?

[BUBBAS IGNITION]

Originally Posted by rotorwrench

That's a pretty fair amount of resistance even by comparison to the can type coil in my 51 Merc at 1.05 Ohms @ 75 degrees F and it doesnt use a ballast. I wonder what the secondary resistance would be with that coil?

Secondary is 8,000 ohms ........

[JM 35 Sedan]

What about a comparison ohms reading on the secondary windings of both coils? Perhaps these Carpenter coils have been wound to handle a voltage range, i.e. maybe 6 to 12 volts, instead of just 6V. I also saw those in his catalog and wondered who wound them. Thought maybe Skip was doing them.

[BUBBAS IGNITION]

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Checking my shop box of used coils they range anywhere from 4000 to 7500 ohms secondary resistance.......

[ken ct]

Originally Posted by BUBBAS IGNITION

Checking my shop box of used coils they range anywhere from 4000 to 7500 ohms secondary resistance.......

An interesting thread Jim,wonder where he's getting them made?? Anymore tidbits on them? ken ct.

[rotorwrench]

I know the old can type coils have a 4000 Ohm secondary at 75 degrees F. I don't know about the older iron core coils. That leaves more questions about condensers and allowable systems voltages for sure.

[jdl]

Originally Posted by BUBBAS IGNITION

Kinda of a question regarding a New "script" replacement ignition coil from Dennis Carpenter.
Got one in for a distributor rebuild from a restro shop and it came with a new coil.
Coil looks nice and tests nice on machine under load with 6 volts applied.

Our issue is the primary resistance checks out at 8-9 ohms on the primary.
We checked a box full of other coils and they all checked from .6 ohms to .9 ohms. All were less than one ohm ?

Any ideas from the crowd. ????????

Like we stated the coil has good output and test very good under a loaded test??????

From the 49-51 Ford shop Manual...primary resistance 1.05-1.15 ohms (75*) secondary resistance 4100 ohms (75*) amperage draw engine stopped 5.0-5.5 engine running 2.75-3.00

[BUBBAS IGNITION]

Originally Posted by jdl

From the 49-51 Ford shop Manual...primary resistance 1.05-1.15 ohms (75*) secondary resistance 4100 ohms (75*) amperage draw engine stopped 5.0-5.5 engine running 2.75-3.00

I guess i should have mentioned that this coil is for the two bolt 41 Ford Helmet distributor......distributor mounted coil......front of engine etc....

[Terry,OH]

With less than one Amp through the points they should last a long time.

[L78CHEVELLE]

I'm not a professional only a customer of the Dennis Carpenter coil. I purchased one and used it on my 1940 Ford. Coil lasted four months and went completely dead. I got out the old 70 year coil and installed it to get home.

[George/Maine]

I see the new coils are about half the cost of and old rebuilt one.
The ford coil had a .5 ohms resister and 3 amps in circuit=1.5 volt
leaving 3.5 volts thats left from 6 volt.
The true ohms is about 1.1 ohms.
With a mix of the 2 coils pri sec.
The new coil are most likly made from different wire
and winding not same.
IT would be better to test the voltage across .5 ohm
Voltage divided by.5= amps current.
say 1.2 volts dividered by .5 ohms=2.4 amps

[bk53]

had a carpenter 6v coil on my 53 f100. big mistake. I wasted several hours going thru everything else because "It couldn't be my brand new coil". I'll never buy another.

[George/Maine]

53 f100 has round coil and easier to find if your a purist only ford will do but any 6 volt will do. Try and get and old napa echlin ,no inports even if new.

[Inherited40tudor]

I've heard from several old timers that the distributer mounted coils break down quickly from the heat and recover after cooling down. Alot of them (me included) use the coil adapter kit with the coil mounted on the inner fender for running around. Easy to put old coil back for events. But you have to bypass the resistor under the dash for the cranking voltage drop.

[dh]

Just get the coil rebuilt by skip, I have 9000 mi on one , last check $75 Don

[G.M.]

The old Ford coils had problems from when the cars were new. You heard of vapor lock well 95% of vapor lock was a hot coil. It takes 20 minutes to change a fuel pump. This allowed the coil to cool and the engine restart thinking the pump was the problem. In the 30's and 40's the insulation on the magnet wire wasn't very good and would allow a small leakage of high secondary voltage lowering the output spark when they get hot. Modern materials prevent this leaking. Skip uses the best material to prevent this. He has done over 18,000 old Ford coils with very few failures and has never charged anyone to repair one if it failed since he has been doing them. They all start in weather conditions well over 100 degrees. I would say this is the most reliable coil you could install on any old Ford including a modern coil with an adaptor. Ask anyone who has one. All old original coils start when cold but EVERONE breaks down on a coil test machine when when hot. When your engine is cold check the spark from a plug wire to to a head nut it will jump a 1/2" with a good blue color. Get the engine real hot for at least 20 minutes and check again. You will see a weak yellow spark which will hardly start the engine. When it gets down to a small yellow ball the compression blows the arc out across the plugs. G.M.