The Ford Barn

40cpe · 07-29-2015, 01:02 PM

My friend and I are still chasing a problem with a 6 volt '41 distributor. It gets 2.5 volts at coil with points closed and engine off, 3.8 V with engine running. When cold it starts right up and runs rather well, not perfect. New points at .015 by owner, new coil and condenser suppled by owner. We tried 2 different ICR 40 resisters. Battery voltage 6.1V. After driving a 5 miles or so, the running becomes progressively worse. It won't start when warm except with the resistor bypassed. We haven't driven it until it quits, but I suspect it will. We installed a temp 6V wire through a switch to the coil. Momentarily witching it on when it starts running badly helps, but doesn't cure it. The coil is too hot to hold your hand on after this 5 mile run. The 6V feed was only used momentarily so I don't think it is the cause of the heat.

Questions: Is it normal for the coil to be too hot to hold (120 degrees +)? Does skip only rebuild original coils? Does he have cores? Does he rebuild distributors? I know we could contact him, but he is busy and I won't bother him if he can't help with our situation.

Thanks for your feedback.

JSeery · 07-29-2015, 01:39 PM

Yes I think Skip has cores. But something is wrong with the wiring and/or parts. If the coil is working properly it will not get hot on low voltage. High voltage is what overheats a coil. Also, a new coil (or any other distributor parts) is not going to solve a low voltage to the coil issue. You should be getting 3.5 to 4.0 volts to the coil. If not, something is wrong with the wiring or some other component in the circuit. Need to find the problem and fix it. I would start by checking the voltage at the battery, then at the CB panel, then the ignition switch (both in and out) and then to the ignition switch side of the ballast resistor. There should not be any voltage drop to speak of all the way to the ballast resistor. Also, the battery should be a little more than 6.1V.

If all of this checks out then you need to check the coil resistance. Is it the proper coil for a 6v system? If it is a later model coil it shouldn't need a resistor and that could be the issue. You want around a maximum of 4 amps through the points. The ballast resister should be (I think) around .5 ohms and you want around 1.5 ohms total (coil and resistor). Most modern coils are ether 1.5 ohm or 3.0 ohm coils. 3 ohms won't work at all, 6/3 = 2 amps (this is with no resistor!). A 1.5 ohm coil with no resistor would be 6/1.5 = 4 amps, about right. A 1.5 ohm coil with a .5 ohm ballast resistor would be 6/2 = 3 amps, marginal. With the ballast resistor the coil should be around 1 ohm, again 6/1.5 = 4 amps.

These are just rounded off generalized numbers, but should give you the idea. I would start by straighten out the wiring and check out what coil you are using and then work from there. If it is an 1.5 ohm coil I would try driving it with the ballast resistor by-passed permanently (for a while) and see what happens. A 1.5 ohm coil should not over heat on 6v.

Kahuna · 07-29-2015, 02:26 PM

Excellent explanation, J.
Good job

40cpe · 07-29-2015, 03:21 PM

Thanks JSeery for your in-depth reply. I agree that the coil shouldn't heat under normal conditions. This, and the progressively deteriorating running condition, is the reason I'm asking. I have checked all the items you have mentioned. The battery voltage is 6.1 right up to the distributor with the points open. It drops to 2.5 with them closed. it is at 3.8 with the engine running, so it should be running OK with that voltage?? I've mentioned in other posts that this car has a new harness, switch, resister, coil, points. All connections checked to be tight. Voltage does drop to 5.9 when points are closed and is constant from battery to input of resistor. It starts fine like this until the ignition heats up. Will start fine with engine heated with by-pass of the resistor. The coil has 1 ohm resistance. One thing I didn't check is the amperage drawn at the coil. I'll get that reading. Because of all this, I've suggested getting the ignition system professionally checked on the proper machinery so we KNOW everything is correct. I would love to get it all to one location for the repairs for obvious reasons.

JSeery · 07-29-2015, 03:51 PM

First question would be how can it have 6.1v at the coil with ballast resistor connected?

40cpe · 07-29-2015, 04:33 PM

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There is no load on the resistor with the points open.

07-29-2015, 01:02 PM	#1
40cpe Senior Member Join Date: May 2010 Location: Star, MS Posts: 4,025	'41 helmet distributor My friend and I are still chasing a problem with a 6 volt '41 distributor. It gets 2.5 volts at coil with points closed and engine off, 3.8 V with engine running. When cold it starts right up and runs rather well, not perfect. New points at .015 by owner, new coil and condenser suppled by owner. We tried 2 different ICR 40 resisters. Battery voltage 6.1V. After driving a 5 miles or so, the running becomes progressively worse. It won't start when warm except with the resistor bypassed. We haven't driven it until it quits, but I suspect it will. We installed a temp 6V wire through a switch to the coil. Momentarily witching it on when it starts running badly helps, but doesn't cure it. The coil is too hot to hold your hand on after this 5 mile run. The 6V feed was only used momentarily so I don't think it is the cause of the heat. Questions: Is it normal for the coil to be too hot to hold (120 degrees +)? Does skip only rebuild original coils? Does he have cores? Does he rebuild distributors? I know we could contact him, but he is busy and I won't bother him if he can't help with our situation. Thanks for your feedback.

07-29-2015, 01:39 PM	#2
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: '41 helmet distributor Yes I think Skip has cores. But something is wrong with the wiring and/or parts. If the coil is working properly it will not get hot on low voltage. High voltage is what overheats a coil. Also, a new coil (or any other distributor parts) is not going to solve a low voltage to the coil issue. You should be getting 3.5 to 4.0 volts to the coil. If not, something is wrong with the wiring or some other component in the circuit. Need to find the problem and fix it. I would start by checking the voltage at the battery, then at the CB panel, then the ignition switch (both in and out) and then to the ignition switch side of the ballast resistor. There should not be any voltage drop to speak of all the way to the ballast resistor. Also, the battery should be a little more than 6.1V. If all of this checks out then you need to check the coil resistance. Is it the proper coil for a 6v system? If it is a later model coil it shouldn't need a resistor and that could be the issue. You want around a maximum of 4 amps through the points. The ballast resister should be (I think) around .5 ohms and you want around 1.5 ohms total (coil and resistor). Most modern coils are ether 1.5 ohm or 3.0 ohm coils. 3 ohms won't work at all, 6/3 = 2 amps (this is with no resistor!). A 1.5 ohm coil with no resistor would be 6/1.5 = 4 amps, about right. A 1.5 ohm coil with a .5 ohm ballast resistor would be 6/2 = 3 amps, marginal. With the ballast resistor the coil should be around 1 ohm, again 6/1.5 = 4 amps. These are just rounded off generalized numbers, but should give you the idea. I would start by straighten out the wiring and check out what coil you are using and then work from there. If it is an 1.5 ohm coil I would try driving it with the ballast resistor by-passed permanently (for a while) and see what happens. A 1.5 ohm coil should not over heat on 6v. Last edited by JSeery; 07-29-2015 at 01:45 PM.

07-29-2015, 02:26 PM	#3
Kahuna Senior Member Join Date: May 2010 Location: NorCal Posts: 2,617	Re: '41 helmet distributor Excellent explanation, J. Good job

07-29-2015, 03:21 PM	#4
40cpe Senior Member Join Date: May 2010 Location: Star, MS Posts: 4,025	Re: '41 helmet distributor Thanks JSeery for your in-depth reply. I agree that the coil shouldn't heat under normal conditions. This, and the progressively deteriorating running condition, is the reason I'm asking. I have checked all the items you have mentioned. The battery voltage is 6.1 right up to the distributor with the points open. It drops to 2.5 with them closed. it is at 3.8 with the engine running, so it should be running OK with that voltage?? I've mentioned in other posts that this car has a new harness, switch, resister, coil, points. All connections checked to be tight. Voltage does drop to 5.9 when points are closed and is constant from battery to input of resistor. It starts fine like this until the ignition heats up. Will start fine with engine heated with by-pass of the resistor. The coil has 1 ohm resistance. One thing I didn't check is the amperage drawn at the coil. I'll get that reading. Because of all this, I've suggested getting the ignition system professionally checked on the proper machinery so we KNOW everything is correct. I would love to get it all to one location for the repairs for obvious reasons.

07-29-2015, 03:51 PM	#5
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: '41 helmet distributor First question would be how can it have 6.1v at the coil with ballast resistor connected?

07-29-2015, 04:33 PM	#6
40cpe Senior Member Join Date: May 2010 Location: Star, MS Posts: 4,025	Re: '41 helmet distributor Sponsored Links (Register now to hide all advertisements) There is no load on the resistor with the points open.