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Old 03-14-2016, 07:48 AM   #1
arc40s
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Default Hot coil

Question:
I have a 8BA engine with 12V can coil.
Stock single point dist.
After about 56-60 miles the coil get so hot it start mis fire losses power and then just stops and wont start or run. change to new coil starts right up for another 60 miles and stops again.
coil has internal resistor.
tried one coil with out resistor same results.
What causes coil to become so hot it stops working and how do I keep things cool?
vehicle is 1940 Ford Pickup aluminum radiator. Temp of engine fine, normal range.
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Old 03-14-2016, 07:54 AM   #2
G.M.
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Default Re: Hot coil

Check voltage to coil when running it may need a bigger resistor. G.M.
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Old 03-14-2016, 08:13 AM   #3
JM 35 Sedan
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Default Re: Hot coil

Make sure it is connected in the circuit correctly. Sometimes folks will inadvertantly connect the electrical feed to the secondary coil terminal instead of on the primary side of coil. The engine will run this way, not well though, but the coil will overheat and eventually burn out.
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Last edited by JM 35 Sedan; 03-14-2016 at 10:25 PM.
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Old 03-14-2016, 09:49 AM   #4
arc40s
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Default Re: Hot coil

hot wire from ignition switch goes to + primary side of coil
- neg side off coil goes to distributor.

Hot HOt HOT
???? not sure what to do next.....

What should voltage be from ign switch to coil? using an internal resistor coil.

If using a external resistor before coil what should be voltage to coil + side read?

What size or application 12 voltcoil should work ok? 55 chevy ; 62 falcon; Dodge ??
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Old 03-14-2016, 09:59 AM   #5
Charlie ny
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Default Re: Hot coil

arc,
OK, if you are running neg ground the neg side of the coil is attached to the distributor, pos side to the ignition circuit. Further more since you have switched to
12v do yourself a huge favor and purchase a BOSCH blue coil, Bosch pt# 00012. this
beauty allows you to eliminate the resistor.
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Old 03-14-2016, 10:15 AM   #6
BUBBAS IGNITION
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Default Re: Hot coil

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Quote:
Originally Posted by arc40s View Post
Question:
I have a 8BA engine with 12V can coil.
Stock single point dist.
After about 56-60 miles the coil get so hot it start mis fire losses power and then just stops and wont start or run. change to new coil starts right up for another 60 miles and stops again.
coil has internal resistor.
tried one coil with out resistor same results.
What causes coil to become so hot it stops working and how do I keep things cool?
vehicle is 1940 Ford Pickup aluminum radiator. Temp of engine fine, normal range.
Actually the issue of heat is wattage. Wattage comes from resistance. Low resistance causes heat build up.Ex: Using a 1.5 ohm resistor AND a 1.5 ohm resistance primary coil the total resistance would be 3.0 ohms. 3.0 ohms divided into 14.6 volts of a running , charging engine would be 4.8 amps ( or less with some heat build up, causing resistance to increase). Amps xs the voltage= watts (or 70 watts in this example) This is approx normal amps for a ignition primary.

Now lets use the coil on my desk Pertronixs Flamethrower of .6 ohms resistance. 14.6 volts divided by .6 ohms would be 24.3 amps !!!!!!
OR 354.78 watts!!!!!!! Thats 5 times the amount of watts!
Happens every day..........cant do it !!!!!
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Old 03-14-2016, 10:39 AM   #7
arc40s
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Default Re: Hot coil

Whew... that was a lot for some how only reads the amount of watts it takes to burn my fingers while twisting two wire together.

So what coil do I need to stay cool?

if I have a neg ground system do I connect the ign wire to neg side of coil?
and dist wire to +positeive side of coil.

not what others recommended.
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Old 03-14-2016, 10:45 AM   #8
BUBBAS IGNITION
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Default Re: Hot coil

Quote:
Originally Posted by arc40s View Post
Whew... that was a lot for some how only reads the amount of watts it takes to burn my fingers while twisting two wire together.

So what coil do I need to stay cool?

if I have a neg ground system do I connect the ign wire to neg side of coil?
and dist wire to +positeive side of coil.

not what others recommended.
Neg ground is distributor to negative coil and ignition on off to positive.
The Bosch blue coil from amazon # 00012 is a 3.0 ohm coil and doesnt need a resistor. ( a great coil , never seen a bad one)
Another local option would be a napa IC12SB ( 1.5 ohm) with a ICR13 resistor ( also 1.5 ohms)
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Old 03-14-2016, 10:46 AM   #9
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Default Re: Hot coil

Remember, the points work by grounding the ignition circuit to complete it. For negative ground systems, negative pole on coil goes to the distributor, for positive ground systems, vice-versa. I think "Bubba" has already answered your "which coil" question.

Ooops! Sorry Bubba; I thought you may have been working, so I stepped in.
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Old 03-14-2016, 10:46 AM   #10
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Default Re: Hot coil

12v neg ground system, ignition (+) to (+) side of coil and the (-) side of coil to the distributor. If the coil is getting hot there is most likely more voltage (power, wattage) going to it than it was designed for. Either reduce the input (add resistor) or change the coil. The Bosch Blue coil if often recommended (see #5 above). Have you checked the resistance of your existing coil?

Note: Yep, see Babba post #8!
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