coil question

gkgeiger

gkgeiger

Senior Member
I was reading through my V8 Times and got to the Tech section where I read about the markings on a tube style coil. The person asking the question had a 51 Crestliner and was going to replace the coil. His old coil had Bat and Dist for terminal markings. The replacement has + and - as does mine. He asked if the + marking was the same as Bat on the old.

Cecil's response was "Assuming you still have the factory positive ground system on your car, the "+" terminal should be connected to the distributor and the "-" terminal should be connected to the ignition switch. In other words: Bat = Negative and Dist = Positive."

I connected my new coil "+" terminal to the ignition switch. The car starts and runs fine. Could this be why my original coil failed? Should I switch the wires, or?
 
With a Positive battery ground the + mark on the coil should go to distributor and through the points to ground. The - mark on the coil should go to the ignition switch through the resistor. G.M.
 
gkgeiger said:
Thanks, have I done any damage? It's been 300 miles since I installed the new coil.
Click to expand...


Two things happen when the coil is hooked up backwards.
1-Being as the coil is a "tapped transformer" it looses as much as 80% of its reserve power. This makes the car need a tune up quicker as theres no ( or very little reserve output ) . A couple times over the years a oem vehicle left the factory wired backwards. May run ok but over time wont provide the spark needed.

2-The residual magnetism of the center iron core is also reversed per design and cant be reversed. Once a coil is running backwards for a period of time it cant be simply reversed.....

I just tested the output of a positive ground coil yesterday, tested good using a positive ground, reversed the leads and the coil had very little output.....:eek::D
 
BUBBAS IGNITION said:
Two things happen when the coil is hooked up backwards.
1-Being as the coil is a "tapped transformer" it looses as much as 80% of its reserve power. This makes the car need a tune up quicker as theres no ( or very little reserve output ) . A couple times over the years a oem vehicle left the factory wired backwards. May run ok but over time wont provide the spark needed.

2-The residual magnetism of the center iron core is also reversed per design and cant be reversed. Once a coil is running backwards for a period of time it cant be simply reversed.....

I just tested the output of a positive ground coil yesterday, tested good using a positive ground, reversed the leads and the coil had very little output.....:eek::D
Click to expand...
So, what would you recommend I do? I just reversed the terminals and it started right up and appears to run well.
 
BUBBAS IGNITION said:
Two things happen when the coil is hooked up backwards.
1-Being as the coil is a "tapped transformer" it looses as much as 80% of its reserve power. This makes the car need a tune up quicker as theres no ( or very little reserve output ) . A couple times over the years a oem vehicle left the factory wired backwards. May run ok but over time wont provide the spark needed.

2-The residual magnetism of the center iron core is also reversed per design and cant be reversed. Once a coil is running backwards for a period of time it cant be simply reversed.....

I just tested the output of a positive ground coil yesterday, tested good using a positive ground, reversed the leads and the coil had very little output.....:eek::D
Click to expand...

I just installed a new 12v coil, actually a NOS old coil, Standard Blue Streak FD-471, says for 1955 -1965 Ford, Lincoln, Mercury. This truck is all 12v, I have the - post connected to ballast resister on firewall, and + side to the distributor, it started up just fine, that's all I've done, haven't driven it since. Is this connection correct?
 
Well heck, I hooked it up like the old one came off, I didn't know if it would run either way or not. I found this on internet, I better switch mine around!
 

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After FoMoCo and the other major manufacturers went to 12-volt negative ground, the coils started being marked with polarity instead of component ID. This lead to a lot of problems with service parts back in that time frame. There is a pencil lead test at the high tension lead to check polarity but you can also purchase a polarity tester that has a little window to see the spark reaction. The tester plugs in line with the high tension lead. They are still available form several early Ford parts suppliers.

I have heard of coils that were not correctly marked for polarity but I guess it depends on the manufacturer whether they check them or not. In this day and age it pays to check everything with a healthy dose of skepticism.
 
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