Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 11-01-2011, 11:41 AM   #21
johnbuckley
Senior Member
 
johnbuckley's Avatar
 
Join Date: Jul 2010
Location: United Kingdom
Posts: 1,439
Default Re: 12 volt or 6 volt coil how to tell difference

Ok you lot, Slow witted limey here... most of us have kicking around our workshops a variety of coils like this....
a) coils for 12 volt non ballasted ignition circuits, b) coils for 6 volt ignition circuits, c) coils for 12 volt ignition circuits with a ballast resistor. d) so-called sports coils for 12 volt circuits.
Can we get a definitive answer between us as to how to identify each of them?
johnbuckley is offline   Reply With Quote
Old 11-01-2011, 11:59 AM   #22
Dave in Boise
Senior Member
 
Dave in Boise's Avatar
 
Join Date: May 2010
Posts: 330
Default Re: 12 volt or 6 volt coil how to tell difference

Quote:
Originally Posted by johnbuckley View Post
Ok you lot, Slow witted limey here... most of us have kicking around our workshops a variety of coils like this....
a) coils for 12 volt non ballasted ignition circuits, b) coils for 6 volt ignition circuits, c) coils for 12 volt ignition circuits with a ballast resistor. d) so-called sports coils for 12 volt circuits.
Can we get a definitive answer between us as to how to identify each of them?
Here's my take.. Very simple

a) coils for 12 volt non ballasted ignition circuits ---- will show 12 v out when put from one terminal to the other
b) coils for 6 volt ignition circuits ---- will show 6v out when 12v is put in one side
c) coils for 12 volt ignition circuits with a ballast resistor ---- will show 6v out when 12v is put in one side due to the internal resistor
d) so-called sports coils for 12 volt circuits ---- will show 12 v out when put from one terminal to the other.

Hope this Helps.

Dave
Dave in Boise is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 11-01-2011, 10:22 PM   #23
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
Default Re: 12 volt or 6 volt coil how to tell difference

Quote:
Originally Posted by Dave in Boise View Post
Here's my take.. Very simple

a) coils for 12 volt non ballasted ignition circuits ---- will show 12 v out when put from one terminal to the other
b) coils for 6 volt ignition circuits ---- will show 6v out when 12v is put in one side
c) coils for 12 volt ignition circuits with a ballast resistor ---- will show 6v out when 12v is put in one side due to the internal resistor
d) so-called sports coils for 12 volt circuits ---- will show 12 v out when put from one terminal to the other.

Hope this Helps.

Dave
You need current flow to get a voltage drop. If you apply x volts in you will get x volts out without current flow.

I find 12 volt coils are marked 12 volts on the case, but this still doesn't tell you if it should have an external resistor. I'd connect the voltage across the 2 primary termianls to determin if it needs an external resistor. If the coil draws about 3 to 4 amps then it shouldn't need an external resistor. If it draws more amps, then add a resistor to bring the current draw down to 3 to 4 amps.

BTW, the markings "DIST" and "BAT" on the coil primary termianls are useless unless you know what the coil was built for as far as battery ground.
Tom Wesenberg is offline   Reply With Quote
Old 11-02-2011, 08:21 AM   #24
MrTube
Senior Member
 
MrTube's Avatar
 
Join Date: Jun 2010
Location: New Jersey
Posts: 1,471
Default Re: 12 volt or 6 volt coil how to tell difference

Quote:
Originally Posted by Tom Wesenberg View Post
You need current flow to get a voltage drop. If you apply x volts in you will get x volts out without current flow.

I find 12 volt coils are marked 12 volts on the case, but this still doesn't tell you if it should have an external resistor. I'd connect the voltage across the 2 primary termianls to determin if it needs an external resistor. If the coil draws about 3 to 4 amps then it shouldn't need an external resistor. If it draws more amps, then add a resistor to bring the current draw down to 3 to 4 amps.

BTW, the markings "DIST" and "BAT" on the coil primary termianls are useless unless you know what the coil was built for as far as battery ground.
So does this all mean its just easier for most people to throw out unknown coils and simply buy a coil for the proper application?
MrTube is offline   Reply With Quote
Old 11-02-2011, 09:34 AM   #25
johnbuckley
Senior Member
 
johnbuckley's Avatar
 
Join Date: Jul 2010
Location: United Kingdom
Posts: 1,439
Default Re: 12 volt or 6 volt coil how to tell difference

Succintly.... YES!
johnbuckley is offline   Reply With Quote
Old 11-02-2011, 10:40 AM   #26
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
Default Re: 12 volt or 6 volt coil how to tell difference

Sponsored Links (Register now to hide all advertisements)
Quote:
Originally Posted by MrTube View Post
So does this all mean its just easier for most people to throw out unknown coils and simply buy a coil for the proper application?
No, as it's easy to check coil polarity, as has been posted on the internet by the Chicagoland MG club.

I know a lot of people consider changing parts the easiest way to go, but it isn't the cheapest way to fix the problem and often leads to more problems.

http://www.chicagolandmgclub.com/tec...neral/574.html

Last edited by Tom Wesenberg; 11-02-2011 at 11:04 AM.
Tom Wesenberg is offline   Reply With Quote
Old 11-02-2011, 11:47 AM   #27
johnbuckley
Senior Member
 
johnbuckley's Avatar
 
Join Date: Jul 2010
Location: United Kingdom
Posts: 1,439
Default Re: 12 volt or 6 volt coil how to tell difference

Aaaaah Tom, you've started us coil polarity again, you cad!
johnbuckley is offline   Reply With Quote
Old 11-02-2011, 12:03 PM   #28
RonC
Senior Member
 
RonC's Avatar
 
Join Date: May 2010
Location: Rhode Island
Posts: 1,868
Default Re: 12 volt or 6 volt coil how to tell difference

Quote:
Originally Posted by MrTube View Post
So does this all mean its just easier for most people to throw out unknown coils and simply buy a coil for the proper application?

A brand new 6 volt coil at autozone costs only $16.00. I guess it depends on what your time is worth expecially if that kicking around coil quits during your next tour.
RonC is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 12:38 PM.