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Ignition Coil Internal Resistor

L

Lamentations

New User
I posted my problem a while ago at http://www.ytmag.com/ttalk/messages/881639.html
I guess that thread is dead, but the problem persists.
I'm wondering now if the coil on a Ford 3000 should have an internal resistor.
The original, which produces a weak spark is painted over.
The replacement, which does not generate a spark, has an internal resistor.
Primary circuit resistance...old 1.6 ohm
new 3.5 ohm
I cannot get a reading on secondary curcuit of either
(infinite ohm).
The parts sold online are no internal resistor.
I guess I could call the dealership, but I'm suspicious of their knowledge now.
Thanks to all replies.
 
With the ignition "ON", points closed, WHAT voltage are you seeing on the primary terminal on the coil that is connected to the ignition switch... if full "12 Volt" battery voltage, you need a coil with a primary resistance in the 3 - 4 Ohm range.

If the voltage measures in the 6 - 8 Volt range, that indicates there's a ballast resistor in the circuit and you can use a coil marked "Use with external resistance".

These voltage readings ASSUME the points are closed and making contact AND the primary of the coil is not "open". In other words, the primary circuit must be intact and flowing current or the voltage measurements will be meaningless.

As to the secondary resistance, it will likely be in the 6000 Ohms to 12,000 Ohms range, measured from either of the primary terminals.

<img src = "http://mgaguru.com/mgtech/ignition/pics/circ_ic.gif">

(There will be a tiny variation in the secondary Ohms reading depending upon from which primary terminal the measurement is made 'cause one way the primary resistance will be in series (added to) the secondary resistance.)
 
Sounds like either your ohm-meter doesn't read high resistance very well, or maybe you're checking from the wrong places?

Secondary resistance between either one of the primarys and the secondary (output to coil wire) should be 6,000 to 12,000 ohms depending on the coil.
 
Thers no room inside the coil for a 30 watt resistor.You adjust the wire size and number of wire turns when making a 12 volt coil.
 
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