The difference between Ballast and non Ballast coils.

 

 




⚡ Non-Ballast Ignition Coil:

  • No Ballast Resistor Used.

  • Voltage at Coil: Designed to run at full 12 volts continuously.

  • No Start Bypass Needed: It’s built to handle the full voltage without damage.

  • Common In: most Classic cars up to the 1970's



🔧 Ballast Ignition Coil:

  • Used with a Ballast Resistor (or a resistance wire).

  • Voltage at Coil: Normally runs at 6 to 9 volts during engine operation.

  • Starting Boost: During startup, the ballast resistor is bypassed so the coil gets a full 12 volts from the battery to help with cold starts and ensure a strong spark.

  • Purpose of Ballast Resistor: Limits current flow after starting to protect the coil and prolong its life.

  • Common In:  Fords from the 1968 on many Triumph models and in commpon use from the early 1880's

⚠️ If you remove the ballast resistor and run 12V full time to a ballast coil, it will overheat and eventually fail.


🔍 How to Tell the Difference:

  • Resistance Check (Primary winding):

    • Ballast Coil: ~1.5 ohms or higher.

    • Non-Ballast Coil: ~ 3 ohms (Higher resistance).

  • Labeling: Some coils are marked “Use with Ballast Resistor” or “12V” (non-ballast).