Primary Ignition Test Procedures

To quickly check Ignition Coil Primary we recommend the following:

Ignition Coil - Primary

Using a Labscope


A labscope can be used to check the Ignition Primary Circuit when used with a Low Amp Clamp.   We recommend a Low Amp Clamp because the conversion of each amp to 100 mV gives the technician a detailed large waveform to evaluate.  High Amp Clamps will output only 1 mV per amp.  The resulting waveform can be small and not reveal necessary details of each pulse.


Proper testing of primary ignition using a labscope with an amp clamp can reveal an O.K. or problem system in seconds.

Remember… when the amps measured from millisecond to millisecond are right the resistance and voltage must also be right. 


The control setups for labscope voltage, time, triggering and acquisition mode, etc. as well as the type of connector banana or BNC, the voltage range limitations of the scope and switchable output choices of the Amp Clamp will all play a part in properly setting up the   instrument to do proper testing.




Automotive Scope Applications

 for detailed recommendations


Ignition Coil - Primary Resistance

Using a DMM

1. Disconnect connections to vehicle ignition coil.

2. Set meter to measure Ohms "".

3. Connect meter probe tips together and press "REL" to zero the reading.

4. Connect black COM lead probe tip to coil negative terminal.

5. Connect red Volts/ lead probe tip to coil positive terminal.

· Most specifications call for under 1 of resistance in the primary circuit of the coil.   Verify the specifications for the specific coil being tested.

· Resistance over specification will usually result in weak spark.

· Infinite resistance means an open circuit.