Ignition Coil Testing/Troubleshooting
Standard single output points type coils (Lucas/PVL, etc.), as fitted to most British motorcycles
With the aid of a multimeter, set to Ω (ohms) and measure coil resistance readings, as follows:
- Check primary resistance reading. The meter should be set to the low ohms setting, e.g. Ω x 1, 200 ohms, or similar range.
Connect meter probes onto the plus and minus (low tension) terminals.
A 12 volt Lucas type coil (or equivalent), has a nominal resistance of around 4 ohms, but acceptable readings will be in the range 3.8 - 4.5 ohms.
A 6 volt Lucas type coil (or equivalent), has a nominal resistance of around 2 ohms, but acceptable readings will be in the range 1.5 - 2.2 ohms.
Note: to get the most accurate reading, short the meter probes together and note the reading. This will show the internal resistance of the meter/probes, if any.
Subtract this reading from the coil reading, to give the true resistance reading of the coil. - Check secondary resistance reading. The meter should be set to the a higher ohms setting, e.g. Ω x 1000, 20K ohms, or similar range.
Connect one meter probe onto either the plus or minus (low tension) terminal. Connect the other meter probe onto the center (high tension) outlet.
If you would prefer not to remove the h.t. lead (plug wire) from the coil, the meter probe can be inserted into the end of the h.t. lead (unscrew plug cap first).
If the h.t. lead is copper cored (non resistive), then the reading at the end of the lead should be the same as measuring directly at the coil outlet (as copper cored lead has negligible resistance). If the h.t. lead is resistive, then it would be best to unplug it from the coil, to get the most accurate coil reading.
Typically, the secondary resistance reading for Lucas type coils is 10K ohms ±10%. - Check for insulation breakdown. The meter should be set to the a high ohms setting, e.g. Ω x 1M, 20M ohms, or similar range.
Connect one meter probe onto either the plus or minus (low tension) terminal. Connect the other meter probe onto metal casing of the coil.
This should be an open circuit (no meter reading). If you see a resistance reading, it would indicate a short between the primary winding and the case of the coil.
This is often results from damage/creasing to the casing. This is quite common on Norton Commando motorcycles, where the coil clamps were over-tightened in the factory.
Standard dual output points type coils, commonly fitted to British twin cylinder and single cylinder (twin-plug head) motorcycles, e.g. Pazon part# IC32/IC33/IC35
With the aid of a multimeter, set to Ω (ohms) and measure coil resistance readings, as follows:
- Check primary resistance reading. The meter should be set to the low ohms setting, e.g. Ω x 1, 200 ohms, or similar range.
Connect meter probes onto the plus and minus (low tension) terminals.
A 12 volt dual output type coil will typically have a primary resistance in the range 3 to 5 ohms.
A 6 volt dual output type coil will typically have a primary resistance in the range 1.5 to 2.2 ohms. The actual reading will depend on the brand.
Some coils will have the primary resistance marked on the body of the coil. If not, check with the supplier/manufacturer for the correct technical specification for your coil.
Note: to get the most accurate reading, short the meter probes together and note the reading. This will show the internal resistance of the meter/probes, if any.
Subtract this reading from the coil reading, to give the true resistance reading of the coil. - Check secondary resistance reading. The meter should be set to the a higher ohms setting, e.g. Ω x 1000, 20K ohms, or similar range.
Connect the meter probes into the h.t. (high tension) outlets.
If you would prefer not to remove the h.t. leads (plug wires) from the coil, the meter probes can be inserted into the ends of the h.t. leads (unscrew plug caps first).
If the h.t. leads are copper cored (non resistive), then the reading at the end of the leads should be the same as measuring directly at the coil outlets (as copper cored lead has negligible resistance). If the h.t. leads are resistive, then it would be best to unplug them from the coil, to get the most accurate coil reading.
Typically, the secondary resistance readings for dual output coils will be in the range 12-18k ohms. The actual reading will depend on the brand.
Check with the supplier/manufacturer for the correct technical specification for your coil.
Digital type ignition coils, as supplied with Pazon Smart Fire ignition systems
With the aid of a multimeter, set to Ω (ohms) and measure coil resistance readings, as follows:
- Check primary resistance reading. The meter should be set to the low ohms setting, e.g. Ω x 1, 200 ohms, or similar range.
Connect meter probes onto the plus and minus (low tension) terminals.
The single & dual output digital type coils have have a nominal resistance of 0.6 ohms.
Note: to get the most accurate reading, short the meter probes together and note the reading. This will show the internal resistance of the meter/probes, if any.
Subtract this reading from the coil reading, to give the true resistance reading of the coil. - Check secondary resistance reading. The meter should be set to the a higher ohms setting, e.g. Ω x 1000, 20K ohms, or similar range.
For the single output type coils (IC11/IC21), connect one meter probe onto either the plus or minus (low tension) terminal.
Connect the other meter probe into the high tension outlet.
If you would prefer not to remove the h.t. lead (plug wire) from the coil, the meter probe can be inserted into the end of the h.t. lead (unscrew plug cap first).
If the h.t. lead is copper cored (non resistive), then the reading at the end of the lead should be the same as measuring directly at the coil outlet (as copper cored lead has negligible resistance). If the h.t. lead is resistive, then it would be best to unplug it from the coil, to get the most accurate coil reading.
Typically, the secondary resistance reading is in the range 8-8.7K ohms.
For the dual output type coils (IC12/IC22), connect the meter probes into the h.t. (high tension) outlets.
If you would prefer not to remove the h.t. leads (plug wires) from the coil, the meter probes can be inserted into the ends of the h.t. leads (unscrew plug caps first).
If the h.t. leads are copper cored (non resistive), then the reading at the end of the leads should be the same as measuring directly at the coil outlets (as copper cored lead has negligible resistance). If the h.t. leads are resistive, then it would be best to unplug them from the coil, to get the most accurate coil reading.
Typically, the secondary resistance reading is in the range 8-8.7K ohms.