Glow-spark plug

  • Turn heater off.
  • Unscrew plug and clean if dirty.
  • Install angled connector and ignition cable as well as grounded cable, then hold glow-spark plug with insulated pliers.
  • Turn heater on. Sparks must jump across from central electrode to casing (ground).


The electrode gap can widen during operation due to natural erosion. The prescribed gap is 0.98” (2.5 mm) and should be checked and then adjusted if necessary.


The required suppression resistance of 5 kOhm is installed in the glow-spark plug. If, when measuring the resistance with an ohmmeter, a reading of more than 10 kOhm is obtained, install a new plug.

  1. Ammeter
  2. 12 Volt battery

Test glow element for circuit. Connect ammeter as shown and apply 12 Volts from a battery. If there is a current of 5.5 to 7 Amps, the glow element is serviceable. If the ammeter gives no reading (open circuit) or a reading of more than 8 Amps is shown (short curcuit), install a new glow-spark plug.