Four dimensions in the right order
A universal igniter must fit in four respects, and the order saves time. First the mounting, because an igniter with thread, flange or sleeve cannot be replaced with another type. Then the diameter, which determines whether the igniter can fit into the hole at all. Then the length, which determines the position in the burn pot, and finally the power in watt.
Most universal models are classic steel igniters and are named by diameter x length followed by watt. On flange models, two diameters, for example 9.5 / 14 mm, indicate the ignition surface and the flange. If the stove requires an adapter between the thread and igniter, there are igniter adapters with 3/8" thread. If you know the brand and model, it is quicker to start with the complete range of igniters.
Diameter and length
Measure the diameter with calipers. In the range, 9.5, 9.9 and 10 mm are so close that a ruler cannot distinguish between them, and an igniter that is half a millimetre too thick will not fit into the hole. The length is measured from the tip to the thread hexagon, to the flange or from end to end on smooth models. It determines how far the ignition tip reaches into the burn pot, so an igniter that is too short can result in slow or unsuccessful ignition.
If the old igniter is loose or crooked, the holder may be worn. A new igniter holder ensures that the new igniter is positioned in the same place as the old one.
When watt is not stated on the igniter
If the power is not stated on the old igniter, it can be calculated if it is a steel igniter. The heating coil is made of nickel-chromium, whose resistance changes by only a few percent from cold to hot, so a measurement with a multimeter provides a useful figure. Disconnect the igniter from the stove with the power switched off, and measure the resistance between the two wires. At 230 volt, approx. 212 ohm corresponds to 250 watt, 176 ohm to 300 watt, 151 ohm to 350 watt and 132 ohm to 400 watt. A cold measurement is normally slightly below the figure, so choose the closest power rating.
The method only works on steel. A ceramic igniter has a resistance that changes significantly with temperature, so a cold measurement does not indicate the power. Here, dimensions, shape and position determine the choice.
