If you get a snap disk style of thermoswitch from an appliance repair house and install it on the return line you can have the glowplug heater cycle to maintain consistent heat. Snap disk switches are available in different trigger temperatures and you simply use one to drive a relay to power the heater. Snap disks are used in water heaters and the like. This is one of Dana Linscotts ideas. It is not dangerous to use a glowplug heater provided its properly controlled. RT

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