in order to meter the voltage, you need to have it hooked to a load .... start with a resistance check with an ohmeter, not sure the resistance used for the heater, but if it's not an open circuit it's still usable .... if there's another for the gas gauge it'll be about 40 ohms

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics