The reason for using the oil pressure switch is to keep the choke heater from operating if the engine isn't running. It's not uncommon for a cold engine to stall during warm-up, and if it's not restarted immediately, the choke continues to heat as long as there's voltage coming from the ignition switch. That releases the choke coil and the engine is hard to restart. By switching the voltage off with the loss of oil pressure, the choke stays applied. It doesn't matter if you've got a non-electric oil pressure gauge- - - - -all it takes is a tee fitting to expose the switch to oil pressure. Wire one terminal of the switch to ignition voltage, and the other one to the choke coil. You're good to go!
Jerry
