My 18 year old 75 BTU Tempstar furnace the Gas valve has three wires .

One ,to open the pilotgasvalve and two to open the main gasvalve!
I am not getting a pilotlight gas! Or lit one !

How to you check for voltage (24 V) on that incoming wire ?with my volt meter !

Should I replace the Burnerpilot/ignitor/sensor ?at same time ?

Will someone explain the function of the Pressure switch on that unit !

Tempstar sears model 867-769426

First remove and check your pilot orifice. It could be plugged up not allowing gas to pass through so the pilot will not light.