Natural gas, 17 years old. I power on, fan blower running - about 30 seconds later i hear a click and nothing. In the past, i'd hear it light up at this point. Heater does this 3 times. I smell a little gas, which was normal. Couple minutes later IF service code.Natural gas or propane?
How old is the heater?
Can you describe exactly what happens from the time you power the heater on?
Probably need to check the gas pressure.
You can check the ignitor with a meter by measuring the ohms at the 2 leads coming from the ignitor. An older silicon carbide ignitor ( shiny crystalline and fragile ) will normally ohm out at 45-150 ohms. A newer silicon nitride ignitor ( Looks like a smooth dull black matchstick ) will normally ohm out at about 11-17 ohms. A reading of 0 ohms means the ignitor is open and won't heat up.