The gas furnace is a Carrier 58sx100-cc-1. On start up it has no spark to
the pilot (3 wire). There is no gas from the gas valve going to the pilot.
So it never fires up. Pressure switch closes when inducer comes on. The
collector box port that feeds the pressure switch is not plugged. The othe
r hoses are open too. The exhaust and intake pipes for combustion are open.
What else to check? There is voltage to the spark igniter going in, but no
n coming out of the box, but these 2 terminals show continuity.