Performing integrity checks on climate control system components

A furnace system comprising:

• an igniter;
• and
• a controller including an igniter relay, and a current sensing circuit connected across the igniter and configured to sense, independently of the igniter relay, a current level through the igniter, the controller configured to sense voltage between terminals of a second relay of the controller;
• the controller further configured to:
• in a given one of a plurality of operational phases of the system, compare the sensed current level through the igniter and sensed voltage across the second relay to a current level and voltage associated together with a specific condition of the igniter, igniter relay, or second relay in the given phase, the comparing performable using a processor of the controller;
• and
• based on a result of the comparing, distinguish between a failure of one of the relays and a failure of the igniter.

A controller for an HVAC or furnace system having a gas igniter and a humidifier, the controller comprising:

• an igniter relay for controlling the igniter, and a current sensing circuit connected across the igniter and configured to sense, independently of the igniter relay, a current level through the igniter;
• the controller configured to:
• sense voltage between terminals of a humidifier relay for controlling the humidifier;
• based on the sensing performed after a call for heat and prior to a pre-purge of the system, determine whether the humidifier relay is welded;
• based on the sensing performed after pre-purge begins and before igniter warm-up, determine whether the humidifier relay is open and determine whether the igniter relay is welded;
• and
• based on the sensing performed when the igniter is warming up and before a gas valve of the system is energized, determine whether the igniter is operating normally, determine whether the igniter is open, and determine whether the igniter relay is open.