I have an 11-year old system with forced hot air furnace manufactured by Comfortmaker. It’s a second zone unit located in the attic of the house that I recently purchased. During home inspection, the inspector refused to test the furnaces after checking out the air conditioning function. His reason was that doing so will crack the heat exchangers.
Anyway, the A/C had been off for a while so yesterday I turned up the thermostat to test out the furnace. Air came out of the vents but no heat. I took the cover off and saw what happened. At first the draft inducer was running, next the spark/pilot was lit, and then the burner was on for about 2 to 3 seconds but immediately shut off. The furnace would repeat this sequence another time before stop trying. It appeared some anomalies were detected by certain sensors. The draft inducer kept running, although it made a scratching noise when operating. Not sure if this had anything to do with the issue.
Before I call a HVAC guy to look at it, I’d like to get a rough idea what is the likely cause of this. Don’t want to get charged for parts that are not really broken. Thanks for any help in advance.