Our furnace will run, and after a few minutes the thermostat shuts off, comes back on, and a few minutes the furnace will shut off and then back on. My thermostat is connected to the C on the mainland, so I know the circuit board is restarting. Top of core looks fine, but I can't figure out if my secondary is cracked? It was installed in 2001.
I would need to run some tests to figure out why your unit is kicking off and on or witness what part of the cycle it's stopping. As for the heat exchanger, you'd probably need to have someone run a smoke or CO detection test and you're likely still to be under a parts warranty. Get a CO detector to be safe.
Updated on January 8, 2018
By Dan Robbins