Carrier HP (10 yrs) with NG backup. AH running continuously. Clicks noted in "controller box" outside of AH/furnace-turned to loud buzzing this AM. Switching unit off and on with rest stopped buzzing but air handler still running cont. Also the furnace is firing when the HP should be running. No activity noted from HP. Furnace seems to cycle a bit too frequently and erratically. Is this a relay problem? There are 3 relays...which ones are bad? Where is a good source for replacements? (This is a York control panel to a Borg Warner AH unit).