Hello

I have a carrier 58FGA gas furnace and UPM programmable thm302M thermostat. House is resale and am not able to contact the previous owner.

I tried contacting upm but no luck.

Received low battery warning. Replaced battery and pushed reset button.

Thermostat has started to make an audible click on start up (and guess at end of cycle). Never did this before.
Right after the click there is a loud clunk (sounds like coming from furnance).

Thought maybe batteries at fault. So I replaced batteries( 2 AA alkaline) and reset to factory direct setting for thermostat. Unfortunately, this did not resolve the issue.

Any help/ info is greatly appreciated.

Thanks

A click at the thermostat is normal, but a clunk is not. Makes me think your hearing the duct work pop. Check to see if you have a dirty filter at the furnace or at the filter grill.