I bought a house with the THM501 programmable thermostat 4 months ago. No problems until two nights ago. The low battery alarm kept going off - a high beeP (that kills my dog) and a female voice. The house heat was dropping fast. I changed the battery from Panasonic carbon AA to 8X ultimate Eveready AA
The alarm still keeps going off but the house heat is okay.

What can I do?

Sometimes it works. Turn off breaker to the furnace for a few minutes, and back on, this might reset everything