I am having problems with my heating system/thermostat.(7 yo Carrier gas) I have my thermostat set at 73 or 75. It does not hold that temp; drops to 68 and then the furnace kicks on to bring it to 73 or 75 again. Setting temp higher does not kick it on. I've had the repair person out twice already, the first time he just changed the filter, system work for approx. 4 days then same trouble started again. On 2nd visit he replaced the "board", again it worked for about 4 days and I am back to the same probelem of it not keeping the set temp but dropping down to 68-70 before kicking on. I've had annual PM's done on this unit since I bought it.

After the 1st visit I also smelled burning plastic near the thermostat. The repair tech stated it was not my thermostat. This is getting very frustrating/expensive. Any suggestions/advice would be appreciated as single digit temps coming Wed. Help!

Carrier... model # ? Check the unit for a status/fault LED. If flashing, note the pattern and compare it to the legend on the service label (usually found inside access panel). Post results here.