Dear Sir, I have a heating unit it will work sometime but it will not turn on sometime like the other night when it got below in the low 50 it came on for two day's mow it will not come on for a few more day's when it drop's below in the low 50 it work's sometime then not off and on can you help me are do you need more of the problem thank-you David

What model is your A/C Heating unit? Please provide...

Dear Sir, i have a heating unit it will work sometime but it will not turn on sometime like the other night when it got below in the low 50 it came on for two day's mow it will not come on for a few more day's when it drop's below in the low 50 it work's sometime then not off and on can you help me are do you need more of the problem thank-you David
Could be a thermostat problem... cheap to fix.

HOWEVER (loaded) there are several things that could go wrong to duplicate the issue as you describe it.

Try wiring in a new digital thermostat first, but if that does not fix the problem, be prepared to call a HVAC Tech.

Don Kelly

The next time it refuses to work, take wires off tstat, the red should go to r/c and the white goes to w on tstat,, if this is correct,, just twist the 2 wires together,, this will bypass your tstat,, if it works OK,, you need to replace the tstat,, if furnace doesn`t work as normal you will have something wrong with furnace,, I hate to see people buy parts guessing that it might be broke,, and then if it was wrong,, they are out the money(waisted),, this is all providing you have a furnace and not a heat pump