I have three zones of forced air/baseboard heating in my house. I had the furnace shut off for the summer and after turning it back on, two zones in the house work and one does not. Any tips on how to troubleshoot the problem? The simplest problem (my guess) it could be (other than gas pipes being shut off) is the thermostat is working properly. Is there anyway to bypass the thermostat to see if that is the issue. Re: gas pipes being shut off, I have checked that and all seem to be on/flowing.