Tenant just reported that the heating system is not working. Over a 3 or 4 day period the system was working sporadically. Original issue was that the furnace would kick on, the blower start, and heat the house. Over a period the room would reach temp but the blower would stay on and continue to blow cold air. (the fan is set to auto). This has happened before and was usually fixed by shutting down the system allowing it to reset itself.

Now - the unit is not working at all. Using the thermostat, I have tried to turn the fan to the "on" position - nothing. I've tried to set the thermostat to "cool" - the A/C will not even kick on. Its like there is no juice going to the unit.

The main power is on, the circuit board checked, kill switch checked and I am at a total loss as to why the unit seems to be dead.

Could it be a thermostat issue? How can I bypass the thermostat to see if the furnace itself has power?

Can anyone think of anything else?

First does your furnace have an LED that you can see down in the blower compartment? If you do it should give you a flashing light code to tell you what the problem might be.

Second on the circuit board you should have a 3amp or 5 amp fuse somewhere on the board, it is shaped the same as the small square shaped card fuses. Pull it and see if it is blown, if so you will have to find the reason for it blowing before you replace it. This fuse only controls the control voltage, "the low voltage 24 volts" If you have moved wires around on the furnace or on the thermostat it is possible that you may have shorted across a couple of wires.

Third you can short across the red and the green wire in the thermostat, this should make the blower run. There is also a test terminal somewhere on the circuit board. Read the instructions on how to make the test. First the assist exhaust fan should come on then the hot surface ignitor should get hot, next the gas valve would open but it won't for safety reasons, next the blower motor will start and run for a minute or so. If one does not do what is is suppose to do that is the problem.

I got the same problem... I did change my new t-stat... everything seemed OK... also make sure limit switch and roll out...