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I have a miller gas furnace model MMHA-056ABHR-01. Furnace not running, will not even start. Replaced t-stat and still will not start. checked power to unit - power is on fan will run if you turn on fan switch. dont know if it is the control module or what any ideas?

thanks, rb

Is your furnace switch a rocker type switch with 3 positions, ON, OFF, FAN? If so, check to see if there is 24 volts coming out of the transformer. OR are you turn the fan ON at the thermostat?

fan will not start from the tstat, only at the rocker switch, after replaceing tstat the furnace still will not start. no pilot, gas valve not opening and fan does not come on

Okay put furnace switch to off. Disconnect all the thermostat wires at the furnace. Connect red and white thermostat wires from furnace together. Turn furnace switch to ON. Furnace should start a cycle. If not, check to see if you have 24 volts coming from transformer. If you do not have 24 volts from transformer replace it. If you do have 24 volts from transformer problem is in either the wiring to the thermostat or the thermostat itself. Just for a test, hang a heat only thermostat from a nail with about 15-20 feet of thermostat wire connecting it to the furnace. Test run it like that for a while.

TRYED ALL THAT REPLACE TRANSFORMER, BY PASSED TSTAT, AND TRYED ANOTHER TSTAT. NO RESPONSE. GAS VALVE DOES NOT OPEN, IGNITER DOES NOT COME ON. DOES NOT GO INTO CYCLE, WHAT NEXT????????

Does your combustion motor start? If not kill power to the furnace, look at small black motor on lower right side of unit. You can see small fan fins through the motor vents. Take a small screwdriver and turn those fins. They should move easily. There are times once you move that motor it will start up.

That motor has to start first before anything else will happen.

History on furnace, last year my dad started the furnace and it reached temp but would not shut down so he tried to turn off furnace at tstat, that did not shut it down. Furnace kept running and heating so he finally went to the breaker and shut down the power. When he went to start this year nothing would run. I tried several times to turn the combustion motor and it turned fine, was not froze up and spun ok, but furnace would not start. Next????? Thank you for all your patience!

If the unit was in full burn when he shut it down a limit switch may be out. Check all your limit switches. First look at them to see if they are resettable. There will be a little button right between the terminals. If you see one push it down hard. If not manual reset, pull them and test with a continuity tester, they should be closed, if open replace it/them.