This most commonly means the thermostat is missing ac power. The furnace is not sending power to the thermostat. What is make/model of furnace?
I am not at home now and will have to check.
Ok...here is a test.
Remove thermostat from top wall mount plate. You will see thermostat wires attached to lettered terminals. Locate R and G......then use a paper clip shaped in a U...touch one end to R while touching other end to G. If the fan/blower starts, it is a thermostat issue. If the blower does not start, it is the furnace not sending power to thermostat.
A blown fuse on the circuit board in the furnace, a high water safety switch and main power to furnace off are the biggest culprits.
Have you checked the small fuse on the circuit board? It is located in the blower section.
If you can get me the model number of the furnace I can be more specific.
Also are you running heat or air? If in ac use...there can be a blocked drain switch that shuts power off to thermostat.
Get me the model and we can move forward.
Thank you...also if you can get the model number of which Criterion...it will start with a RG...then other numbers. Then I can you specifically where to check. There various models and that number will give us direction.
It is Model RGDG-12EARJR
I have removed the lower panel cover and cover on the circuit board and can't find a fuse. The humidifier is dry; dusty and cruddy but dry.
Thank you...in the RGDG the fuse is in the wire that leads from the transformer to the circuit board. It is an inch long and a small tube inside a capsule. Also, tape door safety switch down and see if the circuit board blinks a sequence of lights.
the biggest culprit is outdoor thermostat wire to ac unit damaged......check that wire before turning power back on...or do not hook up Y and C on circuit board.
I replaced the fuse without really expending a lot of energy in looking for the reason for it. I guess I'm hoping it was an isolated incident; like a lightening strike or something during the summer months while it was not being used. It was very difficult to find a replacement for the fuse. None of the vendors I checked with had the right size, voltage and amperage combination. I ended up replacing the fuse holder with one that fit the 250V 2A requirement and used an off the shelf size from radio shack. Thank you for your help. The furnace was still working this morning, so whatever caused the fuse to blow has not been repeated (so far). I did buy spare fuses, just in case.
You did the correct thing....replace with fuse and holder readily available.
I appreciate the cooperation and competent help......well done