I have Carrier Weather Maker Gas Furnace; Does not start, Thermostate have only 9 volts... I checked the thermostate connected to the board and found 9 volts between Red and ground.
I guess it is the transformer...but it is very hard to remove to check as it is under the Board...any one can help...How to remove the board..as well check the Transformer for 24 volts...or how to proceed.
With the thermostat in the off mode, check the voltage between red and white or red and yellow. You should get about 24v. 9 is a little strange. Usually the transformer is not the culprit. Possibly a wiring issue or a board issue, but it's hard to say with just two paragraphs.
If you think the problem is the transformer, go to the control board on the furnace. You should find two tabs labled sec1 & sec2 (door switch closed). Check the voltage there. Is it still 9v? If so, remove the wires, and re-check the voltage Still 9v? Check the incoming voltage are you getting about 120v? If so, then I would suspect the transformer.