My furnace cut out about a year ago. The hvac guy i used told me the gas valve was no good and that the flu was partially blocked. I cleaned out the flu, he replaced the gas valve ($700+) and it worked great for a year. Today the furnace does not fire up. Pilot is working. I cleaned out the flu (there was definitely quite a bit of debris, so that was probably the cause for the shut off) .... The flu is now clear, but when i turn the system back on the thermostat calls for heat, but there is no gas flow to the burner... could the valve have failed that quick, or should i be looking at something else like the CO sensor or something... just looking for some direction before shelling out another 700 bucks... Thanks in advance for any ideas or assistance....
I was wondering why the flue is clogged? I've never had to clean mine. Well anyway, I use a shop vac to vacuum out any dust or rust that accumulates on the gas valve on the rare occasions it failed to work,and that fixed it every time.
There are a few possibilities. The valve runs on a low voltage line. The low voltage is provided by a transformer. It it possible the transformer is bad. Be sure the power switch to the furnace is on. (should be on the side of the furnace. Easy way to check is (on the thermostat) turn the fan switch from auto to run. The blower fan should come on. Check that the gas valve is in the ON position.(if you have had to light the pilot it may still be in pilot position.) Another possibility is a clogged gas line. If you have an older home rust can accumulate inside the iron gas lines. Where the gas line attaches to the furnace there should be a drip leg. This is a short length of pipe that points down with a cap on it from the TEE that goes into the furnace. This short piece of pipe is to catch any moisture or rust that comes thru the line. First TURN OFF the gas at the shut off in the pipe it's self. This is a quarter turn valve. When the handle is in line with the pipe the gas is on. When it is opposite the pipe (pointing out to the side) the gas is off. After turning the gas off, remove the cap from the bottom of the drip leg to remove any accumulation.USE PIPE DOPE not teflon tape when putting the cap back on.Turn the gas valve back on and check for leaks.
