Humidifier won't turn on with furnace fan set to Auto.

Humidifier receives voltage when the indoor blower motor comes on in the heating mode, and blower motor dose not come on right away.See if water flows when indoor fan is blowing heat, Good luck.

Hope this helps, check and see if humidistat is set to 35% humidity and that bypass damper on humidifier is in the open position or winter position.(humidistat is usually located on cold air return duct near furnace). Next, replace humidifier media pad, remember to replace media pad (filter) annually, you also may want to clean any lime deposit out of humidifier housing with a solution of warm water and white vinegar before installing your new media filter.Remember to turn power off at side of furnace when cleaning humidifier and replacing media. Before installing new media turn power back on to furnace, set humidistat to the on position, turn furnace thermostat above room temp., and inspect humidifier to see if water is running from top,(you may want to have a bucket under humidifier when checking for water), if you see water running, turn power back off to furnace, properly install new media filter, reconnect humidifier cover & set humidistat to 35%. If you do not see water present, check water supply valve to humidifier and make sure its turned on. If water supply valve is open, then check water supply tubing for blockage.And the last things to check is to make sure all registers through out your home are open and not blocked by any objects, also make sure furnace filter is cleaned, if none of this works refer to installation manual to see if humidifier was sized and installed properly, Good luck.

Is the furnace fan set on auto or on. You will get better humidity if you keep the fan on. It won't add much to your electric bill because many of the newer furnaces operate the fan on DC voltage. Try it!

The furnace should be equipped with a #50 relay to turn the Humidifier on and off when only when the furnace blower is on. You should have a test mode on your humidistat. Do you have water coming up to the solenoid valve? Make sure that the saddle valve is turned on to supply the water to the humidifier. Is your humidistat set high enough to turn the humidifier on? Is it plugged in?
Good luch
HVAC Teacher

Hi!!! You might have a bad flame sensor its a single rod located in the burners its white..If the unit runs and then shuts off and on and off.change your flame sensor..Good luckk..

It sounds like the humidifier may be improperly wired.
It's hard to solve without checking the wiring, but it seems like the humidistat is wired so that as the dial is advanced, it incorrectly turns on the fan, or furnace, or both.  The contacts of the humidistat should be wired so that they turn on the solenoid only.  Also, the power to the humidistat, to turn on the solenoid, should come on only when the fan is on.
Hope this helps!

ther might be dip swiches on the circuit board you might have to change

This may not be a solution, but a couple things you might want to look at. First, the humidifier may not be big enough for your house - just because a contractor installed it doesn't mean he sized it right. Second, humidity may only be 30% locally by the humidistat, but higher in other parts of the house - it depends where the humidistat is located. Finally, look at your hot water line - I'm surprised he ran it off hot water and not cold - seems like a waste of energy to me, but the feed line may be clogged by sediment from the water heater

J-

I had this problem several years ago. In order for the water to flow, the outside temperature sending unit must indicate to the controller that it is less than 60F. If not, the unit will not operate outside of test mode. Check the temp outside where your sending unit is (could the sun be heating that side of the house?) and ensure that the circuit to the sending unit is working. I had a bad wire splice inside a wire nut stopping the circuit. Took me a long while to figure it out.

If the outside temp and your sending unit circuit is ok, I wish you luck on your troubleshooting.

adx_98

I would guess from the info provided that you only have two wires going to your thermostat which would explain why the fan switch doesn't work on the thermostat. You can bypass the thermostat as a first step in troubleshooting. After that it depends on the type of furnace, standing pilot or electronic ignition...