Furnace humidifier keeps running

[czgunner]

Our furnace humidifier solenoid valve started hammering the other night. It seems water pressure was pushing it open.
I installed the new solenoid today and turned the water pressure way down.
The water is running even with the fan off. This is a DC solenoid, so polarity shouldn't be an issue.
I don't remember the water running all the time before, but I could be mistaken.
Honeywell HE240A2001 on our gas furnace. Humidistat (sp?) is only set to 20% and it's actually quite warm for January in WY (40%) ambient in the house right now.
Any ideas?

 

[PCustoms]

Solenoid is controlled by something....

What's that circuit doing?

 

[czgunner]

Solenoid is controlled by something....

What's that circuit doing?

Yeah, I just pulled it apart and it has the DC in and the humidistat wired in series. Thanks.
The fix will be using the fan to control the circuit, right? I am not sure how to make that work. Isn't the fan power AC?

 

[The Cobbler]

you sure about DC voltage?. Controls for furnaces & humidifiers are usually AC voltage

 

[czgunner]

you sure about DC voltage?. Controls for furnaces & humidifiers are usually AC voltage

I'm pretty sure its DC. Big AC adapter plugged into the wall providing power for the solenoid.

 

[chinboys]

I'm pretty sure its DC. Big AC adapter plugged into the wall providing power for the solenoid.

Perhaps the AC adapter is a step down transformer which steps down the 120V AC to 24V AC. Confirm it with an AC voltmeter.
If so, this voltage is driving the water valve solenoid to an open position thus your problem.

 

[PoorUB]

you sure about DC voltage?. Controls for furnaces & humidifiers are usually AC voltage

I'm pretty sure its DC. Big AC adapter plugged into the wall providing power for the solenoid.

Look at the old valve, it will say 24VAC or 24VDC right on the valve. Some Honeywell models used a DC solenoid, but I don't remember which ones.