No water flowing through humidifier, solenoid hot to touch.

The water flow through the humidifier is limited/controlled by an orifice. This small opening can easily clog. After disassembly use a small wire to clear the debris trapped in the small hole,

Hope this helps?

I have a General Aire humidifier on my furnace. I was having the same issue with vibration noise. I took the solenoid off and took it apart. There is a part that had a screen and a very small hole. I cleaned all the parts in my ultrasonic cleaner. The I reassembled the solenoid. It had an electromagnet that was held on by one nut. I reinstalled the solenoid mechanism and started the system. I had way better water flow, but still some vibration. I tightened the nut holding the solenoid and electromagnet together and the vibration stopped.

Try removing the cover, and manually cycling on the controler switch? Does the solenoid click on, next to the humidifier (the unit with the water line running through it, with wires coming out of it)? If it does click on, is water running down the water pad? It doesn't necessarily drain water when it's working correctly. All of the water SHOULD be getting evaporated into the air return duct.

If it's clicking on, but no water is running out, you should check the water supply saddle valve and make sure it wasn't turned off during servicing.

If it's not clicking on, you should test that you are getting voltage (12v-18v DC) to the solenoid. If you're not, check all wiring connections and make sure they're tight. If you still don't get power, you have either a problem with your control unit/humidistat, your DC power supply, or the control board on your furnace. You may need to call a HVAC technician at that point, depending on your comfort level/skill level in that regard.

When you say the solenoid "stays hot" do you mean it's physically hot to the touch? Hotter than the water lines running into it?

If the solenoid is getting hot, it probably has a bad coil, and if you continue to operate it, you will probably burn up your DC power supply.

If you're getting voltage, you have water pressure, and the solenoid is still not opening, replace the solenoid.

Most humidifiers have a strainer on the inlet side of the solenoid valve, if this strainer is clogged up it will reduce the water flow to the humidifer. Usually sediment builds up in the strainer and all you need to do is remove it and clean it up and reinstall it.

http://www.appliancefactoryparts.com/humidifiers/helpcenter/breakdowns/honeywell/honeywell-he360a1027.html
A breakdown diagram of parts etc above.
http://www.appliancefactoryparts.com/content/pdfs/110672-4.pdf
Shows you the HE360A.
To me it sounds like it is wired incorrectly, the solenoid should NOT get too hot at all. The PDF above shows wiring data.

Valves do go bad, but I had the same issue and it was the inlet orifice that was plugged.
To fix: Turn off the water supply. Disconnect the water inlet line to the solenoid. The water inlet line connect to ~ 1" long piece that goes into the solenoid. Unscrew the water inlet piece and remove it from the solenoid. Check it for water flow - water should slowly drip out the small orifice at the soleniod side. There is a pin-hole sized orifice on the solenoid side and it doesn't take much to plug it. There is also a narrow cone-shaped filter inside the inlet piece. You can use tweezers to remove the filter and & use a safety pin or sewing needle to clear the orifice. Check the filter, clean it if necessary, and reinstall the filter. Now check for water flow thru the part before reinstalling. Reconnect the water inlet line and turn on the water supply. Turn your humidistat to trigger the humidifier. You should see water flowing through the drain tube.

In order of probability:
1) (incorrect wiring) Make sure that humidistat is in SERIES wired with the furnace.
2) (shorted wires) Check that two wires to humidistat are not touching...use your glasses if you need them!
3) (bad humidistat) disconnect the humidistat and put an ohmmeter accoss the two terminals when it is turned on you should read 0 ohms, and when off it should read infinate ohms, if not pass both these tests, you need new humidistat.
That is it, there are no other possibilites!

the humidistat on this unit just acts as a set of dry contacts. with the humidifier plugged in, you should be able to touch the 2 brown wires by the water solenoid together and get the power fan to run and the water solenoid to enrgize. if you do this and water does not flow, you most likely have a bad water soenoid. it is either electrically bad, or just plugged with water deposits. sometimes you can pull it apart and clean it, sometimes you just have to replace the solenoid.

solenoid valves dont just burn up just like that you have a recurring restriction due to bad water.Check the saddle valve at the water heater first then check for postive water flow at inlet to the solenoid valve,if you have water flow the valve is clogged with sediment.

I installed this humidifier (and had a lot of trouble installing it!) and was surprised by the flow of water. Mine leaks out of the bottom of the unit so I haven't actually used it yet. I'll try to figure out why it's leaking this weekend. I thought there would be less water flowing through the pad. I suspect that the weight of the unit is causing it to not be plumb so some water is dripping off of the pad and past the drain tray.