I have water flowing thru the selinoid, the supply hose is clear, the final fitting into the drip spout is clear, but there is almost no water coming out of it and into the 6 hole tray that drips into the evaproation pad. Thank you for your advice.

humidifiers have a drain and if there is water going in it will be coming out the drain. check drain to see if it is clear, check hoses going into top of humidifier for cracks, check filter in humidifier.

I would suggest that you locate supply valve to humidifier and loosen compression nut on outlet side to see if you have water at that point. If you do shut valve off and disconnect supply line on incoming water line and make sure it is clean. Check for plugged screens or lime build up. Clean as needed. If you aren't getting any flow thru shut off valve then turn off water supply to the valve and replace it. I hope this helps you. Thanks

If the water stops when the heater is not running then the humidifier is working fine. I know it seems like alot of water but that's how it's designed.

I have a HE220, HE 260 humidifier..by pass, flow thru. There is no water flow between the hot water tank and the humidifer. The water valve is on. Is there an inexpensive part I can replace myself first before calling a plumbing contractor?

Neither, even if the solenoid or humidistat stick, it should always drain properly. Is the unit mounted on the cold air return duct or the supply plenum? If it's mounted on the supply plenum, the water panel might be getting blown forward and spilling the water. High efficient furnaces also can leak water on the floor if its drain is restricted. If hum. is mounted on return duct make sure drain is clear by blowing through it. On Honeywell hum's I've seen the rubber hose from the solenoid valve to the distributor tray leak too, check the rubber 1/4" hose.

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.

No, it will not stop flowwing if it is the water supply. A solenoid valve opens the flow everytime there is a call for humidity, but it stops at the humidifier when there is no call, so it will leak from that point until it is fixed or tightened.

Check your plastic water orifice. It is in the hose fitting connected to the outlet tube of the water solenoid. It should be a blue one. Mine was completely eaten through, allowing full water flow, and thus overflowing the distribution tray. I replaced mine yesterday and no more water drips. May as well reflace the filter on the inlet tube of the solenoid at the same time. I used a piece of very stiff, but thin, wire formed into a small hook to remove both old parts. Replacements are readily available from multiple sources on line.

I corrected the problem...RH is rising nicely!! Installed by "professionals" on my Trane XV90....I redid their wiring and now have the following setup...

600A water supply coming from hot water line.
Removed orifice inside incoming feed tube.
control incoming water flow from saddlevalve on hot water supply ( make sure its a nice solid flow, no drips, but no "force" too it either)..enough to insure entire evaporator unit is wet and water is slightly flowing out of bottom to drain.

I also have it wired to run when ever the furnace blower is on. Heat or no heat. XV90 is variable speed, and by doing this the 600a is always adding moisture, until it reaches correct RH%

Also, I disconnected the outdoor temp sensor. I went to Radio Shack and bought a 47K ohm resistor ( 1/2 watt....4 pack for 99 cents). Installed that in place of outdoor sensor...now runs in manual mode. Have unit currently set to number 5.

Loosen the brass fitting where it connects to the soleniod valve. If water comes out your saddle valve is ok. Carefully retighten this fitting. With the humidifier turned on loosen the first fitting down stream from the valve see if water comes out. if it does turn the humidifier off and see if it stops, it should. That will tell you the the valve is ok then, just clean the filter and the oriface. if it does not turn on and off check the wiring. if ok replace the valve.
Good luck