I have a aprilaire 112. How do you test the solenoid valve to determine if it working properly?

Hello, I like to apply voltage directly to the solenoid valve to see if is working. Just take the two wires from transformer and connect to solenoid valve, if the valve clicks and water starts flowing the valve is good

May be an issue with the solenoid valve. check for voltage at the valve. if there are error codes check the owners manual for cause. I am providing a link to the manual if you don't already have one. the last thing to check would be the control itself. the control and the solenoid valve are the 2 main items for the unit. hope this helps.
http://www.aprilaire.com/themes/aa/en/manuals/AA-Humidifier-Owners.pdf

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1. No click at the solenoid valve indicates an electrical problem. Contact your heating and air conditioning dealer to further check the electrical components of your Aprilaire Humidifier.

1. The click sound at the solenoid valve indicates there is electricity to the solenoid valve. By turning the dial of your humidifier control to a setting above the “click point” you should see water coming out of the drain line within a few minutes which would indicate your humidifier is working.

1. If the solenoid valve makes a click sound and there is no water draining from the unit, this would indicate the flow of water is being obstructed.

1. To determine if water flow is being obstructed, turn the dial of your humidifier control to the off position. The first location you would want to check for an obstruction would be at the saddle valve located on the water line supplying water to the humidifier. When checking the saddle valve, you want to make sure it is completely open. This can be done by turning the valve all the way to the left. If anything is clogged, it can be dislodged by turning the saddle valve all the way to the right and back to the left. Once this is done, turn the humidifier control dial above the click point and you should see water coming out the drain line.


If water is still not coming out of the drain, check the orifice and in-line strainer to make sure they are not clogged. The orifice is located in the tube on the discharge side of the solenoid valve and the in-line strainer is located on the inlet side of the solenoid valve. You may clear the orifice by inserting a needle through the small opening. Clean the strainer by running it under warm water to dislodge deposits or replace. After clearing and re-installing the orifice and strainer (be sure to double wrench all water connections), turn the humidifier control dial above the click point and you should see water coming out the drain line.

Most likely you have crud buildup in the solenoid valve. But first make sure that you test accross the solenoid connections for voltage when the furnace is OFF. Put your meter to AC volts and see if you see 24 Volts when furnace is ON and 0 Volts when furnace is OFF. If you get those readings then you need to replace your solenoid valve.
Available from mfg for about $55-60
or on ebay for about $40 shipped.
search for Aprilaire 4040 Solenoid

If the above tests fail, you will need to ensure that the wiring is correct and not shorted, but is probably your valve. Install a fridge water filter in the water line to help prevent this in the future.

if it works in the test mode then it should be okay but you can get a humidity gauge from radio shack and set in the house to see how high or low its is. the humidifier is only going to give a max of 45% humidity

There is a small oriface that is installed next to the solenoid valve. It sounds like this oriface is missing. It reduces the water flow through the humidifier when it is working properly. You should be able to disassemble the solenoid fittings to check and see if the oriface is in the water line. For a "temporary" fix regulate the water pressure down by closing down on the saddle valve.
Good luck
HVAC Teacher

Disconnect the two yellow wires. The water should stop. If it does you have a bad (or miswired) humidistat. If the water does not stop the solenoid valve is bad. These valves are known to be expensive. You might want to consider replacing the whole unit.
Good luck
HVAC Teacher

if humidifier was wired into thermostat circuit for power instead of seperate transformer , this can happen. you need to see if you voltage going to the solenoid valve. if you do , and it isn't opening, the valve is bad . this is assuming that it is using a # 50 relay to come on only when the fan runs . . make sure the water valve is open

You need to determine whether the problem is in the solenoid or in the furnace electronics. You could put a voltmeter on the solenoid connection to see if the furnace is still holding the solenoid open after the blower stops. This will tell you whether it is the solenoid or not.

Kurt, a couple of things you can check. First when you turn the humidistat do you hear a click from the solenoid? This would indicate that you are in fact getting power. Check the saddle valve from the supply. Turn it in and out to make sure it is not clogged. You should have a inline strainer on the inlet side of the valve. Make sure it is not clogged with deposits. On the discharge side of the valve should be an oriface, make sure that is clog free. If you have an meter you can check for power at the soleniod or pull the harness off and ohm it. Should show continuity. Catriver...post back.