Aprilair model 760 does not go on

Some helpful videos in the link as well as text articles and a link to a previously answered question on Fixya.

https://www.google.com/search?q=Aprilaire+760+making+strange+sound

It may be too high a water pressure for the solenoid.

Aprilaire Humidifier, too powerful a solenoid? Vent ducts noise.

https://www.houzz.com > discussions > aprilaire-humidifie...
The noise might be caused by having the water pressure up too high for the solenoid. Try backing off the water supply until the sound goes away. Hopefully, ...
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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.

the solenoid allows water to flow to jet that then runs down the pad the solenoid is control by the stat

A simple check you can perform on your aprilaire 760 is the following:
1) locate the two brown wires coming out of the 760 (these wires will be wired to tell the 760 to turn on when the hvac bower is on and the humidistat is calling for moisture).
2) temprarily disconnect the two brown wires from the external wiring and then short the wires together. All you're doing here is bypassing the your thermostat and bower-on indicator.

With the 70 unit plugged in to the wall outlet and the two brown wires connected together, both the fan and the solenoid valve (water inlet valve) should both be activated.

If you have 24 volts to the solenoid, then it's not the control card. It's either the solenoid or there's an orifice in the water line at the solenoid that sometimes stops up. To check the solenoid you need to disconnect the power to the system and disconnect the solenoid wires (the two brown wires) and ohm the solenoid. If you get a low ohm reading around 50 ohms or then the solenoid is good and you need to check the orifice. If the ohm meter doesn't move when you ohm across both leads then it's the solenoid and it needs replaced.

Yes, just check to see if you have 24 volts going into the solenoid. If you do and it is not opening its probably bad. Since you verified the water lines, filter, orifice and saddle valves are not obstructed. Change the solenoid valve. When you price the part. (it's not cheap) consider paying about 30% more and just change the whole unit.
Good luk
HVAC Teacher

The tune up kit that I ordered arrived on Friday and I installed most of it on Friday night. While it is nice to have a new frame and the distribution panel and I think the price of the whole kit was fair considering it comes with the parts and 2 water panels, the fix was really simple.

The kit came with the water distribution tube with with a new blue orifice (Aprilaire #4232) already inserted. This orifice is in the end of the plastic tube at the solenoid end. When I removed the old water distribution tube, the old orifice was not really dark blue anymore but kind of a light blue and was deteriorating from 12 years of exposure to the chemicals in the water. What should have been a pin-hole size opening in the orifice was up to about 2mm or a little more so the orifice was letting way too much water through.

If anyone else has this leaking problem, and your orifice is several years old, I would check that first. It is a $2.75 part and may be the cause of the leak. The whole feed tube kit is only $8.75 and includes the feed tube, nozzle, orifice, ferule, compression nut, strainer so if you need to replace the orifice, I would order the whole feed tube kit for a little bit more.

Hope this helps,
Roger...

What type of plumbing do you have? Galvanized, copper or pvc?

It could be that the humidistat is not calling for humidity. Make sure that you have the dial turned up all the way (as far as it will go, just to test it) and that the blower on the furnace is running - if the unit is properly wired, the water will not run unless the blower on the furnace is running. This should do the trick. If not, the only other thing would be a bad humidistat. Good Luck!

Sounds to me like the solenoid valve is your problem and it is likely stuck due to sediment. I beleive Aprilaire has superceeded all of their old valves to the part number 4040 (used on all models of aprilaire humidifiers) - anyone who services these units regularly likely has one in stock usually $60 - 100.