Aprilaire 550 not working...please help

Three weeks ago my gas furnace stopped working, I checked but couldn't find the problem so I called the plumber in. This guy did a lousy job and just wanted to make more money and I didn't let him do it (change fan timer control board) and problem turned out to be blown fuse on the board. I only paid for his diagnostic work. Also, he did pull one wire of my Aprilaire 550 humifier wire from the transformer. This humidifier was working last year. I connected the wire back for the humidifier but I still didn't get humifier to work. What is the voltage (24 V) going into the humidifier's solenoid ? I tested the circuit using a 50-1000 V voltage tester and didn't see wire getting power.

Any idea where the problem might be ? Can it be the humidistat (humidifier controller) bad ? Transformer bad ?

 

It works now.

 

It's 24 volts..


What did you find wrong??

 

Basically, I connected the misplaced wire and that was all needed. When I tested the humidifier for working, I didn't leave the heat on too long. I also expected the water returned back to humidifier drain pipe too soon and thought that humidifier not working.

I was using the wrong voltage tester as indicated in previous email. I used the 50-1000 V tester to test the 24V and getting nothing of course. I later bought a 0-250 V tester and sure enough I got something.