Carrier Humidifier problem

[Hi]

I have a Carrier model 58WAV136-16 furnace. It has a humidifier attachment, and it seems that it is not sending any power to the solenoid that turns it on.

Does anyone know what conditions have to exist (that I haven't thought of) to flip the humidifier on? Things that I have thought of:

1. The fan has to be going
2. The humidistat needs to be set high enough to trip

Anything else? I opened the panel and checked the DC output of the humidifier port and there is nothing coming out of it.

Any ideas?

Thanks

[Dr. Hardcrab]

How does it know the fan is running? In other words, could it be using a current sensing relay that has gone bad?

[trader4]

Also, some can be wired so that they go on when the furnace burner is activated, instead of the blower. That's how mine is set up, which I think has the advantage that after the burner shuts off, the humidifier does too, so the remaing few minutes of blower time can dry out the media. Plus I don't have to worry about turning it off during cooling season.

[Dr. Hardcrab]

Damn! Nice idea. Never seen it done that way, but it makes sense!

[Bubba]

Thats how most of them work nowadays. Thats what the H or HUM terminal is for on most furnace circuit boards. Bubba

[Dr. Hardcrab]

Yeah. The terminals have been around for a while but I thought it just brought the humidifier on with the fan.