A new Aprilaire genuine replacement filter for the 600 model smelled so bad that we had to throw open windows to get fresh air into the house even though it's freezing outside. I called in a furnace repairman to check the system, but he found nothing wrong except the reeking filter, so he replaced it with another Aprilaire filter. Now the smell has greatly diminished, so I assume it will be gone within a day or two. Has anyone else had this problem with Aprilaire replacement filters recently?

I know of no answer to this except to remove the coating manually to prevent it clogging you filter.

Hope this helps, check and see if humidistat is set to 35% humidity and that bypass damper on humidifier is in the open position or winter position.(humidistat is usually located on cold air return duct near furnace). Next, replace humidifier media pad, remember to replace media pad (filter) annually, you also may want to clean any lime deposit out of humidifier housing with a solution of warm water and white vinegar before installing your new media filter.Remember to turn power off at side of furnace when cleaning humidifier and replacing media. Before installing new media turn power back on to furnace, set humidistat to the on position, turn furnace thermostat above room temp., and inspect humidifier to see if water is running from top,(you may want to have a bucket under humidifier when checking for water), if you see water running, turn power back off to furnace, properly install new media filter, reconnect humidifier cover & set humidistat to 35%. If you do not see water present, check water supply valve to humidifier and make sure its turned on. If water supply valve is open, then check water supply tubing for blockage.And the last things to check is to make sure all registers through out your home are open and not blocked by any objects, also make sure furnace filter is cleaned, if none of this works refer to installation manual to see if humidifier was sized and installed properly, Good luck.

sounds like you may have it wired to a continuous power source vs one that shuts off with the furnace. The most common wiring is red to C & white to W

you need to be using only genuine AA parts if you are the feed tube or try may be cracked AA sells an annual maitenance kit on thier site for about 60 bucks go to www.aprilaire.com

go for the Aprilaire 600 but make sure they install the outdoor sensor and set it up for AUTO operation

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

http://www.aprilaire.com/themes/aa/en/manuals/600a.pdf here's the link fo the manual. read page thirteen about the inline screen that the unit has. it may be clogged up.

No, it is not an accurate statement.

These units have simple configurations They have a water supply similar to a ice making referigerator, an enclosure connected to your supply duct that houses a prop fan and media, a seperate humidistat and a drain for excess water. Your unit may also include fancy controls including an outside thermometer & humidistat to avoid over humidification that can cause problems during freezing weather. The humidistat looks a lot like a thermostat and is located in your living space or in the return duct. The prop fan in the box pulls air from the duct, through evaporation media and back to the duct. An electric solenoid valve releases water that pours over the media.

If the humidiy is below the humidistat seting and the AC/heater is running, the Aprilaire fan starts and the solenoid valve opens. I suspect the facier controls include the flashing warning light.

The warning light spells problem. Aprilaire's customer service should be able to provide guidance for the homeowner in the form of simple checks. I suspect your contractor is avoiding a warentee call and the trip it requires.

A word of caution. These humidifiers can be powered directly from your air conditioning unit control board from an auxiliary connection. If the control board isn't rated to carry the current required by the Aprilaire fan, valve and controls or the Aprilaire encounters and electrical problem, the board can be damaged. This can be avoided by using a relay. The AC board switches a low energy relay. 120 volt house power is connected to load side of the relay and runs the Aprilaire.

My board cooked at a location near this connection, but I can't be sure that the load from the humidifier caused it since four of our neighbors also lost their board. It failed the evening of a snow storm and required a costly emergency after hours service call. The next day a new board required a three hour drive. Fortunately a fan powered propane heater kept our pipes from freezing.

Not happy either. I bought 3 Aprilaire 400 for my house (3 zones). I picked this style since I have attic installation and did not want to run drains. The first night I expected a major air quality improvement but no change in humidity. I have installed humidifiers before so I know the drastic improvement they make. So I watched for a season and still no humidity improvement. Absolutely nothing at all. Same exact observation as you all described. Only the bottom of the media was wet. I'm dissatisfied with Aprilaire 400. Do not buy! Since I installed humidifiers before and understand them I am converting the Aprilaire 400 to work like a Aprilaire 600. I simply unwired the float sensors, removed the floats/lid and using a knife cut some of the plastic cups so the water would drain well. I also cut open the plastic exit port some too so it wont clog from dust globs. I obviously added drains. HUGE RESULTS. On the very first cycle on the humidity in that zone went from 25 to 48. I am watching carefully. -GK

Modle 110 has a relay in it see if it is stuck.Hope this helps