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.