I need to change my Aprilaire 700 from *automatic* to *manual

Is this a newly installed unit it sounds as if there's a wiring issue. Could you show a picture of the wiring terminals. If this is not a new install try turning of your furnace fan.

Sorry to read about your problem, I hope this helps you out.
did you hit the reset

Digital Humidifier Control (Model 700): (Automatic or Manual mode) Check system operation and reset Change Water Panel indicator by setting the knob to "Test/Reset". With HVAC blower operating and HVAC calling for heat, humidifier will operate for one minute. DO NOT LEAVE IN TEST MODE AS HUMIDIFIER WILL NOT OPERATE.

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It appears your Aprilaire model 700 is wired to only operate when your HVAC fan is operated by your thermostat. Your HVAC installer can wire the humidifier control to operate the humidifier during a heat call, fan call or to turn on the fan when there is a need for humidification. Please contact your HVAC installer to have them change the wiring.

Thank you for giving us the opportunity to be of service
Sincerely,

Brad Uselmann
Technical Support
Research Products Corporation
www.aprilaire.com

Hi max temp is 140f 60 c

Based on the information that I have found changing the humidifier from a manual setting to an automatic setting is somewhat easy. It will require you to remove the little blue resistor that is located at the humidistat on the two screws labeled odt and replace that with an outdoor temperature sensor part 8052 that needs to be ran to the outside of the home. Depending on your technical abilities you may be able to perform this procedure, but may need to get a contactor involved.

You have a faulty humidistat

Greg Sunsetmech

Humidity must be hi enough in the house or Humidistat is not working. Do you any way to check humidity in the house?
If the Humidistat is set as Automatic, try to leave it as Manual.

connect two wires at humidifier without any wirng connected if works problem is in wiring or humidistat

i believe e3 is an outdoor sensor problem, most people use manual mode, you should see a blue jumper that is connected to 2 OD terminals at the control, or if u use a sensor there should be a wire run outdoors, if you dont have the manual mode part you have to get it from an aprilaire dealer, cant just jump it out, it is a resistor

the solinid may be stuck or the humistat is wired wrong