Versions Compared


  • This line was added.
  • This line was removed.
  • Formatting was changed.

Table of Contents


Honeywell HE280C2010/U Higher Capacity Whole House Bypass Humidifier


Humidifier Pad - HC26A

Fix - No Water Flow

A some point the solenoid failed. I think the original solenoid is garbage so I will replace with something a bit more robust. 

Controller Images


Here is the schematic that I put together based on some testing.

You would think that the GND pin on the 555 would go to ground via a pullup and that would be that.

Other thoughts:

  • D2 is a zener diode which acts as a voltage regulator for the 555 chip.

555 Timer Reference Diagram

Fixing the Solenoid

Since the solenoid was no longer activating, it seemed like a replacing it was in order. The replacement solenoid that I purchased was rated 24 VDC but didn't activate when connected. Perhaps the transistor Q1 does support the amount of current required by the new solenoid. 

I opted to bypass the 555 timer circuitry by connecting pin 4 of the internal connector (under cap) to ground. The 555 timer is not required. 

New Parts

 Baomain 1/4 Inch Brass Electric Solenoid Valve for Air Water Valve N/C (Normally Closed) DC 24V$22.00 CAN

Generic Pneumatic Push in Quick Touch to Connect Fitting 1/4" OD Tube x 1/4" Male NPT 90 Deg Swivel Elbow Coupler.

I would have bought straight ones but couldn't find them for a good price.

$13.00 CAN for 5

Finish Product

Here is a picture of the finished fix. Should be more maintainable now that these changes have been made. The new solenoid valve will allow a lot of water to pass so I have ball valve (not shown) limiting the flow to a trickle.

Future Updates

  • Replace solenoid output connector with barbed connector