How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask BillyHvac Your Own Question
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22109
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Type Your HVAC Question Here...
BillyHvac is online now
A new question is answered every 9 seconds

I have an aprilaire 600, red light on controller flashes

Customer Question

i have an aprilaire 600, red light on controller flashes continuously and coincides with a clicking sound from the controller. Manual temp resistor reads 44K, voltage is 27v. dont know why it clicks continuously when its on any setting except off
Submitted: 11 months ago.
Category: HVAC
Expert:  BillyHvac replied 11 months ago.


I apologize for the delay. I just logged on and saw that no one had picked up your question yet.

Do you still need assistance?

Customer: replied 11 months ago.
I do
Expert:  BillyHvac replied 11 months ago.

do you have wired in series with a pressure or sail switch?

Customer: replied 11 months ago.
the humidifier has been installed and in use for 10 years and none of the wiring has changed over that time period. it just recently started the clicking sound from the controller and it occurs when the Red LED flashes on the controller board.
Expert:  BillyHvac replied 11 months ago.

I understand that...and all parts have been there for 10 years. But I need to know what you have for control as the humidistat is only one part. Many units have an air switch in the same what I need to know is once the wires leave the humidifier do they go to humidistat and then something else?...or ONLY furnace humidifier and humidistat?

Customer: replied 11 months ago.
all wires come out of the furnace in one jacketed cable and run directly to the controller except the Red wire. That wire is split out of the bundle and is spliced to the solenoid that allows the water to flow into the humidifier. so the Red wire is broken and the solenoid is wired in to the Red wire circuit. I have not look inside the furnace to see where those wires are attached.
Expert:  BillyHvac replied 11 months ago.

Thank you, ***** ***** things!

Now all we need to know is if inside the furnace...the red wire runs from:

a transformer attached to HUM terminal

a current sense relay wrapped around a blower wire

or direct from a HUM terminal on circuit board

Then we should be close to wrapping up.

Customer: replied 11 months ago.
here is the wiring that is in place
Wires coming from the furnace: Red and White wires are connected to a solenoid of some kind and dead end there. Its a brown plastic box about 3" x 1" x 1". The other end of the red wire goes to the water solenoid and then to the controller board. The white wire runs directly to the controller board
The blue and yellow wires come out of the dead man switch in the furnace, to a small transformer and then to the controller board in the humidifier to connections labeled R and C.
Expert:  BillyHvac replied 10 months ago.

thank you.

Now first..check the transformer wires that go from transformer to board and the blue and yellow that feed the transformer. Make sure all are tight and secure.

Then the brown plastic box....can you see any numbers on it or post a pic of it?....this is something in the series we need to check

Customer: replied 10 months ago.
wires are tight, here is a picture of the box, its very hard to read the info on it though.
Expert:  BillyHvac replied 10 months ago.

Thank you!,,,that is a current sensing relay. It allows 24v to humidistat only when the blower is running.

Now as a test...remove the 2 wires that go to the yellows...and attach the 2 wires direct as though the current sense relay is not there.

Customer: replied 10 months ago.
i removed the current sense relay from the circuit by connecting the white and red wires together that go to the two yellows and it made no difference. the Red light on the controller board still continuously flashes and the clicking sound is still there as well. other ideas?
Expert:  BillyHvac replied 10 months ago.

remove the wires that feed from the transformer.

temp place on the furnace terminals R and C

Customer: replied 10 months ago.
out of town for a few days, will check when i get back later this week.
Expert:  BillyHvac replied 10 months ago.

keep me posted when you return

Customer: replied 10 months ago.
i looked at the furnace controller board and could not find any terminals labeled R and C. That is what you wanted me to do, correct? To take the wires off of the transformer and connect them directly to the furnace controller board.
Customer: replied 10 months ago.
attached is a picture of the furnace controller board
Expert:  BillyHvac replied 10 months ago.

ok yours are separated and labeled prob different.

R is 24v on left side of board with red wire. Then you see the light blue wires from left bottom of transformer..those are "c' or "common".

But you are a wire from transformer red bottom right and transformer common bottom left blue wires and apply direct to solenoid

Customer: replied 10 months ago.
i connected directly , bypassing the xformer, and ensured that the terminals on the furnace board had 24v. when connecting directly to the Humidifier board the same red light flashing and clicking noise was there. There was not change to the original issue.
Expert:  BillyHvac replied 10 months ago.

thank you. are the wires you hooking direct to the 2 wires coming out of the solenoid?

Customer: replied 10 months ago.
the water solinoid? No, i bypassed the transformer in the furnace and took the blue and yellow wires from it and connected them to the 24V and ground ( red and blue wires) on the furnace control board. they then run to the humidifer board.
Customer: replied 9 months ago.
no, they were not. i bypassed the xformer and connected the two wires from go from the Humidifier control board( yellow and blue) to the 24V on the furnace control board. I dont think the solenoid is the issue as when I set the humidifier to run it will do that and water goes to the pad but the load clicking noise is present.

Related HVAC Questions