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Discussion Starter · #1 ·
I need to replace a circuit board in an Aprilaire 800 humidifier.
My unit has 2 circuit boards.
The top one is the one that needs replacing.
Any tips for this replacement?

Thanks for any help or advice!
 

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How did you come to conclusion the board needs replacing?

If you are certain the board is out, do you know what went out on the board and how do you know?

Price out the parts you need online, how much for your needed parts total?

From my search on Amazon same unit is $675 on Amazon, so maybe there are some used ones you can file on local sales sites, Offerup, facebook marketplace, letitgo, varage sale.
 

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Discussion Starter · #3 ·
Hi, Championpatriot!
I chatted with the folks at Aprilaire.
They diagnosed the issue as the upper circuit board.
I’ve already purchased a new board. About $130.

FWIW, I had a solid red ‘Fill’ light condition.
Replaced the canister first.
Problem was still there.
There is a water level sensor in the canister.
And a wire that goes from this circuit board to that sensor.
I’d say its highly likely this circuit board is the source of the problem.
 

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Thats not too bad! $130 better than a few hundred huh! Glad to hear it worked out on that front.

If by chance once you pull off the old circuit board look underneath at all the soldering and see if any of them have air gaps, I had myself an issue with my furnace not firing gas. Once I pulled the board off there small fractures on a couple of the pins, I soldered it up and I was back in business! I sent the new control board back I had purchased in case I could not fix it!

Have a good one.
 

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Discussion Starter · #5 ·
Replacing the top circuit board is fairly simple.
Aprilaire recommends replacing the canister each year and the electrode wires every three years.
I replaced all of those with this change.
Here goes:

1. Turn off Power at switch/circuit breaker.
2. Remove electrode wires from canister top.
3. Remove water level sensor wire from top of sensor.
4. Loosen clamp for steam hose and pull hose off canister.
5. Lift canister straight up and remove.
6. Route three wires through hole and over to the circuit board side.
7. Disconnect electrode wires from lower circuit board.
8. Disconnect black wire that goes from top board to lower board.
9. Snip off plastic connectors on circuit board from the canister side and pull board out.
10. This is a good time to do any other cleanup. Like cleaning the sediment from the drain port.
Replace the o-ring in the drain port. Check the steam hose, etc.
11. Install the new plastic clips on the new board.
12. Push the new board into the frame.
13. Connect the new electrode wires to the lower board.
14. Thread one electrode wire though the sensor loop in the upper board.
15. Thread both electrode wires and the new yellow water level sensor through the hole to the canister side.
16. Connect the black wire between the upper and lower circuit boards.
17. Install the new canister.
18. Connect the two electrode wires and the water level sensor wire to the canister.
19. Push the steam hose onto the canister and tighten the hose clamp.
 
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