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Compatible models
R40403-001
R40403-002
20054502
ST9120A
ST9120B
ST9120C
Replaces：R40403-001, R40403-002, R40403-003, 20054501, ST9120C 2010, 1138-83-1002A, 87H88, R20054502, R38493B001, 87H8801. 1138-100, 1711, HCSI PLC=0, 164322, T9AV5D12-22, 16391, CPC E 94V0, 1138-83-1003A
Operating Line Voltage: 85 to 135 VAC, 50/60Hz.
Secondary Control Voltage: 18.0 to 30.0 VAC, 50/60Hz.
Maximum Blower Loading: 15FLA, 30LRA, 120 VAC; 7.5FLA, 15LRA, 240 VAC.
Maximum Inducer Loading: 3FLA, 10LRA, 120 VAC; 1.5FLA, 5LRA, 240 VAC.
Humidifier Terminal: .8A, 115 VAC. Electronic Air Cleaner: .8A, 115 VAC.
walt
August 22, 2025
My fan was just coming on randomly. Even when the system was off.Simple board replacement solved the problem.
JEFFREY
July 16, 2025
It was prefect match fit right on, no issues.
James Love
June 5, 2025
This is not a OEM branded product, but nearly identical placement of circuits of the ST9120* I replaced. The lack of the LED in the corner is the only thing that sets it apart when the cover is on. This board has 3 dip switches instead of 2 for fan on/off delays. You can figure out what to do with them from the included documentation. Also the 5 amp fuse is replaceable on this card instead of soldered to the board. I can't speak for the life time, but the quality of components and craftsmanship is comparable to the OEM. Worked out of the box. It is 1/3 the cost of the name branded ST9120U (universal replacement) and probably doesn't have as many features, but if you are working on a 20 year old unit, you don't need those extra features. If it dies early, I will update the review, but so far easy, economical, and out of the box drop in solution.
Brynn Johnson
June 2, 2025
The circuit board stopped working after a short period. It didn’t fix the issue with my furnace and caused more problems. Poor quality.
Do not feel like cotton
March 22, 2025
I bought this to replace my old Honeywell circuit board, and it has been perfect.The wiring was the exact same, so i just swapped the wires from my old circuit board to this new one, and my family is chillin again in 73 degrees. easy instructions!
Darius
February 28, 2025
The circuit board malfunctioned almost immediately. It was supposed to be a direct replacement, but it caused more issues than it fixed. Very unreliable.
Cmarius
December 29, 2024
I started out my career as an electronics technician and worked on thousands of circuit boards. This furnace board is very simple, having only 3 relays (all rated correctly) and two logic chips. I measured the spade terminals at 1/4" as required. There are three resistors that look different from the OEM - and with color bands that are hard to decipher, and so I did an Ohm check, they were spot-on. This is a drop-in replacement for the OEM with all pins, terminations, labeling and mounting identical to the OEM. The instructions are written in proper English, see sample. The wiring diagrams are a bit fuzzy but legible, and the board comes packed in a static-resistant zip closure bag. I would not hesitate to install this board in place of the OEM.
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