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Aprilaire
Humidifier

Model # 550 Official Aprilaire humidifier

Here are the diagrams and repair parts for Official Aprilaire 550 humidifier, as well as links to manuals and error code tables, if available.

There are a couple of ways to find the part or diagram you need:

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  • In the search box below, enter all or part of the part number or the part’s name.

Not all parts are shown on the diagrams—those parts are labeled NI, for “not illustrated”.

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Owner’s manual

Model diagram and schematic

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ALL PARTS
Showing 10 of 24 parts  |
Transformer 4010
#14

Model 550 diagram

Transformer

Part #4010

The manufacturer no longer makes this part, and there's no substitute part

Valve Sadd 4001
#18

Model 550 diagram

Valve sadd

Part #4001

The manufacturer no longer makes this part, and there's no substitute part

Wick Pad 10
#1

Model 550 diagram

Wick pad

Part #10

The manufacturer no longer makes this part, and there's no substitute part

Adptr-vlv 4229

#NI

All parts diagram

Adptr-vlv

Part #4229

The manufacturer no longer makes this part, and there's no substitute part

Cover Latch Spring 4225
#17

Model 550 diagram

Cover latch spring

Part #4225

The manufacturer no longer makes this part, and there's no substitute part

Panel 4221
#6

Model 550 diagram

Panel

Part #4221

The manufacturer no longer makes this part, and there's no substitute part

Panel 4220
#5

Model 550 diagram

Panel

Part #4220

The manufacturer no longer makes this part, and there's no substitute part

Orifice 4231
#12

Model 550 diagram

Orifice

Part #4231

The manufacturer no longer makes this part, and there's no substitute part

Feed Tube With Compression Sleeve 4226
#19

Model 550 diagram

Feed tube with compression sleeve

Part #4226

The manufacturer no longer makes this part, and there's no substitute part

Stainer 4004
#10

Model 550 diagram

Stainer

Part #4004

The manufacturer no longer makes this part, and there's no substitute part

Symptoms for treadmills

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Why does my treadmill's walking belt slow down?

Main causes: damaged walking belt, improper belt tension, lack of belt lubricant, bad drive motor...

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Why is my treadmill's walking belt slipping?

Main causes: damaged walking belt, improper belt tension, bad roller bearing...

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Why is my treadmill's walking belt off center?

Main causes: rear roller out of alignment, damaged walking belt, bad roller...

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Why won't my treadmill start even though the console display works?

Main causes: missing safety key, bad control console, wiring failure, faulty motor control board, bad drive motor...

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Why is my treadmill's heart rate sensor not accurate?

Main causes: faulty sensors, wiring failure, bad control console...

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Why does my treadmill have no display?

Main causes: bad control console, wiring failure, bad motor control board...

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Why won't my treadmill power up?

Main causes: no power, bad power cord, tripped or faulty overload switch, bad power switch, wiring failure, bad motor co...

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Repair guides for treadmills

These step-by-step repair guides will help you safely fix what’s broken on your treadmill.

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How to replace a treadmill motor controller

How to replace a treadmill motor controller

Your treadmill motor won't run with a defective motor controller. Replace the motor controller if it doesn't operate the...

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Repair difficulty
Time required
15 minutes or less
How to replace a treadmill drive motor

How to replace a treadmill drive motor

A defective drive motor won't run when activated by the motor controller. Replace the treadmill drive motor if it doesn'...

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Repair difficulty
Time required
15 minutes or less
How to replace a treadmill walking board

How to replace a treadmill walking board

A worn-out walking board creates friction with the walking belt and causes the belt to slow down during use. Replace the...

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Repair difficulty
Time required
30 minutes or less

Articles and videos for treadmills

Use the advice and tips in these articles and videos to get the most out of your treadmill.

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How to enjoy all the online benefits we offer on our Sears PartsDirect website

Learn about all the convenient features on our Sears PartsDirect website that make your parts purchases easier....

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How to use a multimeter to test electrical parts video

How to use a multimeter to test electrical parts video

Learn how to use a multimeter to check for wiring problems in an appliance that's not working...

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