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DP
Treadmill

Model # 21-3900A Official DP treadmill

Here are the diagrams and repair parts for Official DP 21-3900A treadmill, as well as links to manuals and error code tables, if available.

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Model diagram and schematic

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Showing 10 of 73 parts  |
5/16 Locknut 25009800
#54

Motor and walking belt assembly diagram

5/16 locknut

Part #25009800

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

Lock Nut 25001500
#53

Control panel diagram

Lock nut

Part #25001500

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

Motor Pan 09146800
#26

Motor and walking belt assembly diagram

Motor pan

Part #09146800

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

Bolt 22011500
#44

Control panel diagram

Bolt

Part #22011500

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

Motor Mount 38338610
#27

Motor and walking belt assembly diagram

Motor mount

Part #38338610

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

Wr Harns/pot 39344100
#11C

Control panel diagram

Wr harns/pot

Part #39344100

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

Bellows 09104600
#8

Control panel diagram

Bellows

Part #09104600

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

Washer 26000667
Washer

Part #26000667

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

Treadmill Drive Belt 09091000
#14

Motor and walking belt assembly diagram

Treadmill drive belt

Part #09091000

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

Handrail 30446116
#9A

Motor and walking belt assembly diagram

Handrail

Part #30446116

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

Symptoms for treadmills

Choose a symptom to see related treadmill repairs.

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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

Effective articles & videos to help repair your fitness & exercise

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

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Top questions about Sears and Sears PartsDirect

Top questions about Sears and Sears PartsDirect

Get answers to frequently asked questions about Sears and Sears PartsDirect.…

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