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DP
Treadmill

Model # 21-3900 Official DP treadmill

Here are the diagrams and repair parts for Official DP 21-3900 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 76 parts  |
Lock Nut 25001500
#51

Figure 1 diagram

Lock nut

Part #25001500

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

5/16 Locknut 25009800
5/16 locknut

Part #25009800

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

Long Key 29353400
#27D

Figure 2 diagram

Long key

Part #29353400

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

On/off Switch 37030800
#11F

Figure 1 diagram

On/off switch

Part #37030800

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

Ear Clip 37023700
#4

Figure 1 diagram

Ear clip

Part #37023700

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

Screw Sm 20018800
#35

Figure 2 diagram

Screw sm

Part #20018800

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

Bushing 37016900
#6D

Figure 1 diagram

Bushing

Part #37016900

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

Wire Harns A 39312300
#11K

Figure 1 diagram

Wire harns a

Part #39312300

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

Bushing 29098500
Bushing

Part #29098500

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

Front Leg 38334916
#16

Figure 2 diagram

Front leg

Part #38334916

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 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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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 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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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 walking belt

How to replace a treadmill walking belt

A worn walking belt will begin to slow down during use. If your treadmill walking belt is worn out, replace it using the…

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Repair difficulty
Time required
 45 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

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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