Precor Error Code 24 Reduce Speed Requested, Speed Not Reduced

Jan 08, 2022

Applies to

9.3X, 9.4x, 9.5x, TRM200-14, and TRM400-14 consumer treadmills

Issue symptoms

Error 24 only occurs on machines that use a DC drive motor. The error is triggered when the speed sensor detects that the speed is increasing when the motor current is decreasing. The following two possible causes could trigger an error code 24:

Possible Causes

Cause 1: Gravity assisted back drive condition

Gravity assisted back drive is probably the most likely cause for triggering error code 24.

Back drive is the additional backward drive applied to the running belt as the exercisers foot hits against the belt which momentarily increases the speed of the belt. However, under certain conditions the back drive can become excessive causing an over speed condition resulting in machine shut down.

Excessive back drive generally only occurs when the belt and deck are in new condition and the belt‑deck coefficient of friction is low. As the belt and deck wear, the coefficient of friction increases reducing the potential to cause an error 24 event. During a workout as the incline raises combined with the weight of the exerciser, the deck‑belt friction can be exceeded resulting in uncontrolled belt acceleration. The motor controller will detect the over speed condition and switch the treadmill power OFF. However, even with the power off, the weight of the exerciser could cause the belt to continue to accelerate. The exerciser must step off the belt to allow the running belt to slow and stop.

Cause 2: Failed LPCA

The LPCA DC motor current switching transistor has shorted providing maximum drive current to the motor. This failure will cause the drive motor and belt to start accelerating to maximum speed. The motor controller will detect the over speed condition and switch the treadmill power OFF.

Troubleshooting steps

Check for a failed LPCA

WARNING: Do not stand on the running belt during this test..

1. Stradle the running belt, do not stand on the running belt.
2. Switch the power ON. If the belt immediately starts to accelerate the LPCA has failed, replace the LPCA.

3. Start a manual workout. If the belt immediately starts to accelerate the LPCA has failed , replace the LPCA.

Check for a gravity assisted back drive issue.

4. Cycle the treadmill power.
5. Set the incline to the minimum level.
6. Go to the Error Log and verify that error 24 has been cleared.
7. Attempt to recreate an error 24 event.
   1. Step onto the belt and start a slow speed workout. Raise the incline to maximum attempting to cause an error 24 event.
   2. If no error 24 event, increase the speed to 5 mph (or higher) attempting to cause an error 24 event.
8. If there was an error 24 event, the belt‑deck coefficient of friction is too low to prevent an error 24 event. Continue to use the machine. As the machine use hours increase, the belt‑deck coefficient of friction will increase resulting in reducing the frequency of error 24 events to the point wherein the events will no longer occur.
9. If there was NOT an error 24 event, the belt‑deck coefficient of friction may be at a marginal level that only causes intermittent error 24 events. Continue to use the machine. As the machine use hours increase, the belt‑deck coefficient of friction will increase to the level wherein error 24 events will no longer occur.