99

REVERSED TACH FAULT

Otis · DSD 412 DC Elevator Drive

What does 99 mean?

The digital encoder signals and motor voltage signals do not agree in their indicated direction of rotation. This typically points to a reversal in the encoder's directional feedback wiring.

Common Causes

  • Encoder leads for direction (A and A/NOT) are reversed.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Reverse the connections for the encoder signals A and A/NOT.

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Verified technical data. Last updated: March 2026

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Source: Otis DSD 412 DC Elevator Drive