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ErrorLib — Industrial Fault Code Library

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Hardware Preservation Fault

Hardware Preservation Fault (High Internal Temperature)

Allen-Bradley · Logix 5000 Controllers

What does Hardware Preservation Fault mean?

This fault is declared by the controller when internal module temperatures exceed a critical threshold, leading to a reset and immediate power disablement. The OK status indicator illuminates red, and the module remains unpowered until it cools below the Hardware Preservation Hysteresis limit. Subsequently, the module enters fault mode, logs the event, and displays 'CPU Temperature Fault' on the front panel. For 5580 controllers, this can be indicated by a flashing green OK status.

Common Causes

  • Internal module temperature exceeding the hardware preservation threshold
  • Inadequate cooling of the controller module

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Measure the ambient temperature within the control panel enclosure using a calibrated thermometer

  2. 2

    Visually inspect controller heatsinks and cooling vents for dust accumulation or obstructions

  3. 3

    Verify the operational status of any enclosure cooling fans or air conditioning units, confirming proper setpoints

  4. 4

    Check for proper airflow pathways around the controller module within the chassis/panel

Browse all codes in this manual (17)
Verified technical data. Last updated: April 2026

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Source: Allen-Bradley Logix 5000 Controllers
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