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<h2 id="isPasted"><u>Introduction</u></h2><p>The &quot;F9&quot; error code indicates AC undervoltage and overvoltage protection. This article is for <a href="https://www.pioneerminisplit.com/collections/vertex-ducted-central-split" target="_blank" rel="noopener noreferrer">Vertex Ducted Central Split (DYC-18) systems</a>.&#xA0;</p><p><strong>Cause:&#xA0;</strong>There is an AC power supply voltage problem.&#xA0;</p><h2 id="troubleshooting-diagram"><u>Troubleshooting Diagram<img src="https://attachments.gorgias.help/Q9r0k7BYaV2vg13y/hc/9JWjXVxG8m6DvMqm/2026020218-17cf8889-013d-48e1-bbba-75a15c672415-dyc18_troubleshooting_f9.png" style="width: 800px;" class="fr-fic fr-dib fr-bordered"></u></h2><h2 id="troubleshooting-notes"><u>Troubleshooting Notes</u></h2><ul><li>Use a multimeter to measure the power supply voltage and confirm the voltage is normal. Abnormal voltage is lower than 172V or higher than 275V.<img src="https://attachments.gorgias.help/Q9r0k7BYaV2vg13y/hc/9JWjXVxG8m6DvMqm/2026020218-70aa0ba8-e479-4340-ae7f-81fce8dc515b-dyc18_troubleshooting_f9_multimeter.png" style="width: 300px;" class="fr-fic fr-dib fr-bordered"></li><li>If the power supply voltage is normal, replace the main board.&#xA0;</li></ul>

The "F9" error code indicates AC undervoltage and overvoltage protection. This article is for Vertex Ducted Central Split (DYC-18) systems.

F9 Error Code

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By Error Code

Error Codes for Vertex Ducted Central Split (DYC-18) Systems

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F9 Error CodeUpdated 4 days ago

Introduction

Troubleshooting Diagram

Troubleshooting Notes