What does McQuay fault code E4 mean?

Fault code E4 on McQuay systems indicates low pressure protection — check refrigerant charge. Check the McQuay installation manual for model-specific diagnostic procedures and recommended corrective actions.

How do I troubleshoot a McQuay system that won't start?

Start by checking power supply, thermostat settings, and safety switches. For McQuay equipment with digital controls, review the fault history log for recent error codes. Check that all safety interlocks are closed and the system is not in lockout mode.

Where can I get McQuay technical support?

McQuay technical support is available through their distributor network and online support portal. For instant AI-powered troubleshooting answers about McQuay equipment, try AskWhiz on WhatsApp — get expert responses in seconds.

HVAC

McQuay error codes, decoded.

Look up any McQuay fault code below. Each one is grounded in McQuay's own service documentation — the meaning, the symptoms, the causes, and the steps to clear it.

By Octavian Ghindea

Co-founder & CTO · Reviewed August 2026

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McQuay sits in our HVAC coverage. Every page here is transcribed from the manufacturer's manuals, not scraped from forums.

What error codes does McQuay display?

Tap a code for the full breakdown — meaning, symptoms, causes, and fix steps.

Low pressure protection — check refrigerant charge

Communication error — check signal cable connections

Outdoor unit sensor fault — check outdoor thermistor

Fan motor fault — check motor and capacitor

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Common questions about McQuay equipment

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