Chromagen Error E4 — Collector Sensor Fault

What Does This Error Mean?

Error E4 means the collector temperature sensor (the probe on the solar panel on the roof) has failed or is reading an impossible value. The controller cannot tell how hot the panels are, so it stops the pump as a safety measure.

Affected Models

Chromagen CR Series
Chromagen Optima
Chromagen Crown
Chromagen Prisma

Common Causes

Collector sensor (T2 or TS2) failed or broken
Sensor cable damaged by UV, heat, or physical wear on the roof
Connector at the controller corroded or loose
Sensor reading outside acceptable range due to extreme roof temperature

How to Fix It

Note whether E4 is constant or intermittent.

If E4 appears briefly then clears, the cable may have a loose connection that expands with temperature. If it is constant, the sensor itself has failed.
Power-cycle the controller.

Switch off the system at the wall for 60 seconds and restore power. If E4 returns within minutes, the sensor is confirmed faulty — do not keep cycling.
Check the cable at the controller end.

If the sensor cable is accessible where it enters the controller box, inspect the connector for corrosion or a loose pin. Note what you see for the technician but do not attempt repairs yourself.
Book a technician.

The collector sensor (T2) sits on or in the solar panel on the roof. Replacement involves accessing the roof, removing the sensor, and routing a new cable to the controller.

When to Call a Professional

Yes — the collector sensor is on the roof and involves the solar circuit. A Chromagen-authorised technician or solar plumber is needed to replace it safely.

Frequently Asked Questions

Can the system heat at all while E4 is showing?

No — the controller uses the collector sensor to know when the panels are hotter than the tank. Without it, the pump stays off and no solar heating occurs. The backup electric boost may still work.

How long does an E4 repair take?

Usually 1–2 hours for a technician. The sensor cable replacement is straightforward once the technician is on the roof. It is a standard service job.