Dehumidifier will not run; display shows E1 shortly after power-on.

Safety first: Unplug the dehumidifier from the mains before removing any covers. Do not work on the unit while it is connected to power.

Steps to check and fix:

• Power-cycle the unit: Unplug for 5 minutes, then plug back in and try again. If E1 returns, continue.
• Access the control panel: Remove the front grille or top cover (on most Challenge dehumidifiers, a few screws along the back and sides hold the cover). Carefully lift the control panel.
• Locate the ambient temperature sensor: It is usually a small probe or bullet-shaped NTC sensor clipped near the air inlet grille, with two thin wires going to the main PCB.
• Inspect wiring and connector: Check for broken, pinched, or chewed wires. Reseat the connector on the main PCB by unplugging and plugging it back in.
• Test the sensor (if you have a multimeter): At room temperature (~20–25°C), the NTC should show a resistance typically between 5–20 kΩ (exact value varies by model but should not be 0 Ω or infinite). If it reads open circuit or short, the sensor is faulty.
• Replace the sensor if defective: Order a compatible Challenge ambient temperature sensor (NTC) for your model. Disconnect the old sensor from the harness clips, route the new sensor along the same path, and connect it to the PCB.
• Reassemble and test: Refit the covers, plug the unit back in, and power on. The E1 code should clear automatically if the sensor is working.

When to stop: If the sensor and wiring are intact but E1 persists, the main control PCB may be faulty and should be diagnosed or replaced by a qualified technician.