Question 1

Red LED constant glow

Accepted Answer

Possible cause: The inverter is switched on.. Normal operation. No action required.

Question 2

Red LED quick flashing

Accepted Answer

Possible cause: The inverter is switched on by positive battery voltage.. Check the 12V supply line, inspect the plug fuse, and ensure connections are secure. If the issue remains unresolved, contact an authorised service agent.

Question 3

Red LED slow flashing

Accepted Answer

Possible cause: The inverter is switched off by positive battery voltage.. Check the control line signal and wiring connections. If repairs or internal diagnostics are required, have repairs carried out by a specialist.

Error Code / Indicator	Symptom / Meaning	Step-by-Step DIY Fix	Suggested Actions
`N/A`	Red LED constant glow Possible Cause: The inverter is switched on.	Normal operation. No action required.	DIY Safe
`N/A`	Red LED quick flashing Possible Cause: The inverter is switched on by positive battery voltage.	Check the 12V supply line, inspect the plug fuse, and ensure connections are secure. If the issue remains unresolved, contact an authorised service agent.	DIY Check / Tech Fallback
`N/A`	Red LED slow flashing Possible Cause: The inverter is switched off by positive battery voltage.	Check the control line signal and wiring connections. If repairs or internal diagnostics are required, have repairs carried out by a specialist.	DIY Check / Tech Fallback

Dometic MCR9

Technical Specifications

Master Troubleshooting & Diagnostics Matrix