Synology NAS Error Code 39: How to Fix It

Q: What temperature triggers Error Code 39 on a Synology NAS?

Synology Error Code 39 is triggered when the internal system temperature approaches a threshold that could cause hardware damage — typically around 70°C (158°F) or above depending on the model. The NAS will automatically shut down to prevent permanent damage if the temperature is not reduced quickly.

Q: Will my data be lost if my Synology NAS shuts down due to Error Code 39?

A thermal shutdown itself does not erase your data, but if the shutdown occurs while files are being written to the drives, those files can become corrupted. Drives that overheat repeatedly can also suffer physical degradation over time. This is why backing up data immediately when you see Error Code 39 is the most important first step.

Q: How do I check my Synology NAS fan speed and temperature in DSM?

Log in to DSM and go to Control Panel > Hardware & Power. The 'Thermal' tab shows current system and drive temperatures. The 'Fan Speed Control' tab shows the current fan mode and lets you switch to Full Speed Mode for maximum cooling. You can also install the 'Resource Monitor' package from Package Center for more detailed real-time monitoring.

Q: Can I replace the cooling fan in my Synology NAS myself?

Yes, on most Synology models the cooling fan is accessible after removing the outer casing and is secured with standard screws. You will need to match the replacement fan's size (commonly 80mm or 92mm), voltage (typically 12V DC), and connector type (usually a 3-pin or 4-pin connector). Always power down and unplug the NAS completely before attempting a fan replacement.

Q: How can I prevent Synology NAS Error Code 39 from happening again?

To prevent future thermal shutdowns: clean dust from vents and fans every 3–6 months, ensure the NAS is in a well-ventilated location with several inches of clearance on all sides, keep the room temperature below 35°C (95°F), set up DSM temperature alert notifications, keep DSM firmware up to date, and periodically verify fan operation through the Hardware & Power settings in DSM.

Abstract

Synology NAS Error Code 39 is a critical thermal warning that means your device's internal temperature has reached a dangerous level and an automatic shutdown is about to occur to protect the hardware. This is typically caused by blocked airflow, failed cooling fans, a dusty environment, or a malfunctioning temperature sensor. Immediate action is required — if the NAS shuts down unexpectedly during a write operation, you risk data corruption or drive failure.