My MAX-HD4 reports a temperature of 500C.
It’s running normally and is cool to the touch. Tried different firmware versions, no change.
Are you running anything on PoE on the HD4?
I remember something about PoE on the HD4 possibly leading to incorrect temperature values been created.
If its cool to touch then it should be ok!
Iv’e had units reporting 70ºC and be very warm to touch that still functioned (not that I like to run the equipment that hot!)
It’s connected to a Poe switch, but no, POE is not enabled on any ports.
I’m not concerned because obviously now we don’t have a working temperature sensor. This could be a concern because it’s in a closed rack in a mobile environment. Also, you know, for the price, it should work 
Hello @Vincent_Royer,
If the unit is still in warranty, then we recommend creating a support ticket, you will need to download the diagnostic file from the Status page of the router and add it to the report, you can also in the report reference this chat and then when you receive your ticket number, post the ticket number here.
We have had this happen on a unit of equipment too recently, the unit needed to go back to Peplink to be resolved.
Happy to Help,
Marcus 