This article explains the possible causes and solutions to a Midmark M9-M11 New Style autoclave Error Code C646.

Midmark M9/M11 Error Code C646 Leave a comment

In this article, we’re going to explain one of the many error codes that can affect your Midmark M9/Midmark M11 autoclave. This article will focus specifically on error code C646. We’ll tell you about the problem, what displays when the error occurs, its possible causes, and the course of action to take to resolve said error.

However, if you’re more of a visual learner, we have a video on this error code available here.




Absolute pressure inside chamber is equal to or greater than 0.7 psig (5 kPag) for longer than 10 minutes. (i.e. Vent mode is not complete) 

Causes, Checks and Actions

Possible Cause 1: Chamber filter clogged. 
  • Check: Check if chamber filter is clogged. 
  • Action: Clean / Replace filter. (Clean with Speed-Clean and brush) 

M9 Mesh Vent Filter OEM available here

M11 Mesh Vent Filter OEM available here

Possible Cause 2: Air valve. 
  • Check: Leaking or defective air valve. Perform: Air Valve Test Check for excessive steam coming thru condensing coil spout.
  • Action: Clean/Replace air valve.

M9 Air Valve OEM available here

M11 Air Valve OEM available here

Possible Cause 3: Vent valve. 
  • Check 1: Inspect vent valve. (Clean valve, stretch spring) 
  • Check 2: With the sterilizer in the Vent Mode… Perform: Vent Valve Testing (The valve is normally open, and should not be energized during the Vent mode). 
  • Action: Clean / Replace vent valve. 

M9 Vent Valve Repair Kit OEM available here

M11 Vent Valve Repair Kit OEM available here

As always if you have any questions about this process or anything else please feel free to contact us and take advantage of our “FREE TECH SUPPORT.”

We also offer FREE VIRTUAL TECH SUPPORT to “See and Talk” with a “Real Time Live Technician” for any problems you may be in need of help with.

You can also use our “FREE MAINTENANCE PROGRAM”. Take the guesswork and worrying about what unit is due for maintenance and which maintenance cycle it is time for. We will keep track of all your autoclaves and let you know when it’s time for anything.

The Midmark M9 autoclave is available here. 

We also have the Midmark M11 autoclave here. 

Leave a Reply

Your email address will not be published. Required fields are marked *