Pressure Leaks are the most common cause of the error code C983 on newer model Midmark M11 autoclaves (M11-020 thru -022 with Serial # prefixes RS, RT, RV & V).

But what exactly is a Pressure Leak?

A pressure leak is any leak of steam, air or water within the autoclave. Here are the four most common causes:

A faulty Door or Dam Gasket

If you can see steam coming out anywhere around the door, the door or dam gasket is the cause and they both should be replaced

Midmark recommends replacing both gaskets at least every 12 months. Find the High quality M11 Door & Dam Gaskets by Clicking Here

A faulty Air Valve

A properly functioning Air Valve removes air from the chamber. When it senses air, it opens and allows air from the chamber to pass through to the Water Reservoir

When it senses steam, it closes and seals the chamber. When the Air Valve is defective on the Midmark M11 Autoclave, it either will not close, or will not open, or opens to soon.

A faulty Vent Valve

The Vent Valve is designed to open at the end of the cycle, allowing the steam to enter the condensation coil inside the Water Reservoir

Once the steam travels through the coil, it is cooled down enough to return the from a gaseous state, back into the liquid state (water)

A faulty Fill Valve

The fill valve opens at the beginning of the cycle when the display reads “FILLING,” and then shuts off and seals when water touches the Water Level Sensor located inside, and to the rear of the chamber

While a problem with the Door & Dam Gasket is obvious and easy to see, finding a leaking valve will require a little more investigation, but is not difficult.

The first thing you will need to do is remove the left side panel (as you are facing the autoclave (the side where you put the water in). You can find the instructions for removing the panel by Clicking Here.

Once the panel is removed, you will see the two reservoirs, the larger reservoir is the one you are interested in. On top of the reservoir is a lid. Remove the lid by sliding it to the rear and get it out of the way.

Inside the reservoir, you will see the condensation coil. There is a hook on the end of the reservoir that sticks out above the water line. The end of that hook is one of the places you are going to be watching (a dental mirror can come in handy here). The other place is the bottom of the reservoir

Now, start a cycle and when the temperature gets ~240 degrees

First, look for bubbling coming from the bottom of the reservoir. If you see bubbles, then the fill valve is defective and needs to be replaced.

If you do not see bubbles, then start watching the end of the hook on the coil

You are looking for steam or water to be coming out of the coil. If you see steam coming out, then the air valve is defective and needs to be replaced. But, if you see water, then the vent valve is defective and needs to be replaced

Once you have found the pressure leak and replaced the defective part(s)on your Midmark autoclave, the error code should go away and the operation returned to normal