During the run, the temperature on the A200 controller drops 10°C or more and then recovers. The heat light remains OFF when the temperature drops. Why does this happen?

The instrument is experiencing a pressure fault. There are three possible reasons for this fault.

(1) More than 2 L of solution was in the vessel during the digestion process.

A pressure fault will most commonly occur if there is more than 2 L of solution in the vessel during the digestion process, leaving a small head space. Never use more than 2 L of solution in the vessel during the digestion process.

(2) Metal parts within the vessel are experiencing corrosion.

If the solution level is below 2 L and the instrument is running acid detergent, it is possible that corrosion of metal inside the vessel is producing additional gas that increases the pressure inside the vessel. Check for corrosion in the following areas:

• Inside the wall of the vessel
• Agitator disk in the bottom of the vessel
• Metal parts of the bag suspender (including the weight)

Corroded parts must be replaced.

(3) The pressure switch has failed.

If you are not using more than 2 L of solution and the metal parts in your vessel are not corroded, replace the pressure switch. Refer to A200 Service Procedure Pressure Switch Replacement (FS010) for instructions.