The selector switch (knob) on the Waters Positive Pressure-96 Processor (186006961) turns freely, past the minimum and maximum flow settings - WKB227357

SYMPTOMS

• Selector switch (knob) seems broken, turns freely, even past the minimum and maximum flow settings

ENVIRONMENT

• Sample preparation
• Solid-phase extraction (SPE)
• Waters Positive Pressure-96 Processor

CAUSE

Loose nut on selector switch (inside unit) 

FIX or WORKAROUND

1. Remove the rubber feet on the bottom of the unit with a 1/8-inch hex key.
2. Remove the bottom panel.
3. Locate the selector switch’s nut (inside unit).
4. Position the selector switch with the dowel pin facing up, in the middle position.
5. Tighten the selector switch nut (inside unit). 
   • Hand-tighten the nut, and use pliers to tighten just a bit more.
6. Reinstall the bottom panel and feet.

ADDITIONAL INFORMATION

This procedure should fix the problem.

Here are examples of the selector switch comparing normal and abnormal (past minimum and past maximum) for reference:

Normal:                                                        Problematic - Past Min:                                    Problematic - Past Max:

User Manual:

• Waters Positive Pressure-96 Processor Operator’s Guide (186006961) (lit code 715002662EN)