Hyd. fan filter-by-pass test button

[Bob & Carol Howald`]

Does anyone know the procedure for using the Hyd fan filter by-pass
button located in the engine compartment of the coach (93pt 40). If I
push it in while the coach is idling it wants to stall the engine.??
All I can find in the book is to run the engine up to 2100rpm and
see if the red light come's on. This would indicate a filter problem's.
Nothing is said about the by-pass button. Thanks Bob 93pt Illinois