Offered for sale is this Chamberlain Garage Door Operator Internal Limit Switch Assembly, Part Number 41D3452, New.  This limit switch assembly has been used on most Sears Craftsman 139.53000 series operators, as well as Monark, Master Mechanic, Wayne-Dalton, Raynor, Chamberlain, Liftmaster operators. 

    A symptom of a worn limit switch assembly is inconsistent operator travel.  The operator will not be consistent in how far it either opens or closes the garage door.  Adjusting the external travel limit knobs will often have no effect.  Inspect the limit switch - if the center plastic "traveler" contacts can be gently rocked back and forth, then that slop can translate into the door having inconsistent travel inches at a time.  Replacing the limit switch assembly can bring back an exactness to the door travel, as long as there are no other issues with either the door or the operator.

    If you have an older, early '80's operator where the limit switch assembly is ALL white and the RPM sensor is also mounted to the limit switch assembly then this ASSEMBLY will NOT work.  The "traveler" can be snapped out of this assembly and reinstalled into the all-WHITE assembly, but the results may not be satisfactory.

    I can't address whether or not this switch assembly will work in any particular model - if it looks like the one inside your operator then it will work.

    If you have any questions please use the "Ask Seller A Question" forum.  Please read  my terms before making a purchase.