I've got a Sears 1/2 HP garage door opener (model 139.53535SRT)that
I've installed back in March 1996. The double car wooden garage door
by itself (i.e. without garage door opener)works. Also, the garage
door opener when opening the garage door works. The problem is that
the trolley itself (without the garage door attached) goes down only
goes a few inches, then backs up and the white lights flash. There
are no obstacles in the way at the base of the garage door. The
little green light on the side panel also blinks 4 times although I
can't find what that means in neither the manual nor the inside cover.
I've lubricated the tracks for the garage door, the hinges, as well
as the chain. I also greased the T-rail as well as the gears (which
look fine) inside the unit and it still won't close. I've tried
increasing the down force to where it is nearly at maximum setting.
I've also checked the safety reversing sensor and both sides have
their green lights on to indicate that a connection from the beam is
good. Can anyone help with what the problem may be? Thanks in
If you pull the safety release on the trolley, will it go up and down
with out the trolley connected? Perhaps you have a bad gear inside
the unit that binds in one direction. Make sure the chain tension
is ok and not too loose or too tight. And that the chain is not
twisted where it connects to the trolley.
Most of the problems i have had with my sears is when one of the tension
springs break on the door.
email@example.com (Jay) wrote in message
If the opener moves exactly 4 inches then reverses it is most likely
the revolution counter board has gone bad or the revolution counter
"cup" as come unseated from the motor shaft (although it is possible
the main logic board is bad). The revolution counter board is the
small board that's beside the motor shaft. The cup w/ notches goes on
the end of the motor shaft & the logic board reads the timing pulses
that the counter board sends thru the notches in the cup. So when the
door hits something the timing of the pulses change & thus the opener
reverses. Therefore if they are not working properly the opener acts
as if the door has hit something.
If it is moving a different amount then 4" inches the suspect would be
the bearing where the chain sprocket shaft comes thru the motor head.
Once the bushing gets worn enough the shaft will bind in the bearing
and cause the opener to reverse. The bushing is an assembly that
includes the bushing, the mounting plate, the chain sprocket & shaft,
& the plastic worm gear. Remove the small limit sprocket on the end of
the shaft & the three screws that hold the plate to the motor head.
Remove the chain (make not of the chain & door position & re-install
in the same position) & lift the whole assembly out thru the top of
the motor head (may have to lower unit from ceiling for clearance).
From your description my 1st guess would be the revolution counter
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