LiftMaster 8500 problem - cable tension?

[danb35]

I've been having some trouble lately with my 4-month-old LiftMaster 8500. Intermittently, it will fail to close the door all the way, reversing at some point. That point is typically early in its travel, but can be as much as 2/3 of the way closed.

When the failure occurs, the overhead light flashes 9 times. To be clear--the light is on, it turns off then on rapidly nine times, then off, then on steady. The manual says that this indicates that the cable tension monitor has been triggered.

I'm able to watch the monitor device as the door opens and closes, and the cable tension remains pretty steady--I don't see the monitor arm moving back and forth at all. The way it's installed, the arm would need to move at least 1/2" to trip the microswitch in the monitor base.

I detached the cable tension monitor wires from the opener and checked for continuity--it measured an open circuit. When I tripped the microswitch inside the monitor, the resistance didn't change.

Am I right in thinking I have either a defective cable tension monitor, or damaged wiring to the monitor? Or should I be looking elsewhere?

 

[buddyboy]

the door won't work unless that monitor is plugged in... correct?

if so it probably shouldn't read open circuit when you checked continuity

 

[Chevy-SS]

I installed two of those last year on my new garage doors. Mine are very sensitive and react quickly if something gets in the way.

Is it possible you have something causing an obstruction, or perhaps just binding a little? For a quick test, simply disconnect the opener and then operate the door manually. Of course, it should be butter smooth and relatively easy to open and close.

 

[Trey T]

I have the same problem with my previous chain drive and the 3800 (older model of 8500). There's nothing wrong with my opener, it's the garage door; it doesn't close smoothly.

 

[MikeF]

Lift master is funky, some safeties are a normally open circuit and reverse when the circuit is closed. Others are reverse.

 

[MikeF]

Switch might be touchy or have some internal.damage,

 

[frank001]

I've been having some trouble lately with my 4-month-old LiftMaster 8500. Intermittently, it will fail to close the door all the way, reversing at some point. That point is typically early in its travel, but can be as much as 2/3 of the way closed.

When the failure occurs, the overhead light flashes 9 times. To be clear--the light is on, it turns off then on rapidly nine times, then off, then on steady. The manual says that this indicates that the cable tension monitor has been triggered.

I'm able to watch the monitor device as the door opens and closes, and the cable tension remains pretty steady--I don't see the monitor arm moving back and forth at all. The way it's installed, the arm would need to move at least 1/2" to trip the microswitch in the monitor base.

I detached the cable tension monitor wires from the opener and checked for continuity--it measured an open circuit. When I tripped the microswitch inside the monitor, the resistance didn't change.

Am I right in thinking I have either a defective cable tension monitor, or damaged wiring to the monitor? Or should I be looking elsewhere?

I have three 8500s. On one door it would often trip the cable sensor when the door the was closing at the bottom, causing the door to open again.

After numerious times trying to adjust it, I finally took a piece of stiff wire about 10" long, hooked it over the plastic arm that touches the cable and hooked the other end to the door rail, holding the arm away from the sensor. Problem solved.





http://www.garagejournal.com/forum/s...light=frank001

 

[MikeF]

Until the door binds and the cable sacks and pops off the drum. They make a product we call "cable keepers" the bottom roller slips through the coil and acts as a spring, then the part about 6-8 inches long with the hook snaps.over the cables.and keeps em taught. If you bypass the sensor, it install those as a back up.

 

[frank001]

Until the door binds and the cable sacks and pops off the drum. They make a product we call "cable keepers" the bottom roller slips through the coil and acts as a spring, then the part about 6-8 inches long with the hook snaps.over the cables.and keeps em taught. If you bypass the sensor, it install those as a back up.

I've been using as I described for several months without a problem, so I suspect it's OK as is.





http://www.garagejournal.com/forum/s...light=frank001