Liftmaster 8500 installation question

[zhang]

Finally want to pull the trigger to get 8500. I was reading the installation manual last night. The only concern I have is about the chain tension monitor. The manual requires 3/4 inch of clearance from the wall. Mine only have about 1/2 inch to the wall. Besides not using this feature, does anyone have idea to somehow make it work?

Thanks

 

[bimmer1980]

There was a thread on here earlier about the Liftmaster and how to by pass the cable tensioner with a resistor. Do a search and you can probably find it....

 

[zhang]

Thanks for the quick reply. Bypassing it is easy. I was thinking of make it work with the close distance from the wall. Or I am now thinking if I could use the port to have some other safety feature.

 

[dave*99]

Can you remove some drywall at the mounting location or otherwise recess the tension monitor?
It is there to prevent the opener from unwinding the cable. If the cable unwinds, the door could drop fast and hard.

 

[zhang]

Thanks Dave. I will try that. Or I will use the 1K ohm trick others mentioned.

 

[pattenp]

My cable is only 1/2 inch off the wall at the closed position. As the drum steps down the cable distance from the wall increases as the door opens. Just make sure when you mount the sensor that it is pulled out enough that the contact is not pushed in. You can figure out the resistor size needed by using a multimeter to test the resistance across the sensors wires with the sensor in its pulled open position.

 

[djjsr]

I suggest you DO NOT try to eliminate the cable tension monitor. You may regret it.

Some guys have problems with the tension switch because there's a little slack in the cable when the door starts down and it trips the switch. Sometimes, raising the back of the tracks a little may help. But the best fix is installing a pair of bumper springs. They mount on the track and compress against the top of the door when the door is fully open. This keeps a little tension on the cables when the door starts down. Cheap and easy fix.

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