We just installed a Chamberlain whisper drive on our two stall garage. we want to install another one on the third stall. Can we operate both doors from the door control from the two stall?

You have to adjust the safety pressure sensor. It is set to too light a pressure. Check your manual for the adjustment.

Hi, Check that the rollers are free of obstruction. Check Battery is installed correctly in remote. Also check the codes are set correctly. Hope that helps.

You can find the user manual here Chamberlain Whisper Drive

If the wall button will operate the door up but none of the devices do then look at the wall button. Find the lock button and push it for 2 seconds and then try the remotes again. This is your vacation lock. You can get a manual at chamberlain.com. Now if the door does not open or close with the remotes you can reprogram them. Press the colored learn button on the motor head and then press the button on the remote. Repeat for each remote. If they fail to program you will need a new logic board. Thanks BB

Where the belt attaches to the trolley carriage which attaches to the door there is a black adjustment nut with a spring on it. Tighten it up more by turning it clockwise until the belt tightens up. The belt will droop a little when the door is all the way shut normally but should not during operation. If you tighten it up too much the belt will slap on the rail during operation. Make sure the spring is set on the adjustment screw too. This holds the belt tight over time. Thanks BB

DOES IT REVERSE OR STOPS BUT NOT TOUCHING THE FLOOR?

IF IT DOESN'T TOUCH THE FLOOR YOU EITHER NEED TO ADJUST THE DOWN TRAVEL OR LENGTHEN THE CONNECTING ARM.

IF IT REVERSES YOU NEED TO DETERMINE IF IT IS THE SENSITIVITY OR THE SAFETY EYES.

I just had that problem this morning and the cause was that the springs that help hold the weight of the garage door were broken. This caused the garage door opener to raise the garage door a fe inches and then drop again. We called in a professional and $200 later we had new springs and everything works fine now.

It sounds like you may have a spring problem. Release the door from the opener and see how it acts manually. Open it as far as the opener does and then see what happens when you release it. Also the weight of the door should give you a clue.

You could always use "Belt Ease" from an Auto Parts store. It's made for squeeky belts.
-Lonnie