Why is my garage door suddenly reversing when going down?

check down force adjustment. will it go down if you hold down the wall control button?

Check that the wheels and bearings are turning freely and that the door is not cocking to one side when closing. If the wheels are catching because of bad bearings, because the tracks are out of true or because the door is not staying straight in the tracks, the motor thinks that the door is hitting a car or a person and reverses. One thing to try: disengage the motor and try moving the door through the full traverse. Most automatic doors have a pull-cord that disengages the door from the motor. CAUTION: You may need a friend to help with the door, because it could be surprisingly heavy,.

your chain is in the wrong position, unhook the chain and run the door opener so it is in the down position, then reattach the chain and make the adjustments as needed on the up and down screwes located on the side of the unit. good lick

If the main light flashes 10 times when the door reverses it is a sensor problem. Check them very closely. If they are just a little off one of them will be flickering but it is difficult to see. This can also cause the problem to be intermittent. Tweak them just a little.

It is normal for that light to blink randomly.

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.

A couple things to check and do. If the main light flashes 10 times when the door reverses to the open position it is a door sensor problem. Make sure they are pointed at one another and that the small light on each one is lit and not flickering. Tweak them a bit if necessary.

If the main light isn't flashing it may just be a simple adjustment. Locate the 'down force' adjustment on the rear of the motor unit near where all those white wires go. Increase this about 1/4 turn and try.

For the light you should unplug the unit and then using a small screwdriver pull out on the center contact in the light socket.

On the back of the motor unit you will find a control 'down force'. Turn this about 1/4 turn and try. This is for the reversing after moving a foot or so. Do not increase this control too much as it affects the safety.

If the door is hitting the floor and then reversing you will need to adjust the 'down limit' which is on the side of the motor unit. It takes a small screwdriver and you need to turn this control in the opposite direction of the arrow printed on the cover. Some tweaking will be necessary and remember if you run the motor too much a thermal switch will shut it off and you will have to wait 15 to 30 minutes for it to cool. This is normal so you will not be hurting anything.

When garage doors get sticky, bent, and the chain needs lube they will trip the controls. A door may suddenly reverse for no apparent reason, that is friction. A GFCI is real sensitive to load. Also check the wiring to the unit. Any bad connection will upset the GFCI. Check all the way back to the breaker box, sometimes the screws on the wires need to be tightened.

door will not close all the way. will go partway down then reverse itself.

try adjusted the sensor controls on the sode of the unit other wise replace the logic board
http://www.chamberlain-garage-door-openers.com/circuitboardcompatibilitychart.htm