Wife came home today and was able to open garage door without a problem, but when tried to close it, the unit hums for a couple of seconds and stops. No movement of the door.

I looked through the forum for awhile and saw some of the suggestions....the trolly was not up against the bolt, but I tried removing it and adjusting the Up travel away from the arrow without any success....still same hum and nothing else.

The Learn button diagnostic blinks 5 times.

Model 139.53914D

Any help would be greatly appreciated!

Thanks,
Matt

New home and new opener - less than a year old.

Door works fine manually - moves easily along the track. The manual suggests disengaging the trolley - closing the door - adjusting the up travel against the arrow and then hitting the button with the door closed....this should have caused the trolley to move away from the motor toward the door....but I still just get the same hum.

A couple other things I've tried after reading this forum...

I unplugged overnight and then plugged it back it and gave it a few minutes hoping it would reset.

I also stood directly in between the sensors in the doorway and hit the button to activate and got the rapid clicks - so I don't think that is the issue.

Other than when I intentionally block the sendors, I get the same 2 second hum followed by the lights coming on.

Thanks,
Matt

Take a look at the trolley. It is that silver thing thats riding on the black rail. Your chain or belt attaches to it at both sides. Make sure it is not jammed up against a stop bolt either in the up position or the down postion. If you can't tell by looking at it, take the chain off the sprocket and hit the button if the motor still just hums for a second then it is bad if it starts working then the trolley is jammed and needs to be freed.

If you motor will run and not open the door you have a stripped drive gear. So if you hit the button and you can hear the motor humming until you hit the button again then the drive gear inside is stripped needs to be replaced.

I have a 1/2 HP Craftsman Belt Drive Garage Door Opener. Part # 41A5021-2B. Model 139.536645RT1.

My opener was working, but the belt was not moving. similar to a problem stated above. I opened up the cover and it was quite clear that the drive gear was stripped. There were plastic shavings from the gear all over the inside of the unit. The gear was completely dead - it could not grip the screw-drive.

I searched Sears and the internet for info on this model number with no real luck - just a few leads. This was the only site that had a forum talking about it.

I went to my local Sears parts supply and got a replacement. There was just the gear and related pieces for about $24. And there was a gear and sprocket set for $8 more. Since the gear is mounted onto a shaft that turns another gear that moves the belt, i bought the entire assembly to save some time.

Turns out that it was not the right piece. It was an assembly for a chain drive unit - even though the salesperson said it was made for my unit. Also, there is a round cover that screws into the chassis. The replacement piece was completely round, where mine has an arc cut out of it. This is important as a completely round piece would not have fit on the chassis properly.

I wish that she would have sold me the entire assembly for a belt drive, because i decided to just take the gear off the new assembly and replace mine with the new one. That was a major hassle as there are two small pins holding the gear in place and they are really hard to get out. I had to improvise a tool to get them out.

But once I replaced the gear, everything else was really pretty easy. The disassembly and re-assembly went quickly without incident. There are instructions that come in the kit.

Everything is back up and operational.

If your door crashes down when you close it there is definitely a problem there that needs to be tended to. The springs on the door are there to compensate for the weight of the door. It should not be that heavy.

If you are not comfortable with removing the logic board maybe it is time to call for help and have the door checked at the same time.

Replacement sensors are available from sears. The door should still work going up and should still go down by manually holding the wall button for the full closure.

If nothing is working then the problem is not necessarily related to the sensors.

Hope that helps.

Any help?

I appreciate anyone helping me to get this going again. I've followed the instructions on back of unit and in the printed manual to no avail. Instructions say that the opener light should flash while holding in the buttons, but it never flashes - it just stays on a few seconds and then goes out.
I must be missing a step or something...?

Inside the unit find the up/down travel adjustment mechanism(see photo). At the end opposite the screw-heads you turn to adjust the travel there is a gear mechanism. When these gears wear they can slip. In addition, the chassis for the gears is plastic and over time will weaken-my opener is almost 12 years old! My gears are still in pretty good shape. The problem is that the chassis would flex and allow the gears to jump hence, the reason my adjustments would work for a while then the problem would come back. Now I know this will sound like a hokey fix but I figure it is better than dropping a couple hundred bucks on a new opener...I pushed a toothpick into the hole in the main chassis where the travel mechanism is snapped in essentially eliminating the chassis from flexing and allowing the gears to slip. make sure you do this on the side opposite the gears. If you do it on the same side you will put a larger space between the gears making the problem worse. This has been working for nearly a month now. I attached a picture of the travel adjust mechanism for reference. It is difficult to see the toothpick in the photo. It is right next to the brown wire connection opposite end of the mechanism from the adjustment screw heads.

One other hint: the opener will most likely get hot running the door up and down making your adjustments and will shut off (thermal overload protection). I don't know why but after this happened the green light next to the remote programming button on the back would flash 5 times-off-flash 5 times...repeatedly. I had to pull the power for a couple minutes to get the light to stop blinking. Either let the unit cool for about 10 minutes after it shuts off or to keep your unit from overheating, place a small floor fan in position to blow on the motor.

Craftsman 1/2 HP model# 139.53971SRT manufacture date: 02/2000

Thanks.