Garage Door Opener Repair tips PT1 long

techdave(SoCal)January 26, 2006

Hi all, it seems to me that in general GDO posters are not having as much success at instructed self-repair as tractor owners, and that poor Don is innundated with requests for assistance.

To try to relieve some of Don's load and make others more capable of diagnosing their own situation I offer the following guidlines to understanding operation of certain GDOs. This is to facilitate diagnosis and repairing most common and FUNCTIONAL problems on late model craftsmen GDOs.

First off, when in doubt, dont. That means if you have any doubts about your understanding or capbilities to fix it SAFELY dont mess with it, get pro to do it (same for tree work). Deadly forces and weights and tensions are present in the door-opener-house-customer system.

Second, even though we all use opener, the actual name is garage door OPERATOR. They are not intneded nor designed to lift (OPEN) the weight of the door. If the door and its hardware and jambs are not in good balance and repair they should be made so before proceeding. To some extent the safety systems built into the GDO are negated by the home defects mentioned above. Chainbreakage during operation of unbalanced doors aint pretty!!!!

Third, if you have an older gdo without so called optic sensors that mount on the doorjamb and it is giving you problems/fits, REPLACE IT. Why mess with a unit that is significantly less safe than current standards. ****please**** DO NOT ATTEMPT SELF REPAIR OF OLD BELT DRIVE GDOS, except maybe to change the belt. They have lots of hot spots on the chassis, parts are mostly NLA, most of the force adjustments are primitive and subject to dangerous innacurcy with wear and corrosion, and movement of the pulley with the unit plugged in can cause IMMEDIATE MOTOR START UP!!!

If you can safely use a ladder, unplug a powercord, work with your arms owvrhead you can probably fix your gdo OK. possible EXCEPTIONS, intermittant problems, phantom opens/closes. and range/interference problems. These are relatively rare to very rare problems.

To start understanding the GDO, the door must come first. All common doors have some type of spring or weight to offset lift of the doors weight. Cables or linakges join the spring or counter weight to the door in some fashion. All should be checked for obvious wear or looseness. But mostly all you need to know for DIY is that the door must move smoothly thru its full range of motion. only light to moderate hand force should be needed to open or close th door gently. No more than say a middling to heavy bag of groceries. Stop here and remdy this if this is not true. TO TRUELY UNDERSTAND IF DDOR BINDS IT MAY BE NECESSARY TO PUSH OR PULL THE DOOR FROM WHER THE GDO ATTACHES TO IT. Especially for the following close problems:shaking on the close of one piece doors and force reversals on close of sectional(so-called roll up) doors.

The sectionals may rub the jamb when pushed closed by the gdo but not do so if you pull them down byhand. One piece door systems may shake on start of close if pushed closed by the gdo arm when they were opened to fully flat. This often not a gdo problem per se, but problem with installation or maintenance of the door and/or opener. Only typical GDO problems that MAY contibute to one piece door shake are loose chain or worn trolley parts.

How it works...GDo motor makes power, moves it thru belt/chain/cable/screw/linkages in some form to push on the door or pullon the door. TRAVEL adjustments (aka Up or Down limits) are used to shut off the gdo motor when the door is at a desired point of travel. FORCE limits are means to limit the amount of push or pull the motor will exert against resitance. When the up or down force setting is exceeded the motor will stop. This to help protect the door, people/pets, and vehicles. There is also an rpm sensor that checks ot see if the motor is turning. typiclaly this is onlyused on the close, and is a backup to the force adjustments. If the motor stops rotating or the sensor tells the mainlogic board it has stopped the door wont close as the gdo thinks its crushing something.

Do the force limits first with a working remote n yor hand. Do not do this step if you are feeble, in-agile, or have backproblems. Close the door, and as it closes resist with a firm pushof your hands when the door is about waisdt high. DONT GET UNDER DOOR. it should reverse, if not lower downforce and try agian. AS the door reverses and starts up, (after successful downforce adjustment), reach up and pull down sharply on door, it should stop. if not lower upforce. Try again. Limit adjusts to follow in another post.

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Good infomation, I had no idea what all is involved with a GDO
I did see Don takeing alot of questions, and doing a great job. Probably be easier to just make a pdf or some such to share with others ? It appears most have lost or never had a manual,in my old age i even learned to read and KEEP manuals :)

    Bookmark   January 27, 2006 at 1:30AM
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I replaced drive gear & worm set in my opener,& when i tried to use it, it closed & continued to run i pulled
the emergency cord & it run all the way out, i can,t get
it to reverse. can some one give me an idea what caused this?

    Bookmark   February 20, 2006 at 10:58AM
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Hi Larry, sorry but ai cant undeerstand your post at all. Please try to repost it more clearly on its own thread. Sorry Dave.

    Bookmark   February 20, 2006 at 10:02PM
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I think I have the same problem as Larry_mechanic.
I replaced the worm/gear on a Sears 1/2 hp 139.53915SRT.
I thought I did it per instructions.
On hitting the button, the trolley would go towards the door and then reverse about a foot. Thinking that the GDO was confused as to where it was, I reinstalled the chain with the inner trolley(outer trolley disconnected)all the way back to the GDO - in the open
position. So now it goes about a foot forward and then reverses back to it's start position.
I'm pretty sure I messed up the gear installation and would
appreciate knowing where to look. Limit switch? RPM sensor?


    Bookmark   February 24, 2006 at 7:36PM
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lunasea grady, did you remove the black plastic interruptor cup from the shaft of the motor. Sounds like you need to replace it.

    Bookmark   February 24, 2006 at 7:57PM
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I don't remember but I did try to follow the directions. I'm sure I have to take it down and open it up. Does the cup have to be aligned in a special way?

    Bookmark   February 24, 2006 at 8:39PM
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Hi lunasea, it does not need to be aligned, but it does have to be fully seated on the end of the motor shaft, and the wires to the rpm board must be put back on.. HTH Dave.

    Bookmark   February 24, 2006 at 9:59PM
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This must be a common problem, Because I am having the same thing happen.

    Bookmark   February 25, 2006 at 3:10PM
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The trolley will go 1 foot forward then one foot back when you're stupid enough to plug in the RPM sensor plug incorrectly - missing the top pin.

I also found that in fooling around in this area that you need to make sure than the plastic housing holding the nylon screws that travel for the up & down contacts needs to be securely in place. Otherwise the little worm gear on the vertical shaft won't engage the horizontal worm gear on the center shaft of the three screws. Then the limit switches don't stop the motor.

I thank you guys for pointing me in the right direction.


    Bookmark   February 25, 2006 at 7:45PM
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Does anyone know how to reset the main controller for a "Sears Best 1/2 HP" garage door operator? It was installed before I bought the house about three years ago. It has the optical sensors, so I do not think it is an old unit. Yesterday I accidently hit a combination of the lock button and I don't know what on the garage wall controller. Now the remote controllers only work to open the door--not close it. To close the door, I have to press and hold the main power button from inside the garage. Of course, I do not have an owners manual. Your assistance would be appreciated!

    Bookmark   April 16, 2006 at 8:42PM
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Sounds like the sensors in the doorway are not properly aligned. Make sure they are pointing at one another and the small light on each one is on and not blinking.

    Bookmark   April 17, 2006 at 1:29PM
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Don, You are a VERY wise man! I didn't know there were these two lights. One was out. I shifted the connecting wire & the light went on. I just closed the door with the touch of the button. Thank you!

    Bookmark   April 17, 2006 at 7:25PM
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This GDO section has got to one of the best if not the best "do-it-yourself" repair sites around. I read everyone's postings and then figured out the problem for my inoperative GDO and then to fixed it. Saved me a least a hundred dollars in service call fees. Thanks a bunch to everyone.

    Bookmark   January 22, 2007 at 1:57AM
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I am having problems with my GDO optical sensors. When the sun shines on them at just the right angle my door won't shut. i have to get out of my car and stand in front of them so my shadow covers the sensor - then it closes no problem. Has anyone else had this problem? If so, how did you fix it? Any ideas?

    Bookmark   April 6, 2007 at 9:37PM
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Sun interferes with Garage door sensors. I'm having the same problem. I don;t want to place them together because I have a little girl to protect, but don't want to have to get out of the car to shut the door either. If anyone has any ideas of what I could do it would be great. Please email me.

    Bookmark   May 10, 2007 at 8:31AM
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If the sun is only hitting one sensor and not the other when having this problem you might try swapping the sensors from one side to the other.

I'm thinking that if the sensor emitting the beam is getting direct sun light it might help to put the receiving sensor in it's place instead.

Just a thought.

    Bookmark   May 28, 2007 at 10:27AM
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Slightly repositioning the collar 5/16" (8mm) from the end of the motor shaft, allowing the RPM sensor to detect a "properly seated" interrupter cup, resolved a "short cycle" issue with my opener after replacing the worm gears.

    Bookmark   February 3, 2008 at 12:08PM
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Help... please!!!
My eight year old child thought it would be a good idea to pull the red rope on our opener today.
I don't know how to get it back to working again. I'm sure there is probably a simple fix, but I was too frustrated to deal with it this morning.
Any help?
Thank you so much!!

    Bookmark   May 8, 2008 at 9:59AM
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Hi Shelly: If the door is in the closed position, lift it up a little bit, and the two pieces should "snap" back together.

If the door is open, use your remote to move the trolley to the up position, and then move the door alittle bit until th etwo "snap' together.


    Bookmark   May 9, 2008 at 1:51AM
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Having problems with new install, help needed. thanks in advance.

I have installed Overhead 4040L GDO with belt. I have followed the instructions and mounted the railings and the main unit. I could see that the motor is rotating and pulling the belt, however the door doesnt move??? The Curved Arm that connects the door and the carriage is properly connected per the instructions. I could see that the belt is around 4-5' longer and lose, should I be reducing the length will fix my issue?

The door is 7'1' height and 9' width. The railing is around 9'5' and its a 1/2 HP DC motor.

Please let me know. Thank you once again.

    Bookmark   July 3, 2008 at 4:42PM
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Any good way to disable the motion detector during very hot days. I will be replacing this unit as soon as possible but until then I would like for my Wife to be to close the door from her car.

    Bookmark   July 9, 2008 at 10:26PM
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I have a craftsman model 139.53673srt3 garage door opener, mfg date 9/98. I replaced the drive gear and worm gear. I reattached the chain while both halves of the trolley were mated. The door opened about a foot then stopped. I pressed the remote again and it closed about 5 inches, then back up 5 inches. I have tried the following without any progress:

1. I adjusted the up and down force.
2. I adjusted the up and down limit.
3. I removed the chain, pushed the remote button until the sprocket rotated in the clockwise direction, then pushed it again until it stopped (this took several attempts to get it to stop without reversing counter clockwise). Reattached the chain with trolley coupled with the door. The door opened 12" and stopped. I pressed the open button again, and the door closed 5" and opened 5". I pressed the button again, and it closed 5" and opened 5".
4. I tried the same as in #3, except I did not mate the trolley with the door to observe the travel distance. The trolley traveled down 5" and then up 5".

I noticed that the red led flashes a few times, then goes off, flashes a few times, goes off. The led continues to do this until I unplug the power plug. The opener light bulb does not flash at all during this.

The sensors are working, when I walk through the open doorway, the opener light turns on.
All the wiring appears to be plugged in correctly so I'm puzzled why all my adjusted are have no effect whatsoever.
All of these adjustments have been made with the opener cover off. Will the cover being removed caused these problems? There doesn't appear to be a lockout switch that would prevent the opener from operating with the cover off.

Note: I had a problem when reassembling the shaft bearing kit, forcing the outer collar against the spring loaded washer snugly, and tightening the set screws at the same time. It took awhile but I got it got it as best as I can. The Interrupter cup seems to be on ok, but it does look like there there is only 1/8" clearance between it and logic board.

Thanks, Ted.

    Bookmark   February 16, 2009 at 10:53AM
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It is not the door sensors and there is no lockout switch to worry about. The LED is trying to tell you something. It sends a trouble code. You need to count the flashes between the pause. It will repeat the code. If it is a 5 then you do have a problem with either the interrupter cup or the RPM sensor board. Make sure it is plugged in. If you didn't get the bearing, collar and washer installed properly the motor shaft will shift and the interrupter cup will move from between the infrared sensors causing the door to reverse.

    Bookmark   February 16, 2009 at 6:30PM
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I marked the location of the outer collar on the motor shaft with a Sharpie. I loosened the set screws on the outer collar. Using a vise grip, I was able to push it up against the spring loaded washer, while I tightened the set screws. I reinstalled the interrupter cup, and plugged in the cable, with the metal contacts side of the connector facing out. It is snug and straight on the motor shaft. It appears to be about 1/6" further forward on the shaft than before. To make sure that the motor was not out of phase, I removed the chain, and using the remote, pushed the button until I was able to stop the opener in the clockwise closed position. I reattached the chain, and with the chain half of the trolley disconnected from the door trolley, push the remote button. No change. The trolley moved down 5", then up 5". The LED flashed 5 times then off, 5 times then off. I watched the rotation of the interrupter cup, and it spins straight and true on the shaft, and between the RPM sensors. So it appears that the RPM sensor board is defective. Would the RPM sensor failing cause the gear failure or vice versa. Or is it likely that it got zapped by ESD while I was disassembling the drive and worm gears (I didn't ground myself with a wrist strap). Are the sensors supposed to light up when functioning? Approximately how much does an RPM sensor board cost? Should I just replace the RPM, or do you recommend removing the chain, rotating the motor then stopping it in the downward direction, after replacing the RPM, to get it in the correct phase? Any step by advice you have would be helpful. Thanks, Ted-

    Bookmark   February 17, 2009 at 12:57PM
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That code is for RPM sensor or motor overload. We know it isn't a motor overload because the motor is running. The only thing left is the RPM sensor. You can't see a light on it because it is infrared. I don't think there is anything left but it. Static electric wouldn't have hurt it. Make sure there isn't anything between the two small sensors on that board. I have heard of spider webs causing a problem but have never personally seen it. Maybe remove the cup and run a cotton swab around there.

    Bookmark   February 17, 2009 at 3:59PM
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Sheesh! After reading all of the problems with GDOs' in this column, I have made up my mind that I'm not going to have one of those trouble-makers on my garage door!
When i get too old and feeble to open the door by hand, i'll park the car outside, and keep the door shut! And only open it by hand when i do need to use the garage.
Also, how much energy does it take to get the door open, back the car out, get out and close the door, get back in and drive off?!?! Most modern folks are too fat enyway, from their lives of leisure, and that bit of exercise would do them a plethora of good!

    Bookmark   February 20, 2009 at 10:49AM
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I replaced the RPM Sensor, readjusted the up/down travel, up/down force and that did the trick. I did find that I had to disengage the trolley, remove and reposition the chain with the door opened, in order to have the door open as high as it once did. So, for total expenditure of about $50.00 in parts (drive gear/worm gear kit, rpm sensor,), not to mention blood, sweat, tears, and nearly frostbit fingers, the opener will hopefully last another 10 years before any problems arise. Thanks again for all you help, Ted-

    Bookmark   March 4, 2009 at 10:57AM
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Rusty go back and hammer some more on your lawnmowers. This is a technical forum for the enlightened.

    Bookmark   March 4, 2009 at 2:36PM
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The sensors on my opener are not working. The infrared light is not lit. It may have been bumped or affected by a power surge from a recent storm. Is there anyway to repair/replace the light(bulb) and not have to replace the sensor units. The sensors appear to be fine otherwise. I am experienced at repairing various appliances and electronics, so I'd like to attempt a fix first. Thanks

    Bookmark   August 5, 2009 at 11:03AM
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As a followup on the sensors: I opened the sensor with the infrared bulb in it. When I push on different parts of the back of the board, the light comes on. As soon as I stop touching the board, the light goes out.

    Bookmark   August 5, 2009 at 11:40AM
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You cannot see infrared. What bulb are you looking at?

    Bookmark   August 5, 2009 at 4:16PM
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the larger of the two sensors has a red light at the top and a clear (sensor) lense in the middle. The red light may just be an indicator light, but when it is lit, the opener works. I am not sure if the infrared beam is emitted through the clear lense to the sensor on the other side in order to complete the circuit. The odd thing is that I can push on the back of the circuit board in a couple different places and make the opener work. It doesn't appear to be any one component that is bad.

    Bookmark   August 6, 2009 at 10:31AM
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Okay I understand now. You are correct the lights you can see are an indicator that the sensor is working. It sounds like you have a bad connection on the circuit board or maybe bad wiring. On earlier models the wiring had small push on connectors that corroded and became intermittent.

    Bookmark   August 6, 2009 at 11:01AM
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I have a Sears Garage Opener Model 139.664956. The opener is functioning ok but the remote control (139.53879) is dying, so I bought a universal remote that should be compatible. However, I can't find the button on the motor that you are supposed to press to re-program it. Guidance would be helpful.

    Bookmark   August 8, 2009 at 12:44AM
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My Craftsman GDOperator model #139 53924 is working fine but the light, which is apparently sound activated, comes on and does not go off unless I hit the light button, clap my hands (which turns it back on), and then hit the button again. (or hit it once and then sneak out of the garage.) Lacking a manual I'm not sure what to do short of unscrewing the bulb. Ideas?

    Bookmark   August 8, 2009 at 2:49PM
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robinlt98 your opener is so old it did not have the button you are searching for. It had a series of small switches called dip switches. I doubt even if you still have the original receiver for this opener and you will probably need an expert to help you. I recommend you replace this thing with a new model that is not only state of the art but is much much safer than what you have.

barbaralst I think you will find your wall control detects body heat and this is what is turning your light on. To disable this feature, slide the Detector Switch on the right side of the door control down (off).

    Bookmark   August 10, 2009 at 11:23AM
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I realize this is an old discussion, but it comes up in Google searches. I made a web page with the scanned instructions and pictures for changing the large gear, and the instructions tell you how to reset the travel limits etc. In case anyone needs that:

Here is a link that might be useful: sears garage door opener gear repair instructions

    Bookmark   April 3, 2010 at 5:33PM
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I have a Craftsman GDO that suddently developed the following problem. When closing the door with a remote the door will only travel a few inches and then stop (as if it struck an object) and reverse direction. I have to repeatedly press and repress the remote to coax the door all the way closed. When I shut the door with the wired button it will close all the way only if I keep the button depressed until closed. I have NO problem opening the door.

I have adjusted the tracking force and distance switches and unplugged and replugged the unit to no avail.

Thanks for your help.

Ron Licata
Weathersfield, CT

    Bookmark   January 3, 2011 at 2:15PM
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Make sure your door sensors are pointed at one another and the small light on each one is lit and not flickering. Tweak them a little. If you cannot get both lights to come on you have a bad sensor.

    Bookmark   January 3, 2011 at 3:05PM
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Don - I tweaked them a little and it worked!!!

Thanks - you just saved me some $$$. I appreciate it.

Ron Licata

    Bookmark   January 3, 2011 at 4:07PM
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I have a 3/4 HP Sears Craftsman GDO that will not operate. I've checked that the unit is getting power. The overhead lights come on and there is a sound that the unit is trying to operate, but nothing happens otherwise. The trolly is engaged and the door hardware appears to be fine; no broken springs, or misaligned cables or pullys.
I do not have the manual. The unit is a newer model; about 7 years old.
Any ideas on where I need to start with this repair?

    Bookmark   May 31, 2011 at 1:52PM
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