Light Duty Commercial opener repair, conflicting expert advice??

Hi Folks,

I have a Liftmaster LG05011L, hi lift light duty commercial door opener made/installed in 2000 on a seldom used high lift garage door.  Three years ago while lowering it caught a board in the track and sprung the cable.  I called the original company who installed it and their repairman re-wound the cable and repaired it for $125 house call.  Last year the same thing happened again, it forcefully came down deflecting/spitting out the board from the track almost hitting me.  I re-wound the cable myself, and it operated seemingly fine but I could not properly set its limits, so I operated it manually for the last 12 months.

I called the same company as before to come.  Repairman arrived and I explained what happened to door recently and in the past.  I questioned the door sensitivity setting by the last repairman there since it seemed to really forcefully strike the board with such force that it shot it out the side.  He explained that the last technician that came was since fired.  He adjusted the limits (he seemed to struggle with this??) which worked fine for one cycle.  But once the door was tested/reopened from the closed position, the motor sounded fine but for the first 12" or so traveling up the door seemed to be slipping, going up more slowly than normal while rising, and then it regained its normal speed at about 12" high and continued all the way up and stopped.  But when reactivated and coming back down at normal speed it appeared to have lost its down limit and stopped a foot off the ground.  This point was at about the same point its upward motion "slipping" stopped and began its normal speed.

Repairman reset limits several times but same problem continued to happen.  Repairman was baffled, couldn't find any bent/broken sprockets, chain was fine, tension good, and then called his boss, company owner.  Boss said improper sensitivity setting had nothing to door with the door forcefully spitting out the board obstruction, and nothing to do with current malfunctioning problem at hand.  Boss said unit was toast, suggested a new model, Liftmaster #8500W Side Mount Opener for a total cost installed of $917.40.

I emailed Liftmaster tech support and they responded by suggesting a replacement unit of # MJ5011U.  I asked them if a motor replacement would be sufficient.   The responded yes, motor # 041D4509, about $150.  I'm somewhat mechanical and feel I could do the motor install myself.

But before I go through the purchase and installation, I wanted to seek some guidance.  From "qualified experts" I've been given two different replacement unit numbers and then a motor replacement suggestion. ????  It would seem to me to be more of a setting or clutch type problem than a whole motor or unit replacement, but I just don't know.

Any suggestions would be greatly appreciated.

Thank you
Ed

well, i think man you are really passing from a serious problem man! And i think that your old company that installed your device and other stuff will be cheating on you, More of these companies are only the sake of money ,can you tell me where is your current location so that i can suggest you the best garage door as because i have got a lot of friends who are in this business.