LiftMaster 373LM Three-Button
Garage Door Opener Repair

Started update: 08/15/2017                     Last update: 08/15/2017

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Problem: Even with a new battery (Li 2032 coin size battery) the units don't work. These units were about six years old when three of the four we were using started having problems. These three became intermittent at first and then all three failed completely.

RF Information: This device operates at ~ 315 MHz

Other Information: In general, the larger button is used to open the garage door and the two small buttons can be programmed to turn the door lights on/off.

Tests: I first suspected that the mini-temporary contact switches were getting dirty or becoming defective since these were mechanical. After changing one of the temp switches of one of the units, I found that this did not help. Quick continuity tests of all the switches of all defective units was performed and all switches were found to be working fine.

The next electro-mechanical point of possible failure were the battery holders. I tried an external power supply adjusted to 3.0 Volts and clipped onto the battery holders of all three units. This had various levels of success: one unit worked perfectly every time; the other two were, at best, intermittent. This was better than anything else tested, so a further test was performed on all three units.

A small hole was drilled into the cases so an external AAA battery holder with wire leads could be used to power the units. These battery holders hold two batteries in series for a 3-Volt power source. I used the part# BH-42 from http://www.allelectronics.com, a battery holder with short wire leads. I then tried all units and found them to all work perfectly. I added Velcro dots on the backs of the battery holders and on the window visors so the battery holders would not drop when the visors were used.

The bottom line is that all "defective" units were in fact working perfectly except for some kind of battery holder electrical problem. I did not bother testing, cleaning, or re-soldering the battery holder connections since I liked the idea of using more powerful batteries which were external to the case, making battery replacement easy.

If you have similar problems with your remote garage door openers I'd try cleaning, re-soldering the battery holder, and as a last resort, using an external battery holder soldered onto the circuit card power connections to see if this solves your problems.



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