LiftMaster 373LM Three-Button
Started update: 08/15/2017
Last update: 08/15/2017
Garage Door Opener Repair
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
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.
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.