Two A/C units are close to each other and turning one on turns the other on. How to fix?

The remotes use infrared light to control the AC units. Because the AC units are both in the same general direction from the remote, the wide angle beam from the remote is controlling both units. I see two solutions:

• Move one or both AC units. I'm guessing it's not practical, or you wouldn't be asking for advice.
• Keep the bedroom door closed so light from the living room remote can't control the bedroom AC unit. It may not be the best solution, but it would work.
• Find a way to use the remotes without pointing them at the AC units. You could use strategically placed mirrors or IR remote extenders to redirect or retransmit the signals to the correct unit.

As already noted, the remotes use infrared light. The problem is that they all use the same codes. This is, in fact, why there are "universal remotes" for TVs - each manufacturer picks a set of codes and uses it for many different models of equipment, and for replacement of a lost or broken remote all you need is a remote that uses the same codes. With TVs this is usually not an issue as most people only have one per room.

The solution is to limit the range of the beam. First figure out where the signal is coming from. Typically this is on the end, but it may not be obvious. You can figure it out by selectively blocking sections of the remote until you find out which section prevents the remote from functioning.

Then make a cone or tube out of some material that blocks the remote and tape it around the signal emitter so that the signal will only be "visible" in a narrow area. You may need to experiment a bit to find an effective material. A solid opaque plastic should work (one site I found indicates that typical black plastic trash bag will transmit infrared) or cardboard (white paper will decrease infrared signals some but probably not enough).

Once this is done, you will need to aim the remote at one A/C unit and it should not activate the other unit.

I have 3 units air con of same brand in my office room. So all 3 units will turn on/off at the same time, by single one remote control. So I used a brown tape to cover the signal emitter to weaken the signal strength, and it works. But i have to place the remote control very near to the relatively air con, and i can control each air con individually.

Change the address on one of the units.

This manual (page 5) is for the L series units, but by memory the remotes and controls are the same/very similar.

Cut the jumper J4 in the battery compartment of the remote, and jumper JA in the electrical compartment of the indoor unit.

Be aware that the electrical compartment has live wires inside. Cut power to the unit before opening it.

Only do this on one unit, or you'll have the same issue again.