I have a dimmer switch with two controls each controlling different set of lights. L1 in each is connected with blue and yellow. Red is connected to one Com and another wire connects both Com.
I have a new switch
Wanted to check if I follow similar patter do I have to connect both coms?
When changing any switch like for like, the wires should be connected in the same configuration in the new switch as they were in the original switch. Failure to do this means the lights will not work as they did.
Yes I agree not good markings, but Com is marked with AC sign with arrow through it, so line in to Centre Com and Line out from L1, or L2 swapping L1 and L2 changes which way is off and which is on.
Since red is linked one would assume red to centre.
The new switch will not work as it should because you have wired in incorrectly.
Look at it this way. The old switch with the old wiring worked. The new switch with the old wiring does not work, it only does not work because you have wired it wrong, you have proved that by saying one light does not switch off, so since the wiring is the same as it was, the switch is brand new, it must be wired wrong.
If it helps, your new switch is the same as the old switch, but it is two switches, one is upside down in relation to the other, a lot of folk get it wrong because of this.
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