Electrical wiring to indoor light switch -- two black hot wires or one line/load wire?

Question

I'm replacing a light switch that controls outdoor house lights with a hardwired timer switch. I tried attaching one of the top black wires in the pictures below to the timer's line wire and I attached the other one to the load wire. The lights outside remained on and wouldn't turn off. I then switched the two wires around and now, 3 of the 8 lights permanently stay on whereas the others shut on and off properly, but all the lights are significantly less bright than they were before. Not sure where I am going wrong here, unless both wires are "hot" wires and should be tied together to the timer's line wire? Of note, this is the only switch controlling the outdoor lights. A pen volt meter arrives soon from Amazon.

Pics:

Thanks.

Answer 1

A timer needs power. It can get the power one of 4 ways:

• Battery
• Neutral
• Ground
• Leak through switched hot

Each of these has advantages and disadvantages.

• Battery powered timers can be installed anywhere, but they need periodic battery replacement.
• Neutral powered timers require a neutral so they are not an option if you don't have the correct neutral readily available.
• Ground powered timers can only use a little bit of power and don't play well with GFCI circuits.

And, as you have likely found out the hard way, leak through switched hot does not play well with LED lighting.

In general, timers need to be installed the "right" way. Install them backwards and they will often not work. That is different from simple switches which don't care where you put the hot (line) and switched hot (load) wires.

The good news is, it looks like you have neutral in the box - all those white wires in the back. You need to make sure you have the matching neutral for the hot wire. The hot wire should be the wire that goes to two different switches. Assuming you have that neutral available, get a timer that requires neutral and that says it is compatible with LED lighting and you should be all set.

Answer 2

Switches have 2 "sides": Supply (always-hot) and switched-hot onward to the light.

The "same wire" wire notably stops here and goes to another switch. Only always-hot/supply will do that. So we just ticked that box; we now know what it is.

The other two wires on your old switch must therefore both be switched-hot. That's unusual but not impossible. Noting that you have 3 lights and 5 lights acting somewhat independently, my guess is that one of those wires feeds the 3 lights, and the other one feeds the 5 lights.

Anyway, those wires were together before. Note they were both touching the same metal plate before, thus connected before. You decided to separate them, I'm not sure of your reason and maybe you aren't either. But if you want it to work like it did before, don't separate them :)