In the past, I've forgotten many facts, so this may be long. (Also, I know just enough to be dangerous....)

Backstory: I'm putting in a LED Strip light in my pantry. It will be connected to a standard 120 outlet (already in place) The LED Strip uses a 12 volt power supply. I'm putting in a reed switch (Normally Open) to turn on and off the lights. The power supply puts out 1.2-1.5 amps and the reed switch is only rated for 500 mA so someone suggested using a relay. I'm using this light set , this relay and followed this video in hooking it up. Below you can see my work. (The black box will hold the relay and keep it from being bumped by stuff stored in the pantry.) From the reed switch to the relay, I have approx 8 feet of #18AWG solid wire. This wire, internally is White and Red. The wire is connected to the reed switch with wire nuts and tests very secure. The reed switch is connected White to White, and Black to Red on the wire. (The brown wire you see in the pic is this red/white #18Awg)

It won't turn on.

Before I hooked this all up, I tested the power supply to make sure which wire was which (all I knew was one side was marked and the other not.) The marked side was found to be negative and the unmarked side was found to be positive. How did I test? I used a electrical meter, with the black on ground and the red on the wire being tested. I got nothing from the marked wire and I got power from the unmarked.

When the power is plugged in, a green light can be seen on the relay itself. BUT, when I touch the magnet to the reed switch, nothing happens. (In case someone wonders, you can also see a very short brown wire connected at the Reed Switch. This is the NC connection and since it is not used in this application, I cut it off and used it for the NO to DC- connection required on the Relay.)

The second pic below is how all this is connected. I hope I've given enough information, I will of course, add more if needed. I've gone over this diagram and my connections and all seems correct, but the fact that the lights don't come on....well, something is off.

So, what might it be?

 

Check your relay wiring instructions. Does the other side of the magnetic contact go to Negative or Positive? Your drawing shows it going to Negative.

If the magnetic contact is marked in accordance with the National Electrical Manufacturers Association standards, the contact circuit will be Open when the magnet is away from switch. That is electrically normal; with no external forces acting on the switch. Just like a relay.

 

I agree. The white switch wire should be on DC+ not DC-.
You are switching power to the relay.

Those isolated relays are a little tricky to wire.

Those mag switches are form C. You should be using white and brown.
white - common
black - normally open (closes when magnet is near)
brown - normally closed (opens when magnet is near)

 

This may be my error. I want the switch to be OPEN - no current - when the magnet is near...so I used the wrong wire? I (luckily) got two in the set and will swap them out tomorrow and see. Thanks.

I'm unsure here. there are NO markings on the switch at all.

 

@PJMAX Ok, I tested again this morning and want to be sure of what is what.

Testing across the white and black with NO magnet near, gives me a reading with an Ohm Meter. Is that NC or NO? I'm so confused at this point.
On a lark, I switched the connection at the NO post and moved that wire to the NC post. (The wire now goes from NC to DC-)
The light comes on, but when the magnet is brought near, the light stays on.

 

You want the switch to present a short to the relay when no magnet is near it.
When you close the door the magnetic gets near the switch and turns the light off.

Some of those switches have what can be called polar orientation.
Try putting the magnet near the switch from a different. side.

Try disconnecting one of the switch wires.... if the light goes off you'll know for sure it's the switch.
If you accidentally create a short across the switch... it can cause the contacts to burn closed.

 

I have tested the switch the day I got them to make sure they worked placing the magnet flush to the proper side.
It tested closed without the magnet beside it, Open with.

 

Ok, this is probably another case of me not knowing what I was doing, but things are working now.

Solution: This relay has a jumper for High or Low Level Trigger. I moved it and the whole setup works.
Thanks to you all for your input, I love this site, I always get good help, even if I am a dumass...

 

yeah 100% white wire is +

 

In your posted picture the jumper was in the right position (H) or I would have mentioned it.