I am attempting to replace a lighting fixture in my shower. The light has broken and so has the unit that holds the light.

I have a new one and am putting it in. As you can see in this picture, there are 2 power supplies - the black one (original) and a new one (supplied with the LED light fixture.

The issue is, when I turn the mains on, the fan still comes on, but the light does not show.

I tried to remove the LED driver (the white one), and when I added power, the LED flickered a little but only when the power source was turned on.

I am unsure what to do to get the light to work as all the tutorials show to do what it looks like I've done (add the LED driver and then the LED light).

As you can see, the cable from the original (black box) goes into the input (although it's spelled intput on the box??) of the LED driver (white).

I have assumed the wires can go either way - just as long as it creates a circuit?

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  • This area is new to me. So, if you are referring to the black/purple wire going into the white LED strip, I've tried it each cable in each socket - nothing changes @Tetsujin
    – Dave
    Jan 1, 2022 at 11:01

2 Answers 2


That is not correct. You have the 11.8V AC (low voltage) output of the old power supply connected to the line-voltage input of the new power supply. That’s wrong and it won’t work.

Disconnect the line wires from the input of the old power supply and connect them to the input of the new power supply.

The two power supplies have different output specifications - it is important to use the one that came with the new light.

Power supplies are also usually the thing that actually fails when LED lights stop working - the old one may be dead.


The old power supply outputs 12 volts AC intended for older 12V lighting designs (may work with LEDs but probably wouldn't dim).

The new power supply outputs 12 volts DC. However I don't see any recognizable testing lab marks on it, which suggests to me it's cheap Chinesium that you got mail-order, which is probably not a safe device.

Your idea of connecting the 12 Volt AC output of the first power supply to the 120/230V AC input of the second power supply, gives me great concern as to whether you should really be "playing with power" as it were. This is a super basic error, and that particular one won't kill you, but lots of others will.

I would have you buy a voltmeter, set it on "AC scale", and measure the output wires of the old power supply. If it is outputting 12 volts AC, then it is not broken. In that case I am confident you can work on the low voltage side of the power supply with no safety risk. So I would suggest looking for a different LED light that can accept 12 volts AC, which may not be the one you have. (or may be).


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