There’s nothing more frustrating than completing your wiring for your new dimmer, getting everything installed, and then finding out that the dimmer is upside down.
Then you take it off the wall, check your work, think you’ve solved it only to replace it and find that the problem is still there. It happens sometimes.
There are several potential reasons for a dimmer being upside down, and they’re normally a relatively quick fix.
If the entire dimmer switch is upside down, including the dimmer slider, it may be mislabelled on the terminals. Reverse it. 3-way dimmers sometimes have the switch upside down, but the dimmer slider is right-way-up. This happens when a traveler terminal is mistaken for the common and can be fixed by moving wires.
There’s no harm in having an upside-down dimmer switch, providing it works, but most people like them to be right. So let’s take a look at:
- The wiring of a dimmer switch
- What causes reversed polarity
- How to fix it
Confusion Of Dimmer Switch Wiring
There are two types of the dimmer switch, and one of them tends to have more problems than the other when it comes to reversed polarity.
The less troublesome kind is the single-pole dimmer.
This regular dimmer switch is designed to control a set of lights on its own.
It has two main wires – a live and a load – and may also have a ground and neutral wire.
The live wire connects to the incoming power from the circuit breaker, and the load connects to the load – the lights.
Because these are really simple, it’s not too common to install the dimmer upside down. Still, some manufacturers may make them differently so that the switch is ‘off’ when the top half of the switch is sticking out.
The second type of dimmer switch is called a 3-way in the US or a 2-way in the UK and Europe.
These switches have an extra load wire, with both loads instead called terminals.
They’re designed for circuits where you’re wiring two switches to the same set of lights – such as when you want to control lights from both the top and bottom of a staircase.
With these switches, you would typically wire the live wire in the wall to the common terminal on the dimmer and then wire the two traveler wires on the dimmer to the secondary switch, which also has two travelers.
Then from the common terminal on the second switch, you’d wire in the load, which is the lights.
These extra wiring steps can cause confusion, especially as the wires are often the same color, so it makes sense to label them as you work.
The Cause Of Reversed Polarity: Switch Or Wires?
There are a couple of different causes for reversed polarity. Still, it will always be the switch’s fault – or the person who installed it, anyway.
The wires themselves don’t matter, and you can flip a switch any way you like, and it should still work.
Remember that at its core, a dimmer switch is just a switch with extra functionality, but it serves to break the circuit.
When the switch is in the on position, the current will flow.
So it doesn’t really matter if the live wire is wired to the load terminal and the load wire to the live terminal – it would still work because either the switch is ‘on’ and closed or ‘off’ and open.
And because of how junction boxes work, you can easily attach the either wire to either terminal.
This means it’ll always be the way the switch is wired that causes it to be upside down.
For a dimmer switch to be the right way up, the switch should be off when the top half of the switch is flush with the wall and the bottom half sticks out.
The dimmer slider should be at max brightness at the top, dimming the lights as it is slid down.
On switches where the dimmer is horizontal, the max brightness will be on the right and dimmed on the left.
Knowing this is good because fixing the problem depends on how ‘wrong’ the switch is.
How To Fix Reversed Dimmer Switch Polarity?
If the dimmer switch is upside down – both the toggle switch and the dimmer slider are wrong – then you just need to remove it and turn it the right way around.
It really is that simple.
You don’t need to re-wire it, just flip the physical switch around and screw it back into place.
The common issue is where the switch is upside down, but the dimmer slider is the right-way-up.
And this can happen in one of two ways:
If it’s a single-pole switch, it’s a problem with the switch – either it has been designed that way, or it is a bad switch.
You can either live with it or replace it.
If it’s a 3-way dimmer, then this is a frequent problem.
You’ve accidentally wired the live wire to one of the traveler terminals instead of the common terminal.
Sometimes this is just human error, but sometimes the switch can be mislabelled too.
So check first whether you’ve made a mistake and wired the live wire into a traveler.
If you have, move it to the common.
If it looks like you’ve wired it correctly, then it’s probably a mislabeled switch.
You can still fix it, but it may be some trial and error to find the right combination of where each wire should connect.
Just keep the wires labeled and keep track of the options you’ve tested, and you’ll soon have it installed correctly.
Upside-down switches are more of a nuisance than a serious problem. Still, in most cases, they are caused by the switch being wired incorrectly and can be fixed quickly.
On some rare occasions, it can be a bad dimmer, and you would need to replace it if you don’t like it being upside down, but many people choose to just live with it.
Have you ever had an upside-down light switch?
If so, how did you fix it?