You are here:

Electrical Wiring in the Home/hooking up a lutron 3 way dimmer switch


There is only 2 wires coming out of the wall but on the new switch there is 4 wires 2 red 1 black and 1 green how do I hook it up


Not sure I understand your question, are you trying to install a new 3 Way dimmer to an existing three way circuit at one end?

That is not possible,   

It takes three wires at both ends for a 3way circuit,  see below:

Now, are you simply asking how to use a three way dimming switch on a single switch circuit?

You can do that, but if you just purchased a three way dimmer for a single switch circuit,  and you can return it,   please do,    the three way switch is way more expensive than a single circuit switch,         

But if you are stuck with the three way switch,  and want to use it on a single circuit,   then you can use one of the reds    put a wire nut and tape off the other red,  then use black to black          colors dont really matter,      but to keep it simple    put one red from switch to white,    tape off the other red,     put the black switch lead to the black wire from the wall,      

Now the fourth is a ground   earth ground or frame ground,    somewhere there should be an earth ground in your existing box,   it might be the box is metal with metal conduit feeding it,  in that case the green from the switch can go to the box    there should be a screw or threads for a short screw   to attach the green switch lead to,

Below is a Lutron video  for a single pole install,   Lutron has this eco control function  where maybe more than one light is dimmed by one switch     

In that case refer to the beginning of the Lutron site and choose your switch from the examples and use the drop down menu to select if you have a three way or single pole or eco,    I think these videos will be helpful,   as again I am not clear what you had,  have, or are trying use,    it is OK to use a three way switch for a single circuit,   overkill   but maybe it was surplus or you just had it and want to use it on a NON THREE WAY CIRCUIT      

A three way circuit turns on a light or series of lights from TWO LOCATIONS<         a single pole dimmer can control multiple lights from one switch   but they will dim at the same rate,    sometimes this is confusing,      when there are multiple lights and one switch,   some assume that they need a three way switch,     not true,     if there are more than one light or multiple lights controlled FROM ONE SWITCH       all you need is a single pole dimmer,    now it will dim all the lights at once, not one at a time,    

Here is the beginning page of the Lutron site,     where you can select the swtich you are working with and then select the video you need for your install or replacement,   

Is it possible one of the wires from a three way has fallen back in and behind the box or someway has been pulled in out of sight in the box?

But you will need three wires for a three way circuit   one switch of the two is dimmable,   it gets tricky  but the basic configuration of a three way circuit  [two switches one at one location, one at the other that control the same light[s] is still the same,  one traveler wire is connected from switch to switch,  not to the load [light[s]].

Again if you are simply using a three way dimming switch but only have one switch total for one or more lights     then use it like a single pole switch,   and tape off one wire,   but also again,  if you only have one switch    then there is no need for the three way switch as it is much more costly than a single switch or single pole dimmer,      

take a look at the Lutron sight, and after watching the video from the example switches on the page,    write me back and give me the entire story of what is going on,   and what you have   [how many lights, how many switches to those lights, so on]  and we will figure it out from there  
About Electrical Wiring in the Home
This site answers questions related to home electrical wiring, home wiring, general electrical help,and other electrical questions related to aleternating current (AC). You can find help on the National Electical Code, home electrical issues, wiring electrical outlets, installing lighting, electrical grounding, and general electrical help for do-it-yourself projects not require an electrician. If you do not see your home electrical wiring question answered in this area then please ask your electrical wiring question here

Electrical Wiring in the Home

All Answers

Answers by Expert:

Ask Experts


Will Babbitt


Electrical issues of all types, wiring, control, appliances, components, specialty in Electric MOTOR or APPARATUS trouble shooting, electric motors, electrical problems, single phase, three phase, DC, capacitors, elevator MG-Sets, modifications, reverse engineering, VFD Drives, single to three phase convertors. Repair of most any electrical/mechanical/electronic apparatus, OEM, AC, DC, Industrial Applications, Three phase, single phase failure mode, determining the root cause of the equipment failure BEFORE failure repeats, Antique appliances, electric motors, fans, ceiling fans, base mount fans, poor equipment performance, Modifications, habitual failures, vibration, redesign, obsolete issues, collectible items restored, rewinding. Owner of EMR Repair Inc More information on electric motors, under Engineering/Motors Ask about any electrical or mechanical problems in the home, office, or even at your work. B2B or business to business CONSULTING I can do but it would be a much more complex issue, that would require a significant amount of time. from there we can discuss and begin work on about anything. Industrial electric motors, controls, troubleshooting, vibration, alignment, any type of industrial or commercial electric/electrcical equipment For the home owner, renter, apartment if you have odd things going on, describe to me, photos are normally very helpful, appliances, heating and air conditioning issues, light switches, installation, DIY PROJECTS FOR THOSE NOT EDUCATED IN ELECTRICAL, we can do some things, but for safety and sanity reasons, I may refer you to a local electrician, and help you find one, help you with pricing and even speak directly with anyone you hire if you have issues,


Over thirty years with a major repair and sales company, VP of Operations, and former owner of my own specialty repair shops, MEAR Services local to Kansas City Missouri EMR Repair Inc., located in Kansas City Missouri, 2014 sold both businesses to JCI Industries, Lee's Summit Missouri Evaluation and repair of electrical/mechanical apparatus. Electrical and mechanical repairs, trouble shooting including, vibration and balance issues. provides this service, and the huge costs to provide help on about any subject. They provide the servers, the people to vet the experts, costs that would be the same as operating a good sized business, They should be appreciated for what they do, the huge costs and the great help they provide for free, Electric motor questions, can be answered here but there is a dedicated category that has other experts to help and add to a solution. Other common questions, are noises in the walls, breakers tripping, devices not starting or shutting down for no apparent reason, smoke alarms buzzing, thermostat change outs, or sizing wire or needing information for a new project, but anything can be resolved, anything, with enough effort and patience, DIY, with electrical is possible, but in most cases the use of a simple ohm meter or volt meter is needed, they can be purchased at any hardware store for a few bucks. If you have smoke, or smell smoke, don't be writing me, call 911 the Fire Department has no problem looking for smoke smells, better then spraying water on a blazing fire. DO NOT GET CAUGHT INVESTIGATING AND TRAPPED IN A BASEMENT LOOKING FOR A BLOWER FAILING< As to the tip jar, it is up to you, it is appreciated, every expert spends out of pocket that I know, we spend on IP time, computer wear, printing documents, books, and of course our time, but if we prevent a $400 service call, we did well,

Former IBEW, EASA, IEEE, UL, ..............


10 plus years, various Technical Schools, followed by Industrial College Credit and non Credit Courses, electronics courses, experience in most any electrical apparatus, electric motors and generators, AC OR DC, fractional to above 5000HP, other electrical apparatus, slip rings, sleeve [plain] bearings, lubrication, identification-no data plate, control components, service and sales. I have continued night schools for decades, the list is extensive. I have been in the business of repairing most anything with wires or mechanical parts for decades, I have some helpful hints and directions you won't have to dig up. Or hopefully not have to pay a huge service call invoice to find.

Awards and Honors

Past/Present Clients
Federal Government, National Weather Service, NOAA, Commercial Power Plants, Major Vehicle Manufacturers, Printers, Other industrial and Commercial Businesses

©2016 All rights reserved.