Evaporative Swamp Cooler Switch Wiring

By | May 2, 2023

Evaporative Swamp Cooler Switch Thermostat Wiring 2020
The wiring of a swamp cooler is not complex, but if you have never wired up a motor before or feel uncomfortable with electricity, it is advisable to hire an electrician to wire up your cooler.

A swamp cooler needs power to run two things.

  • Blower Motor
  • Water Pump

The water pump is what pumps water up to the cooling pads and is almost always 110/120 volts AC, and like any 110/120-volt appliance, it simply needs to be plugged into work.
Swamp Cooler Switch Wiring Overview 7
It will operate like any 110/120-volt appliance once it is plugged/wired into a cooling unit.

A blower motor blows air into a building and can be either 110/120 volts AC or 220/230 volts AC, and can also have connections for low and high speeds.

Here is an example of the typical wiring of a swamp cooler switch. Wiring can change between different manufacturers.

Example Evaporative Swamp Cooler Switch Wiring Diagram

Be sure to always follow the schematics from the manufacturer for any motor or switch.
Swamp Cooler Switch Wiring Overview
The common (white) wires are usually all tied together in a wire nut.

Swamp cooler motors can be 1-Speed usually labeled only Low, and 2-Speed usually labeled both Low and High.

Here is a picture of a swamp cooler blower motor with the leads for Hi, Low, and Common labeled H, L, and C.
Evaporative Swamp Cooler motor hi lo wiring
When voltage is applied to the low side of the windings in the motor, it will turn the motor slower. When voltage is applied to the high side, the windings in the motor will turn it faster.

Common Evaporative Swamp Cooler Wiring Color Codes

  • Red = low
  • Yellow = Pump
  • Black = Hot Wire
  • White = Common Wire (Neutral)
  • Green = Ground Wire

The hot wire (black) goes through a switch to the motor.

The common wires (white) are all tied together to complete the circuit when the switch is flipped.

An evaporator switch is the most common way of controlling a swamp cooler, although thermostats can also be bought to control a cooler.

Single switches are also sometimes used with a single motor speed, and the pump is simply tied into the switch.
How to wire a evaporator switch
An evaporator cooler switch is a much better option since it can change from low to high speed as well as fan and pump only.

Example Swamp Cooler Switch Wiring Schematic.
Evaporative Swamp Cooler Switch Thermostat Wiring 2020

The above is a basic wiring schematic for a swamp cooler switch. (Always follow the schematics that come with the switch that is bought, this is only an example.)

On the left side is the wiring coming from a breaker with Black (hot), White (common), and Green (ground).

Ground: The Ground wire is connected to all the grounds with a wire nut.

Common: The common (neutral) wires, usually white, are all connected together, including the common side of the water pump.

Hot: The Black wire or hot side is connected to the switch and will give power to the proper setting when the switch is turned.
Here is an example of a 110/120-volt swamp cooler switch that is wired in.
Swamp Cooler Switch wired in

  • L1: The hot wire coming from a breaker.
  • 1: The Red wire is coming from low side of blower motor.
  • 2: The Yellow wire is going to hot side of water pump.
  • C: The Black wire is going to high side of blower motor.

The switch will have the low and high sides of the blower motor connected to it along with the hot side of the water pump.

As you can see from the simple diagram above, the only real worry to focus on is wiring the hot side correctly into the switch.

The hot wire is from the breaker and is usually a black wire. The white wire from a breaker is usually common.

The wires coming from the high and low sides of the motor need to be connected properly as well as the hot side from the water pump.
Basic Evaporator Switch wiring schematic.
Since the common wire (white wire) completes the connection, it does not need to run through the switch; the same with the ground (green) wire.
Evaporative Swamp Cooler wire color codes

Keep in mind that wiring color coding is not always followed. While it is supposed to be followed, Black (hot), White (Common), it is always a good idea to double check. Especially in older homes where the wiring may not have been done correctly.

If you are replacing a switch or doing a new install from scratch yourself, this will not be a problem, as you will be able to spot if the wrong wire color coding is being used.

Where Can a Swamp Cooler Switch be Bought?

Swamp cooler switches can be bought at any hardware store or online at Amazon or eBay.

If you have an old broken switch, it is usually best to match it to the same or similar replacement switch, which will make installation easier.


Category: HVAC how to

About Aaron H. Benetti

Aaron H. Benetti an HVAC technician who has worked in the field since 1991. He began his career as an HVAC installer and later began doing troubleshooting and repairs. Around 2010, he began to write books on HVAC topics, mainly tutorials and how-to information. Currently, Aaron works as an HVAC tech and also writes many articles and posts for websites as well as books and videos on HVAC topics.

31 thoughts on “Evaporative Swamp Cooler Switch Wiring

  1. dave

    I have 4 wires coming from the roof down into my two speed cooler switch, a white, red, green and blue. It is a MasterCool evaporative cooler. On my switch which wire goes where? L1, 1, 2 and C

  2. Ari

    HI I’m trying to switch my swamp cooler switch to an electronic control switch. Mine looks just like the diagram above. The new electronic control switch has a 5 wires. The extra wire is a white control wire. Where does this go? Or can I just cap it off? Thanks

  3. Joseph Smith

    Most of these questioners should stay the heck away from their machines! Your either gonna electrocute yourself or burn your house down! Smarten up…..for a few bucks, hire a pro!…..how do you all SLEEP at nite?…..JEEZ!

  4. KJCNM

    Thanks your picture is the closest to what I’m trying to do except for the “L1”. But I have to say thanks anyway.

  5. Cesar u

    I’m trying to hook a 2 speed 120 motor,my problem I have two blacks and 1 green coming out of roof.when I test 2 blacks it’s shows me 220 and then I test 1 black to green its shows 120 same with other black do have 220 or 120 .when I hook the black and green it run but heats the motor and shutdown

    1. Emmanuel

      Sounds like the 2 black wires are for 220 volt motor and your wiring in a 120 volt motor. Cap off one of the black wires and only use 1 black wire which should be 120 volt. Double check with a meter.

  6. Chad

    I replaced my cooler and wired it the same as the old. When the switch is on high it blows like it’s on low. When its on Low it barely blows anything at all. The cooler is an identical replacement with same size pullies and blower. I have 115v to high when on high and 23v to low side. When on Low I also have 115v with 23v to high side. I’m stumped as to why it turns so slow.

  7. joaquin

    I have a white and green wire. Understand they tie in . But which is best to tie them to

    1. Jose Ventura

      White is common and Green is ground. Green will go to a metal ground while all the white wires tie into together with a wire nut.

  8. Denise L Mc McDonnell

    my swamp cooler wont turn on at start if someone is on the roof and kickstarts the belt it runs would this be the belt tension maybe the windings or somehow the pulley or is it the motor ….any takers ?

    1. Darrell Day

      It’s probably the moter switch, when they go out the moter isn’t being sent the right amprage to start.Thats why it starts with a tug on the fanbelt, and won’t work at all on low speed.Its either on the front of the cooler or the wall.Iam having the same problem and the moter is new.Buying a new moter switch.If your moter is real old it could mean your moter is bad and tired.Your moter switch relays high and low amprage. Thank You I’ll be here all week 😉

  9. Tonya Sherwood

    Someone connected a light switch for the swamp cooler instead of a swamp cooler switch. I’m trying to put a swamp cooler switch in so I can use high and low as well as the pump instead of just high cool. The problem is I have 4 wires running from the switch to the electrical box in the swamp cooler vent and 5 wires going from that to the swamp cooler itself. Do I run another wire or is there 2 wires that can be connected to one wire in the switch?

    1. Tubby Grey

      Since this question is eight months old.. Hope your question has already been resolved..
      The motor plug is made for both 120 and 240 voltage.. you’ll need that fifth wire only if you have 240 voltage.. if that’s the case, Google manufacturer’s website and look for the wiring diagram of the model number.. If you have 120 voltage twist a wire nut on the unused wire..

  10. Ginny Andersen

    Hi I have a swamp cooler with a Dial 7634 Thermostat. I can turn on stat to fan only & it turns fan on. When I put it on Cool nothing works ?

  11. Dan

    Hi. i have a typical Hi, Low, Pump swamp cooler control and 2 speed motor (120 volts). i am taking a dedicated circuit to the control switch now but discovered previous install put the Neutral wire through the control switch. i can see how the pump could run with reverse polarity but would the motor actually work as it should? it runs all functions correctly according to operation of the Standard selector switch. would it be just as simple as taking the new Hot (Black) to L1 on selector switch and the new Common (White Neutral) to the wire nutted connection bundle in the switch box? in other words, Hot apparently goes to C terminal on the motor and the Hi, Low, Pump functions are run by the Neutral via the selector switch. Please advise. Thanks Dan

    1. Cathy

      Heres my question: i have champion 3000 replacing with a 3000.
      The switch on old one has the metal prongs on the back where you slide the disconnectors onto them instead of a switch with screws. So in old switch they have red ( where your red is) motor black where your pump yellow is then they skip one and put purple pump where your motor black is. With hot wire for power where your hot wire is on l1.

      Is it just a different wiring schematic?

  12. Ed Feist

    I have a Honeywell thermostat RTH7600D that currently operates my furnace. I have a White-Rodgers 8A18Z-2 controller on my evaporative cooler. I have been using a White -Rodgers thermostat to control the cooler but would like to use the Honeywell to control BOTH heat and cooling. How should I do the connection? Just R to R, W to W, Y to Y, and G to G or something special? Thank you.

  13. Tim

    Hello. Tanks for the information. I have a strange problem. After working fine for a month, my evap cooler will only run on high. When switched to low cool or low vent , the cooler stays on high. Is this likely the wall switch or the cooler motor. Thanks for the help.

    1. Thomas

      Sounds like the stitch may be shorting. Probably best to replace it.

  14. Lisa

    Need a picture or skamatics for a mastercool plus tekelek 3-1091-2 thermastat

  15. Lannea Rae

    I have the three wires coming from the pump and four wires coming from the motor which means, I think, that I have an extra wire for the pump, orange. Am I hooking up both the black wire directly from the pump and the orange wire from the motor in the same spot that you have the yellow wire.

  16. Charlie

    I have the same switch and the low and high cool settings are reversed* – is that just wires 1 & C reversed? Thank you for posting this!

    * It blows low on the high setting and vice versa.

  17. Hyber

    My Master Cool water pump does not work. I’ve recently replaced the pump and I know it works when I plug it into a standard outlet and when I engage the test button it works but it won’t work with the installed system. I’ve metered the wires and I’m only getting 20 volts to the pump but the pump still turns on with the meter. The thermostat has good voltage of 24 volts. I suspect the controller now. Thoughts?

    Also, when I metered the fan, it turned on and now I can’t get it to shut off, any suggestions?


    My swamp cooler only runs the pump on low cool. The high cool only speeds up the fan, the pump stops. Any advice?

  19. Felix B

    Thank you for posting this. If I was going to use my cooler this past summer I needed to learn how to install a new/different switch. Your posts mention of connecting the commons to complete the circuit when the switch is engaged was that missing piece I needed to complete my task. You rock.

  20. Jacob Ray Stephenson

    Where does my yellow wire go into my motor?? Theirs no spot for it

  21. Todd

    Replaced swamp cooler. When I turn on pump blower runs for one min then stops. Triple checked schematics all good. Could the breaker be an issue?

  22. Eric Rose

    Question. My evap motor runs at either 1725 rpm or 1140 rpm. This house has an old single speed switch. The hook up runs fine but I can’t tell if it is running at the hi speed setting. I reversed the black hi speed and the red low speed connections marked H and L on the motor and I still can’t tell the difference. If I disconnect the red wire only, the motor stops. How do I wire it for Hi speed only?

  23. Teresa Kennedy Harris

    I have a question, my cooler has stopped working on the high setting. We switched out the motor and now we switched out the switch. Still won’t work on the high setting. What could it be? It won’t work on high cool or high vent.


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