Evaporative Swamp Cooler Switch Thermostat Wiring

By | June 21, 2019

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.
Motors and switches wiring can change from different manufactures. Be sure to always follow the schematics from the manufacture for any motor or switch.
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 in to work.

It will run like any 120 volt appliance once it is plugged/wired into a cooling unit.

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

Here is 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 than the windings in the motor would turn the motor slower, when voltage is applied to the high side than the windings in the motor will turn it faster.
While the hot wire (black wire) goes through a switch to the motor, the common wires (white) are all tied together to complete the circuit when the switch is flipped.
A evaporator switch is the most common way of controlling a swamp cooler, although thermostats can also be bought to control a cooler.
A Evaporator Switch
How to wire a evaporator switch
Basic Evaporator Switch wiring schematic.
Basic Evaporator Switch wiring schematic.
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 simply connected to all the grounds with a wire nut.
Common: The common 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 120 volt swamp cooler switch that is wired in.
L1: This is the hot wire (Black) coming from a breaker.
1: Red wire coming from low side of blower motor.
2: Yellow wire going to hot side of water pump.
C: Black wire going to high side of blower motor.
Swamp Cooler Switch wired in
The switch will have the low and high side from 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 (black wire on the bottom in the picture) correctly into the switch. The wires coming from the hi and low side of the motor need to be connected properly as well as the hot side from the water pump.
Since the common wire (white wire) simply 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 simply because wiring color coding 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 usually be bought at any hardware store. They can also be bought online at Amazon or eBay.
Swamp Cooler Switch On Amazon
LASCO 36-0233 Evaporative Water Cooler Thermostat with Two Speed Six Position Switch


20 thoughts on “Evaporative Swamp Cooler Switch Thermostat Wiring

  1. 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

  2. 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.

  3. 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 mother 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 😉

  4. 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.

  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

  6. 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.

  7. 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

  8. Lisa

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

  9. 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?

  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 ?


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

  12. joaquin

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

  13. 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.

    1. Aaron Benetti Post author

      There must be a broken connection with the wire somewhere between the switch and the high side of the motor. Most likley it is in the junction box in the cooler with the wire nut, but could possibly be a cut wire also. Don’t leave it set on high until you find it since it could short out. Let us know what you find.

  14. 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.

  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.

    1. Aaron Benetti Post author

      Most all water pumps are 120 volts the same as a household appliance. One wire will tie in with the others (common), and the other wire (Hot) will go to the cooler switch that completes the connection. The third wire on the pump will be ground. Be sure to look at the schematic.


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