I have a Carrier 59SC2C100S211120 furnace. The blower is pretty loud and everyone says they really feel it when it comes on. I would like to turn down the blower in normal operation and then, if also possible, make it very low in "on" mode (may eventually buy new thermostat with circulate mode instead).

I've read that you can adjust certain wires to get different fan speeds. So far, I've found the owner's manual(s) which all say something like:

On all but the base series furnace, the blower speed can be increased or decreased if desired due to change of seasons, large gatherings in your home, etc. Simply change your FAN from ON to OFF for 1 to 3 seconds (or AUTO depending on your thermostat), and then return to ON. The blower will switch to the next higher speed. There are at least three speeds to choose from. If the blower is running on its highest speed, a request to change will direct the blower to return to its lowest speed.

I normally have it on auto. I set it to on for a few seconds then switched it to auto and back to on and I couldn't really tell a difference. Is this actually a real thing or something that just doesn't apply to my system?

I would love to play around with just the push of a button or if this can be manually controlled in the Tech Menu (Thermostat on this system is TP-P-705)? When I moved in (new build) they specifically told me it was a single speed so I've never really tried anything before

Also unclear if there is a way to make this a multi-stage (?) / "smart" blower - e.g., when there is a lot of temperature to make up go faster as needed or ramp up/down? If this is possible with some accessory or better thermostat, I would consider this.

Does this actually work? If not, would appreciate guidance on what to do with the wiring. Will also try to find the actual full manual as well.


photo of controller board

1 Answer 1


Unfortunately you do not have the "Automatic Fan speed control"

However you can still change the Fan speed by charging the Fan Motor wiring.

Obviously you would Turn Off the power and verify it is Off with multimeter or Non Contact tester.

Open the panel to access the control board.

You will see bunch of different colors wires going to the Fan motor.

Note which one is connected. Take a pic.

Now choose your Fan speed and connect the assoicate wire according to the Table.

fan speed

If you need more information you can find it here for your model. Suggest you download the Manual for future use.

User manual


How to remove the connection.

Gently pull the black lip away from the plug (do not break it). Pull the plug upwards.


  • thank you, i will start by taking a photo with the power off. I assume I will be looking for it to be labeled "cool" and "heat". In the table you posted, I am the second line, "92%", correct? Will also go and read the manual.
    – HelpEric
    Commented Sep 8, 2022 at 3:41
  • As a follow up, I could also foreseeably get a variable speed motor that is compatible with the system? I am surprised there isn't some type of device that could work like a switch/toggle or emulate the difference based on measuring some other input.
    – HelpEric
    Commented Sep 8, 2022 at 3:44
  • 1
    @HelpEric I wish they would instal a switch at least, but the philosophy is you do not use it often, if at all. At least they put multiple speed motors. Yes, you would be 92%. You can not miss the fan motor, then just follow the wires
    – Traveler
    Commented Sep 8, 2022 at 4:12
  • thank you. Before changing anything, I want to attach photo to my original question and confirm - To me it looks like currently cool==black wire == hi speed. So if I were to switch the heat and cool at the bottom left corner then I should expect it to be less loud and I could switch these when the season change again if I feel the heat is too loud? This should be less risky then going yellow which is med low as that might not be fast enough and could cause a problem with overheating from insufficient speed?
    – HelpEric
    Commented Sep 8, 2022 at 14:02
  • 1
    @HelpEric They are pull up straight. BUT sometimes like in your case there is a small plastic flap (on the left) that holds them in place. Very gently push the plastic flap away and pull the plug up, you might have to wiggle it bit to come out.
    – Traveler
    Commented Sep 8, 2022 at 20:03

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