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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 22013
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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HVAC Expert: we have two similar homes, similar size, on the

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HVAC Expert: we have two similar homes, similar size, on the same property in the midwest great lakes area. Four seasons climate, frequently humid in the summer. Both homes have older 80% forced air furnaces with central air conditioning units probably the same age. We have them maintained, and everything works fine. But I think at one point, someone complained about air-conditioning performance in the one house, so the technician turned the fan speed up when in air-conditioning mode at that house. So that house cools down very fast, excessively fast perhaps, but does not dehumidify well at all. -- The other house, it's kind of the opposite, the fan speed in air-conditioning mode seems very low, but it dehumidifies fantastic. In our area, comfort is primarily tied to humidity, since we don't see that many days in the 90s, and never 100F. I was planning to have the technician turn the fan speed back down in air-conditioning mode, so the one house dehumidifies better. Or maybe I can make this adjustment myself. But before we do, are there any other considerations that might affect how a forced air central air conditioning system dehumidifies besides fan speed? Additionally, nothing has changed with the system in question, it's been like this for several years, I'm just finally deciding to try and improve it. Thank you

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

You have a ood understanding of the principles involved and yes reducing the fan speed in this case would likely solve the problem. If you are comfortable pulling the blower swapping a blower motor lead you can do this yourself

If you want specific input on which leads to swap I'll need the brand and model number of your unit

Customer: replied 4 months ago.
Thanks Rick. Here is the Bryant label with product information. The diagnostic red light is solid, not blinking. I did not yet turn off the power, and I have not removed the lower door to access the Circuit board and blower area yet. If there is any sequence or important steps to this, please let me know as it's definitely not my area of expertise. :-)

Just kill the power to the unit then refer to the wiring diagram (should be pasted to the back of the blower compartment access panel which should call out the speeds (by lead color) of the several leads from the blower motor. Just swap the next lower speed lead for the one now on the AC fan terminal on the board. And move the one that's currently connected to the parked (unused) terminal the other lead was connected to.

Customer: replied 4 months ago.
Hopefully I can figure this out. But first, it appears a tech has defeated the blower compartment safety switch, perhaps for testing it. I did cut the power, but we don't want that switch defeated do we?

It's not a big deal. It's there to kill the power when that panel is removed so the blower can't run with someone's fingers nearby. Pretty safe bet you won't put your fingers in there with the power on.

Customer: replied 4 months ago.
Ok. I believe this is the section of the circuitboard we want to be working on correct? See photo. And I will add on some gratuity for the extended help.

Exactly and with the color/speeds called out it should be a snap to swap them with the unused leads on the "SPARE" terminals.

Customer: replied 4 months ago.
Took me a minute to find everything, partially because the actual board is rotated 90° from the orientation of the diagram. -- anyway, the current arrangement appears to be the stock set up shown in the diagram. Cooling is black, high blower speed. Heat is medium low, blue wire. The Red wire, low speed, is parked. And those are the only three options, high, medium low, and low. -- I don't think we want heat on low. So we can either we've heat on medium low, and switch cooling from high to low. Or I can put heating on high, and have a choice of medium low or low to experiment with on cooling. What do you suggest trying first? Thanks

You probably don't want heat on high. Heat is usually low or medium low. I also would not put the AC on low since you risk the coil freezing up if the air circulation is too low. You might want to check that other unit that's working right but if need to make a decision now I'd put the AC on med lo and the heat on low.

Customer: replied 4 months ago.
I will check the other one. Are these wide plugs we are discussing (see photo) intended to be pulled out with my fingers, or do I need to grab the back of them with some needle nose pliers for example? -- also, what would be the problem with having heat on high in a primarily heating climate like Michigan? Thx

Usually needle nose make job easier particularly in tight spaces. The biggest draw back to heat on high is it makes the circulation drafty which can reduce comfort.

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Customer: replied 4 months ago.
I can't get the other furnace apart easily, so I will put cooling on medium low for now, since we have a few months of cooling season ahead. And heat on low. If that proves to be in adequate for heat later, I will just switch them around again for the heating season. -- my seat of the pants feeling is that medium low for cooling is still fairly strong. I would like to try cooling on low, but no your concerns about the coil not getting enough air flow. Thanks for all the help today Rick

You're welcome

Customer: replied 4 months ago.
The system didn't let me add a gratuity on my cell phone app, but I just logged into the website, and was able to add the tip there. I have no idea what % JA passes through to experts, but can you confirm that you received something extra, so I know it was successful. Thanks.

Thank for the tip, yes I did get it