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Forced air furnace, new problem: recirculating fan working but slow [pics]

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Forced air furnace, new problem: recirculating fan working but slow [pics]

Old 01-21-2018, 06:55 PM
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Default Forced air furnace, new problem: recirculating fan working but slow [pics]

Hey guys,

Thanks for the responses to my previous issue of the forced air furnace intermittently shutting off. Since getting the ducts cleaned (including the exhaust duct) it has not shut down inadvertently.

Here is the old thread:
Forced air furnace electrical question [pic]

So its rolling along, and now it has a new odd problem. Today in the middle of the afternoon, for no reason at all ... my parents said that there is a smell coming from the vents and the heat was only trickling in. So when I looked at it, I have the fan motor and the capacitor a smack as I always do whenever I see an electric motor issue.

The large recirculating fan that pulls cool air from inside the house, heats it up and pushes it around is working, doesn't appear to be "laboring" but it is no near as fast as it was before. Are these fans known to go bad? Furnace is somewhere between 8-12 years old.

I figure the control module is commanding the recirculation fan to turn on because I can hear a relay click just before the fan motor starts. So I figure that verifies the electronic controls, relay, wiring.

I'm going to replace the capacitor (easy and prob cheap).

Anyone know why there are so many wires going to this fan motor? (White, red, blue, yellow, black)

American Standard Freedom 80 2 Stage,
model AUD080R936K0
Serial Z5113MJ1G | LIne L1

Base of the re circulation motor with the starting capacitor
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Wires coming from the re circulation motor
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The gas valve and exhaust fan motor
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Relays on the control board that control the re circulation motor
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Starting capacitor
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The computer control board
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Old 01-21-2018, 07:53 PM
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You might want to make sure the batteries are good in your CO detector


And call someone in that knows WTF is going on with this.
Old 01-21-2018, 10:14 PM
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Originally Posted by Eastport205 View Post
You might want to make sure the batteries are good in your CO detector


And call someone in that knows WTF is going on with this.
Thx, got two CO detectors in that room.

I literally can't find anybody around here. I think its the computer controls that throw them off.

I called twice to get this thing fixed before, the first guy replaced a few parts but didn't fix it. Decided to try someone else, the next guy blew up / shorted the computer module (my mother said something went SPARK, then everything went dead), charged my mother for a new computer module which of course didn't fix anything.

The computer module controls the recirculating fan.
Old 01-21-2018, 10:54 PM
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Couple things.

All the electrical taped wires must have a story to tell. Is that a transformers all covered in tape??

The fan may be multi speed. Each additional conductor pulls in more or less poles to change motor speed. Like a turntable. You may have fried the high speed set (all poles) and are running on either Med or Low. Is the unit variable speed? Do you have selectable speeds somewhere?

Do you have a schematic?
Old 01-22-2018, 02:24 AM
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[QUOTE=makonnen;11039939]

So its rolling along, and now it has a new odd problem. Today in the middle of the afternoon, for no reason at all ... my parents said that there is a smell coming from the vents and the heat was only trickling in. That's not an odd problem


The large recirculating fan that pulls cool air from inside the house, heats it up and pushes it around is working, doesn't appear to be "laboring" but it is no near as fast as it was before. Are these fans known to go bad? yes

I figure the control module is commanding the recirculation fan to turn on because I can hear a relay click just before the fan motor starts. So I figure that verifies the electronic controls, relay, wiring. That sounds reasonable. There's several relays on the board though, they click at different times.

I'm going to replace the capacitor (easy and prob cheap). True, and it might fix your problem

Anyone know why there are so many wires going to this fan motor? (White, red, blue, yellow, black) yes



Originally Posted by Eastport205 View Post
You might want to make sure the batteries are good in your CO detector very good advice


And call someone in that knows WTF is going on with this.
more good advice

Originally Posted by makonnen View Post
Thx, got two CO detectors in that room.

I literally can't find anybody around here. I think its the computer controls that throw them off. That is sad

I called twice to get this thing fixed before, the first guy replaced a few parts but didn't fix it. Decided to try someone else, the next guy blew up / shorted the computer module (my mother said something went SPARK, then everything went dead), charged my mother for a new computer module which of course didn't fix anything.

The computer module controls the recirculating fan.
As far as forced air furnaces, they don't get any simpler than yours.
Old 01-22-2018, 05:47 AM
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Originally Posted by Eastport205 View Post
You might want to make sure the batteries are good in your CO detector


And call someone in that knows WTF is going on with this.
too true; nice wiring job, I would recommend a bigger hammer to get the motor turning.

Seriously replace both the capacitor and blower motor and fix the wiring. And make sure you have good quality CO detectors.
Old 01-22-2018, 07:48 PM
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Thanks guys,

Wiring is like that from factory, no one touched the wiring going to and from the motor.

I asked around my work place and got some recommendations on someone to call. Mind you, that is how I got the last two guys who turned out to be a flop.

I dont think these plumbing / heating techs are trained to deal with the computer controls that these newer furnaces are coming out with. As I mentioned, I'm a bit gun shy as the last two techs not only didn't fix it, but one guy even burned out the control module.

So I called a local guy, one man show. Report back tomorrow.
Old 01-22-2018, 08:21 PM
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I have a 21 year old, olf gas pack and experienced a similar problem. I had replaced the fan limit switch and the unit was humming along for a few weeks. I got through the first freeze. Then I started smelling a faint sort of plastic burn smell. I can hear when the gas exhaust blower kicks on and noticed the air circ blower was not coming on.

I tried the cap at first. Then followed some youtube tutorials for testing the motor and consulted the original installation company. The guy has been very helpful. Apparently 20 years is a healthy life span for a blower motor.

there is plenty of info about all the wires. white is common. Obviously the two browns connect to the cap. The other wires are speeds. My original motor, which is rare and at least 2 weeks away, was a 2 speed. A local house sold me a "truck" motor which had very close rpm specs and was 4 speeds and came with recommendations for which wires to connect when replacing it for a 2 speed motor. Higher speeds for a/c. Slower for heat.

the computer module controls more than just the recirc motor. It starts the blower, verifies the pressure (as you know from your previous thread), heats the igniter, verify's flame and maybe (I'm not a pro) controls your fan on off cycles depending on heat sensed inside the transfer "chamber" thingy.

there are quite a few key details about finding a replacement motor. Motor diameter, shaft size, phase, voltage, rpm's and the aforementioned speeds.

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