Author Topic: AC Blower Wiring Questions  (Read 16504 times)

Offline billnc

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AC Blower Wiring Questions
« on: June 16, 2008, 09:56:08 PM »
Oh the trouble that happens when money is tight.

I have a Trane gas pack and the indoor blower motor stopped working.  I had a prepaid service call in my pocket from my local HVAC guy.  He came out and determined that the indoor blower motor was fried.  I saw the capacitor reading ok, so I had confidence that he was telling me the truth.

It was to cost $410 to replace the blower motor.  About the going rate, but I simply didn't have it.

I knew where the local Trane parts dealer was, so I got the proper numbers and came home with the right motor.

I got the old motor out, got the new motor in, but here is where the plot thickens.

The old motor had 5 wires.  These included
#1 A ground wire
#2 A purple wire going to the capacitor
#3 A brown wire going to the other terminal of the capacitor
#4 A red wire going to a 4 post terminal of some sort where 3 other wires are attached.
#5 A black wire which was taped off & not attached.

As best I can tell the red & black wires were for fan speed choices. The schematic showed that either the red or the black could be attached to the terminal.

The new motor has 8 wires.  These include
#1 A ground wire
#2 & #3 - two same color wires which are to go to the capacitor
#4 thu #7 - Red, black, yellow, blue wires which are various speed wires
#8 A White Common wire

I was guessing to attach the black wire (High speed) to the post where the former red wire was attached.

I have no idea where to attach the White common wire.  The old motor didn't have one.

I can't get the thing to work and I know my HVAC guy will STILL want $400, even though I've already bought the new $100 motor.

In fooling around with the wiring, the unit clicked once, and now there doesn't seem to be any power available at all.  I can't find a tripped circuit breaker & I didn't know whether or not there was some internal fuse that I've blown & what it would look like.  And again, I don't know where to connect the White common wire.

Any help would be greatly, greatly appreciated.

Thanks so much, in advance.

- Bill

Trane - YCC024A1LOBA

Offline RegUS_PatOff

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Re: AC Blower Wiring Questions
« Reply #1 on: June 17, 2008, 09:39:04 AM »
something is missing on your old motor wiring numbers.

There needs to be another connection to the voltage, common...
Do you have some part numbers from both motors ?
« Last Edit: June 17, 2008, 08:42:52 PM by RegUS_PatOff »
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Offline JWWebster

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Re: AC Blower Wiring Questions
« Reply #2 on: June 17, 2008, 04:11:34 PM »
 EDIT: Earlier I read your question wrong. I was thinking this was a condenser motor. Your question about the white wire really is simple. The new motor has two brown wires going to the capacitor. One of those brown wires has a white stripe on it. It is the same as the purple wire. Put it on the capacitor on the terminals marked COMMON. The other brown wire goes to the capacitor terminal marked FAN. Hook red and red green to ground(chasis) tape off all the other wires from each other and the ground.
« Last Edit: June 17, 2008, 07:53:52 PM by JWWebster »
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Offline Repair-man

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Re: AC Blower Wiring Questions
« Reply #3 on: June 17, 2008, 06:15:25 PM »
There's no contactor.

More than likely, your friendly AC guy snipped and taped the wires, particularly the black hi-speed wire, since he said the motor had "fried". My contention is that the black wire at one time also went to one side of the relay where the red heater speed wire is connected. Usually this is a standard 90-340 relay.

Wire as follows:

Black to the n/o terminal on the fan relay (see furnace diagram on door)
White to any white common connection on the furnace (transformer i.e.) if this is a Gas furnace. Otherwise the white wire goes to L2 if this is a 240 volt electric air handler.
Red to n/c terminal on the relay. The low speed is powered thru a separate fan/limit control, but connects at the same relay as the black.

The 2 brown wires naturally go to the capacitor terminals, and it does not matter which one goes where, just match the new capacitor rating to what is called for on the new motor box, as different motors usually take different run caps. Tape the other leads (yellow, blue, etc. out of the way)
« Last Edit: June 17, 2008, 06:25:24 PM by Repair-man »
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Offline JWWebster

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Re: AC Blower Wiring Questions
« Reply #4 on: June 17, 2008, 07:40:55 PM »
The new motor has 2 brown wires that go to the capacitor. One of them wires has a white stripe on it. That brown wire with the white stripe is the same as your old motor's purple wire. tape off the white wire and disregard it. Connect the red wire where the old motors red wire was . bolt the green ground wire to the frame. The brown wire without a white stripe goes to the capacitor terminal marked "FAN" Tape off any remaining speed wires so they will not short out against each other or the frame.
« Last Edit: June 17, 2008, 07:44:58 PM by JWWebster »
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Offline billnc

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Re: AC Blower Wiring Questions
« Reply #5 on: June 17, 2008, 11:55:32 PM »
WOW!

Great answers.  I stayed up most of the night last night trying to research the 'net to figure out what to do.

Like here, I found many potential answers. 

I decided to go with the simplest set-up first and see what would work.

The brown wires are both completely brown, no white stripe.

I retested the fuses, which I suspected I had blown in my first wiring attempt.
They were good when the repair guy was there, because the compressor was
running.

The fact that I miswired on my first attempt is why they say "Don't try this at home." 
I prayed that I hadn't REALLY fried my complete system (and thankful that I hadn't
fried myself.)

I had, in fact, blown both fuses.  I replaced them.

I connected the black high speed fan wire to the fan relay.

I screwed the green ground wire to the frame.

I connected the two brown wires to the capacitor.

Yes, I replaced the capacitor & yes, I made sure it was
rated for the motor.

There had been a blue wire attached to one of the posts
on the capacitor going off elsewhere into the system.  I reattached
that blue wire.

I taped off the remaining speed wires.

I taped off and DID NOT connect the white wire to anything.

I inserted the power cutoff and heard the most beautiful hum in
the world.  The motor was whirring away.

My guess is that the blue wire coming off of the capacitor is acting
as the common - return for the motor. 

It has run fine since this afternoon.

I am really, really grateful y'all took the time to reply.

Thanks again.

- Bill

Offline JWWebster

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Re: AC Blower Wiring Questions
« Reply #6 on: June 18, 2008, 11:43:13 PM »
Well if both brown wires were the same then White is the same as purple. Glad to see you have it going.
May the hinges of our friendship
        never grow rusty.

About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
I love fan letters! LOL

 

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