Blower not running in A/C mode

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  #1  
Old 05-16-18, 05:30 PM
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Blower not running in A/C mode

I have a old magic chef ac/furnace. New cap and blower motor. If i use the heat the blower motor works like normal. But when I try my ac, you can hear the transformer hum and a loud click from the relay. Also the just the fan option at t stat does not work either.
 
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Old 05-16-18, 06:35 PM
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The first thing that come to mind...

The DPDT relay on the fan center requires relacement.

The fan works in heat mode because the fan limit controls blower operation in heat mode.

Post some picture of the furnace control board or fan center so we have a better idea of what you have.
 
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Old 05-16-18, 07:11 PM
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Welcome and a little help with pictures.... -How-to-insert-pictures
 
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Old 05-16-18, 07:12 PM
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Here's the picture of what you asked for. Thanks
 
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Old 05-16-18, 07:15 PM
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Thanks for pic info. And thank you for your assiatance
 
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Old 05-16-18, 07:23 PM
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That's a basic fan center. The square black box is the relay.
The red, black and blue wires are the fan speed wires.

Turn the power off. Loosen the two screws holding that plate on.
Turn it over and post a picture of the back.
We need to have you check if it's a relay problem or a motor winding problem.
 
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Old 05-16-18, 07:25 PM
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Wow, maybe I should pick up a lottery ticket...

That is an odd relay on your fan center.

Probably going to need to replace the whole fan center after proving that it is the relay.
 
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Old 05-16-18, 07:30 PM
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The relay is rivited to the black box. All u can see are the wires soldered onto it. It's a 83 model
 
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Old 05-16-18, 07:34 PM
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Where would I get one like that?
I can pop off the rivits and take pics if that will help
 
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Old 05-16-18, 07:54 PM
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The relay is riveted to the plate. The plate and relay come off together.
Look for the two straight screws.... one is visible in the picture.

OH..... you have the plate off. Post a picture of the wiring there.
 
  #11  
Old 05-16-18, 07:58 PM
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Here's pic of the relay with the cover off
Is this what you wanted a picture of?
 
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Old 05-16-18, 08:53 PM
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This is the exact replacement for that fan center.
Oem-factory-replacement-fan-control-center-relay-transformer-armstrong-magic-chef

I'm trying to find the wiring diagram for that relay. There is a pair of red wires and a pair of black wires. One is normally closed and one is normally open. The normally closed pair is the furnace. The normally open pair is the A/C blower. I don't want you to change the relay if the A/C speed on the motor is bad. If you can determine from the wiring diagram.... just short the normally open pair. If the blower works... the relay is bad.
 
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Old 05-16-18, 09:13 PM
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When you say motor, what motor are you referring too?
And I do not have a wiring diagram of the relay. There is a wiring diagram on one of the front panels but is simple one. No color code for wires
 
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Old 05-16-18, 09:53 PM
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I was wrong it has wife colors on it
 
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Old 05-17-18, 06:05 PM
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Excellent pics of the diagrams.

Short out the black pair of wires on the relay. Be careful as this is 120vac.
If the blower runs on high speed.... the relay is bad.

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Old 05-17-18, 08:45 PM
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If the fan runs when you connect the 2 black wires to your relay you can pick up a Mars 24010 DPDT fan center for $35 on Amazon.


 

Last edited by Houston204; 05-18-18 at 05:52 AM.
  #17  
Old 05-18-18, 05:28 AM
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These are the connections that I would make when installing that $35 fan center.
I would number the existing wires with a sharpie or tape and a sharpie and then snap a few pictures before replacement.



Have you tested the old one yet?
It kinda needs to be replaced either way at this point.
 
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