AC woes, starting to warm up...


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Old 07-01-08, 07:50 PM
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AC woes, starting to warm up...

Problem with AC

We had a power outage a while back and now my ac is flakey. This outage killed the relay on my fridge, so it wasn't pretty.
At first, the blower motor would not shut off after the house had cooled to the desired temp.
As I was trying to track down the blower problem, we developed the problem of the outside compressor running, but the blower would not kick in. (I didn’t run it long like this.)
I couldn’t even get the blower to run with the “ON” switch from the thermostat.

So, I did what any good DIYer would do in this situation, I replaced a part w/o knowing if it would help the problem.  I put in a new fan control board. That fixed some things, but not everything.
So now, I have the heat/cool on the thermostat off, and the fan on “auto”. When I go down to the furnace, I can hear the blower motor humming.
When I put the thermostat heat/cool off but the fan on “ON” the fan starts up like I’d expect.
When the thermostat is put in Cool, the blower motor starts up, but the outside compressor does not go.

I just checked the outside disconnect, the fuses are good.

I have a Tempstar furnace model N9MP2. This worked 1w/o incident earlier this year.
The thermostat is a white-rodgers programmable, model 1f80-261 B

What can I check now?

Any suggestions are appreciated. Have multimeter, will travel (up and down stairs, untill this is fixed)
 
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Old 07-01-08, 08:59 PM
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replace the capacitor in the outside unit and you should be good to go.
 
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Old 07-02-08, 06:08 AM
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I'll do that: replace the outside cap.

However, I'm still concerned about the humming sounds I get from the inside blower motor when the heat/cool is "off" and the fan is set to "auto".
Seems to me there shouldn't be anything going on at that point.
Granted, there are two transformers in the furnace cabinet.
 
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Old 07-06-08, 06:59 PM
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So I go to size my Cap to see what I need to pick up, and I figure I might as well double check that power is getting to the outside unit.
Turns out, it's the relay. I'm getting 220 on one side and nothing on the other. I used the lead on the meter to depress the relay, and my compressor starts right up.

Turns out the relay had died on my fridge earlier, stupid power surges.



The humming noises are loose covers on the transformers and heater control.
 
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Old 07-07-08, 05:23 AM
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So I wake up and have a "duh" moment.

The 240 does not activate the relay, the low-voltage wires do.
Took me a night's rest to chew on that one.

So, I guess I'd better check that the wires have continuity, and that they are attached at the correct spots.


Is there a compelling reason to use solid copper wires vs stranded copper?
 
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Old 07-08-08, 05:32 AM
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Problem was wire from AC contactor had come loose before I replaced the board. I saw a loose white colored wire and just assumed it belonged on a terminal marked "W".

After checking voltages and looking at a couple wire diagrams, I put that wire (control voltage for AC contactor) to the "Y" terminal. works now.
 
 

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