Outside AC unit NOT making ANY noise?


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Old 07-14-16, 08:33 AM
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Outside AC unit NOT making ANY noise?

Hello again guys! I had a wiring issue with my thermostat that was causing my AC unit to not work properly. Problem was fixed thanks to the help I received in a previous thread. Everything had been working fine for a month and a half...

So after arriving home from a 4 day vacation I come to find that the outside AC unit is not kicking on again. Unit had been working fine after the previous wiring issue. Thermostat calls for cool/clicks inside blower comes on and runs runs runs. No cool air/temp change. I am not hearing any sound coming from the outside unit. No hum/buzz nothing!

FURNACE: Amana air command sse
Outside AC unit: Amana High efficiency 12

-Have checked breaker.
-Replaced contactor and fuses.
-Replaced filter (inside unit)
-Cleaned coils.
-Thermostat is wired properly.
-Have tried turning power off to the system for ~1hr.

Still no change. No sound at all coming from outside unit NOTHING. Is this a possible capacitor issue or is it possible the thermostat wires have become faulty? I can not find any reset switches on inside or outside unit.

Really at a loss hear. Any ideas? Thanks so much for all the previous and hopefully future help!
 
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Old 07-14-16, 10:55 AM
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Have you tried taking a piece of wood or plastic and pushing on the center of contactor "spring" to close the contactor contacts? If so, do the compressor and condenser fan run? If they do, don't manually engage the contactor for any length of time (<30 seconds) until you determine why the contactor isn't engaging, as there may be high or low pressure switches which have tripped to prevent damage to the compressor. Report back what happens when you manually close the contactor.
 
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Old 07-14-16, 11:13 AM
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I just manually pushed in contactor and unit does come on.
 
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Old 07-14-16, 11:21 AM
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To proceed further, you'll need a multimeter (a cheap $10 one is fine). With the thermostat calling for cooling, measure the voltage across the two wires in the cable coming from the house. The cable from the house connects to the outside unit inside the unit using wire nuts. You should measure ~24VAC at the wire nuts. If you have 24VAC there, then move to the side terminals on the contactor (you can turn off the power to the outside unit while doing this since the 24VAC comes from inside the house). If you don't have 24VAC across the side terminals, you need to find out what is open. Often there will be a low pressure and/or high pressure switch in series with the 24VAC signal inside the unit. Either follow the wiring from the wire nuts to the contactor, or see if there is a wiring diagram inside the cover that you removed to access the "guts".
 
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Old 07-14-16, 11:54 AM
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If I understand correctly I am measuring where the thermostat wires connect via wire nut to the wire going to the outside unit? If so this is measuring 25.5? Measured voltage at the side of the contactor and I get nothing. Is this correct?
 
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Old 07-14-16, 12:11 PM
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You are correct. The readings you got are what I expected. It would appear that something is "open" between where the 24VAC (25.5 in your case) comes into the outside unit and the contactor coil. It's likely one of 3 possibilities:

Low pressure switch open due to being low on refrigerant

High pressure switch open due to excessively high system pressure. There should be a reset button (often red) on the high pressure switch. Push the button to reset the switch and check voltage at contactor again

Your unit has a Time Delay Circuit (TDC) that has gone bad and is open. If you have a digital thermometer, you can safely bypass (jumper) the TDC.

Your system may not have all 3 devices (Low/High pressure switches & TDC), but it probably has at least one (since you're not getting the 24VAC at the contactor). Either follow the wiring from the wire nuts to the contactor, or look at the wiring diagram if one is present. In fact, if there is a wiring diagram for the unit and you can post a picture of it, that would be great.
 
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Old 07-14-16, 02:55 PM
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Thanks again!



 
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Old 07-14-16, 05:28 PM
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The wiring diagram shows all 3 devices (low & high pressure switches and TDC). My guess is that the TDC is bad. It's the black "box" in the upper right corner of your picture with the yellow, blue, and black wires. To bypass it, remove the blue and yellow wires and connect them together. If the A/C now turns on (don't forget to turn the power back on to the outside unit before trying it), you've found the problem. I assume that you have a digital thermostat (as opposed to the old style mercury bulb thermostats), because you shouldn't bypass the TDC unless you do have a digital thermostat.

If bypassing the TDC doesn't solve the problem, check the pressure switches. They will be in the refrigerant lines. If one of them has a reset button, try pressing it.
 
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Old 07-14-16, 07:19 PM
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Good info from Bob.

I'm betting you find the reset button out on the hi pressure switch which would signify a possible condensor fan issue.
 
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Old 07-15-16, 09:02 AM
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Thanks guys. I am just getting to start on this right now again.

Should the high pressure switch be inside the unit? I see no reset on the lines on the outside of the unit. I am assuming it will be close to the condenser? I haven't opened up the top of the unit to get inside but with just a visual I am not seeing a reset. Will report back..
 
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Old 07-15-16, 09:32 AM
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Yes it should be inside the unit.
 
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Old 07-15-16, 11:11 AM
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Viola! I jumped the blue and yellow wires from the TDC and we are running smooth again. Outside unit came on quicker than I remember it every coming on. Is it safe to run like this until I get a new TDC? Do I need a new TDC or can I leave it jumped? You guys are great! TY TY
 
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Old 07-15-16, 11:51 AM
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You can run for a while without it, but I would replace it. It prevents damage to your compressor from short cycling that can happen with momentary power interruptions or other reasons.

Glad you are up and running.
 
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Old 07-15-16, 02:29 PM
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As CarbideTipped mentioned, the TDC will protect against a momentary power outage, whereas the digital thermostat will only prevent the system from turning on again too quickly via the thermostat. If you have occasional momentary power outages, then you should definitely replace the TDC. However, if momentary power outages are relatively rare (in your area), then you can probably leave it bypassed. When the TDC in my A/C unit went bad several years after the system was installed, I was told (by an A/C tech) that it was a part that failed frequently. His advice was to just bypass it. That was over 20 years ago and the system is still running. However, I rarely experience any momentary power outages, and the outage would have to occur while the compressor was running. It's a gamble, you need to decide for yourself.
 
 

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