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I noticed today that the button on the thermostat isn't turning the fan on by itself. I tried today just to turn on the fan couldn't get it turn on.

Tonight we turn on the AC couldn't get cold air. Fan is blowing through the vents so I go outside to check the AC and the AC fan outside is not turning on compressor is working. Could it be the thermostat capacitor or the fan motor? I turned the fan it turns I didn't reset it I took the breaker out from outside I think I should hit the reset button. I don't know how long thermostat hasn't been letting u turning on the fan by itself A.C.

The AC was working fine last night until today when I tried to turn on the fan something happen and it still won't let me just turn on the fan without the AC

  • This is confusing because you keep saying "fan" but don't explain which fan. The "air handler blower" is what makes air come out of your vents. Call that a "blower". The outside condenser has two main components: a sealed compressor motor that makes a humming sound and a large cooling fan that blows air through the unit. Call that a condenser fan. Now, are you saying that the condenser fan does not come on and the compressor does come on (they should always come on at the same time)? – JPhi1618 Apr 9 at 2:53
  • Im saying the blower is working. but say the AC is off and I hit the fan button on the thermostat will not come on at all turn the AC on air comes out through the vents blower is working the outside condenser fan is not working. air is blowing through the vents, the condenser fan is not turning on is a thermostat fan button and the condenser fan both not working. I'm telling you all this so maybe maybe you can be where I'm at thank u for your help – ERIC Mulac Apr 9 at 10:42
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    Ok, that's what it sounded like you meant. I agree with the answer below from Machavity. – JPhi1618 Apr 9 at 14:07
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The most common reason for something like this is the capacitor on the compressor (the outside part) has gone out. You can do this yourself, you just need to be extra careful if you decide to do so.

Cut off the power to the compressor

You should have a power disconnect switch feeding your compressor. Turn it off. Use a tester to confirm it's off. You'd be amazed how often disconnects have been bypassed after the fact.

Remove the cover to the side where the capacitor is

You should have one corner that is separated from the open area in the middle. Remove the cover and you should see the capacitor inside (almost always a round cylinder with wires attached). Be aware that the capacitor is still charged even with the power off.

Discharge the capacitor

You probably have a C/Common, a F/fan and a Herm(compressor) terminal. Discharge is recommended. I would suggest using a 100 ohm resistor (not recommended to use a screwdriver here). Touch the common to the herm for a few seconds, then do the same for the fan side.

Remove the capacitor

Take a picture of the wires and then remove the capacitor. The connectors push on to tabs. There's typically a strap to hold the capacitor.

Install the new capacitor

If you can't wait for an online delivery, contact a local HVAC company to see if they'll sell you a capacitor directly. Put the wires back on, scrap it back in and turn the power on.

Your compressor should now work. If not, you might need to consult an HVAC company on what else could be wrong.

  • This is very location dependent, but some HVAC supply stores will not sell to the "public" and some cities have stores that cater to homeowners simply because the other type of store exists. – JPhi1618 Apr 9 at 3:04
  • @JPhi1618 True, but I've found most HVAC companies would rather sell to you at some minor profit on the Capacitor than to have you order it online and bypass them totally. The vast majority of people do not want to fiddle with capacitors, especially when it goes out in the middle of Summer, and HVAC companies can make a killing on after-hour service calls. – Machavity Apr 11 at 12:40
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I have a Lennox heat pump system and had a similar issue this winter with the outdoor unit not coming on. It ended up being a bad valve inside the outdoor unit. I am not 100% sure but I believe it was the expansion valve. The “local” Lennox tech was able to fix it for about $250 but he had to travel 40 miles.

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