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Old 09-08-2013, 06:28 PM   #1
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AC stopped blowing cold air


Hi all,

This past Friday, my ac was on but stopped blowing out cold air. I checked the unit outside and the fan was not moving. I tried giving it a jump by moving it with a stick, but no luck.

I researched and I come to the conclusion that it could very well be the capacitor. I opened up the unit to take a look. If I were to go about replacing the capacitor, would it be the black on with 2 terminals? But then I saw another capacitor hanging underneath with 3 capacitors? So does this mean the unit has dual capacitors, and if so, which do I replace?

Also, where can I buy capacitors? I keep hearing these places but they only seem to sell to contractors and such.

thanks so much. It's no fun not having cold air in 90 degree weather.
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Last edited by miamimike88; 09-08-2013 at 07:03 PM.
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Old 09-08-2013, 09:42 PM   #2
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AC stopped blowing cold air


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Originally Posted by miamimike88
Hi all,

This past Friday, my ac was on but stopped blowing out cold air. I checked the unit outside and the fan was not moving. I tried giving it a jump by moving it with a stick, but no luck.

I researched and I come to the conclusion that it could very well be the capacitor. I opened up the unit to take a look. If I were to go about replacing the capacitor, would it be the black on with 2 terminals? But then I saw another capacitor hanging underneath with 3 capacitors? So does this mean the unit has dual capacitors, and if so, which do I replace?

Also, where can I buy capacitors? I keep hearing these places but they only seem to sell to contractors and such.

thanks so much. It's no fun not having cold air in 90 degree weather.
The vertical one is a dual cap. The black plastic one is a start vapid start with the dual cap first but recommend replacing both. There is also a start relay in there but that only affects the compressor starting. Before u replace make sure u check the ratings on it. You don't need to be a contractor to buy from Graingers. Also most supply houses (around here) will sell to non-contractors but they just get charged a bit more

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Old 09-10-2013, 03:12 PM   #3
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AC stopped blowing cold air


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The vertical one is a dual cap. The black plastic one is a start vapid start with the dual cap first but recommend replacing both. There is also a start relay in there but that only affects the compressor starting. Before u replace make sure u check the ratings on it. You don't need to be a contractor to buy from Graingers. Also most supply houses (around here) will sell to non-contractors but they just get charged a bit more
Thanks for the info! So I went to Graingers to get a replacement for the black one. Question: the capacitor on the bottom is the new one I bought, does it matter that it doesn't have the that thing it the middle connecting the 2 terminals? Would it make a difference?

thanks!
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Old 09-10-2013, 03:48 PM   #4
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AC stopped blowing cold air


I believe you bought the wrong capacitor. You bought a start capacitor that assists in starting the compressor. Since you stated your fan was not coming on you should have replaced the run capacitor I labeled "fan" in the photo. It appears that at sometime someone used a dual run capacitor to only run the compressor and a separate run capacitor for the fan. It looks like a universal fan motor wiring and that is probably why. You should be good (if the fan is the only problem) if you replace the run capacitor with the two brown wires going to it. Make sure to replace it with a capacitor with the same specs.

Before you replace the capacitor though you probably need to check some other items:

You stated that when you checked the unit the fan was not moving. Was the compressor running? Was there power to the disconnect? Is the inside blower working?
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Old 09-10-2013, 04:30 PM   #5
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AC stopped blowing cold air


firedog is correct but to simplify it to a few words that a non Pro can understand. replace both of the other ones as they can affect the fan motor if either one is shorted open or very weak. Americanhvacparts.com is a good site.
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Old 09-11-2013, 02:20 AM   #6
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One more quick note. When replacing caps make sure they are secure won't move around at all and the metal terminals won't short out on any other metal surfaces. I came across one the other day where the last guy there replaced fan motor and cap but did not secure cap. So it shifted in cabinet from vibrations and blew a small hole in the dual capacitor which preceded to leak its oil all over the compartment on unit luckily it tripped breaker before any real damage started
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Old 09-11-2013, 10:05 AM   #7
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One more quick note. When replacing caps make sure they are secure won't move around at all and the metal terminals won't short out on any other metal surfaces. I came across one the other day where the last guy there replaced fan motor and cap but did not secure cap. So it shifted in cabinet from vibrations and blew a small hole in the dual capacitor which preceded to leak its oil all over the compartment on unit luckily it tripped breaker before any real damage started
Wow, thanks for the heads up! I'll be sure to secure it I put it in.
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Old 09-11-2013, 10:08 AM   #8
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AC stopped blowing cold air


yeah, use metal perforated strapping.
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Old 09-11-2013, 10:12 AM   #9
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I believe you bought the wrong capacitor. You bought a start capacitor that assists in starting the compressor. Since you stated your fan was not coming on you should have replaced the run capacitor I labeled "fan" in the photo. It appears that at sometime someone used a dual run capacitor to only run the compressor and a separate run capacitor for the fan. It looks like a universal fan motor wiring and that is probably why. You should be good (if the fan is the only problem) if you replace the run capacitor with the two brown wires going to it. Make sure to replace it with a capacitor with the same specs.

Before you replace the capacitor though you probably need to check some other items:

You stated that when you checked the unit the fan was not moving. Was the compressor running? Was there power to the disconnect? Is the inside blower working?
Thanks for the info. I got new parts for the Start cap and run cap ("fan") and the compressor part will be coming in tomorrow. I'm going to install the 2 parts tonight and see what happens.

If I remember correctly, I didn't really hear anything, or at least I don't think I did from the outside unit. There was warm air blowing inside the house and the air handler was making noise but the outside unit didn't have much sound to it.
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Old 09-11-2013, 10:16 AM   #10
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AC stopped blowing cold air


check for 220-240 volts across the incoming side of the contactor. not to ground.
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Old 09-12-2013, 07:32 PM   #11
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AC stopped blowing cold air


Hey guys,

I just replaced the start and run capacitor ("fan") with new ones and when I went to go turn on the AC, I could hear the air handler going on but for the outside unit, nothing at all. No noise, no fan movement, nothing. I tried kickstarting the fan with a stick but no luck. I had ordered a new part for the compressor as well but hasn't come in yet (I put the old one back in).

Could it be the contactor? I don't have a multimeter at the moment to check the voltage but I could get one easily. If that's the case and I should check the voltage, how would I go about doing it? There's a pic earlier in the thread of the contactor. Which wires do I check and do I check it when the AC is on?

thanks again!
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Old 09-12-2013, 07:32 PM   #12
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check for 220-240 volts across the incoming side of the contactor. not to ground.
Hi Yuri,

Which would be the incoming side of the contactor? And where exactly on the contactor do I check for it?

thanks.
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Old 09-12-2013, 07:53 PM   #13
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AC stopped blowing cold air


Here is an image of the test points you will need to check with a multimeter. Be extremely careful as the 24oV is live and can be lethal!
Set the multimeter to 600VAC when testing the 240V test points. The incoming voltage is between L1 and L2 in the diagram. Place one lead on L1 and L2. It should be atound 240V
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Old 09-12-2013, 08:36 PM   #14
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Here is an image of the test points you will need to check with a multimeter. Be extremely careful as the 24oV is live and can be lethal!
Set the multimeter to 600VAC when testing the 240V test points. The incoming voltage is between L1 and L2 in the diagram. Place one lead on L1 and L2. It should be atound 240V
Awesome diagram. Thanks.

As for the procedure of testing it (I wanna be careful cause I am aware of the danger of it):

1) Do I have the AC on or off?
2) How can I be sure when I place the leads that I won't get shocked? Are gloves recommended for using the multimeter?
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Old 09-12-2013, 09:22 PM   #15
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To test the 240V the power has to be on. That is what makes it dangerous. Carefully place one probe of the meter on the L1 and the other lead on the L2 to get your reading. Just make sure the ground is dry and remove all rings, watches, bracelets, necklaces and etc and remove any loose fitting clothing. Gloves are optional. I prefer to work without them. After you test to see if you have 240V coming in you can do the other tests listed on the diagram. Don't hesitate to ask if you have any doubts. The first time you work with high voltages it is intimidating. But as you have more and more practice and get proficient you gain more confidence always remembering the danger and the need for strict focus.

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