Central Air troubleshooting

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WebFire

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14,779 posts
May 21, 2014 9:35 AM
I'd rather take the advice of the OC than to hire a trained professional.

When I turn the AC on in the house, the house fan kicks on but the compressor/fan do not. I replaced the (dual) capacitor since the house sat a few years before we moved in over the winter. No change. The contactor pulls in and I can hear/feel it buzz, so I know the unit should be getting power, at least to that point. The wiring all looks good (no animal chewing). But I get nothing from the fan or compressor. The fan turns freely.

Any ideas?
May 21, 2014 9:35am
vdubb96's avatar

vdubb96

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2,210 posts
May 21, 2014 9:51 AM
Ask CC he specializes in A/C!
May 21, 2014 9:51am
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TedSheckler

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3,974 posts
May 21, 2014 10:27 AM
Sounds like low blower fluid.
May 21, 2014 10:27am
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WebFire

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May 21, 2014 10:32 AM
TedSheckler;1618337 wrote:Sounds like low blower fluid.
Can't be blower fluid. The blower is the part that works. Duh!
May 21, 2014 10:32am
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TedSheckler

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May 21, 2014 10:36 AM
If the fluid in the blower is low, there is an automatic shutoff in the compressor so it doesn't burn up.
May 21, 2014 10:36am
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WebFire

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May 21, 2014 10:53 AM
Where is the dipstick for that?
May 21, 2014 10:53am
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mcburg93

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May 21, 2014 10:55 AM
Its hard to say that the electric is fine unless you check the amp draw on each leg going to the unit. Is it the compressor motor buzzing or the fan motor buzzing on the unit? Do you smell any weird smells when you are around the unit? Do you see any oil spots around the unit? How old is the unit? Does it look like someone has messed with the service ports/valves?
May 21, 2014 10:55am
T

thavoice

Senior Member

14,376 posts
May 21, 2014 10:59 AM
WebFire;1618356 wrote:Where is the dipstick for that?
Someone already mentioned getting CC's advice.....
May 21, 2014 10:59am
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WebFire

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May 21, 2014 11:00 AM
mcburg93;1618359 wrote:Its hard to say that the electric is fine unless you check the amp draw on each leg going to the unit. Is it the compressor motor buzzing or the fan motor buzzing on the unit? Do you smell any weird smells when you are around the unit? Do you see any oil spots around the unit? How old is the unit? Does it look like someone has messed with the service ports/valves?
A buddy electrician is coming this weekend to check the electrical. At this point I think that may be what it is. There is no buzzing from the compressor or fan. The buzzing I was referring to is very faint and is just at the contactor. I visually inspected the wiring and it looks good, however, some of the connections seem a bit rusty. I may even try to clean those up tonight to see if anything happens.

Since neither the fan nor the compressor kick on, it makes me think they aren't getting juice. But my knowledge of AC is pretty limited, so I thought maybe someone had other suggestions, besides blower fluid.
May 21, 2014 11:00am
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Belly35

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9,716 posts
May 21, 2014 11:05 AM
Call a AC guy ... do it yourself AC repair never ends well....
May 21, 2014 11:05am
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WebFire

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May 21, 2014 11:08 AM
Belly35;1618365 wrote:Call a AC guy ... do it yourself AC repair never ends well....
I will if the electrical checks out. But some things are easy, like capacitors or contactors. Capacitor was $22, they'd probably charge me $200 to install it.
May 21, 2014 11:08am
Q

queencitybuckeye

Senior Member

7,117 posts
May 21, 2014 11:12 AM
Belly35;1618365 wrote:Call a AC guy ... do it yourself AC repair never ends well....
My theory is that it's already broken. If I can fix more things than I make worse, I'm money ahead.
May 21, 2014 11:12am
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mcburg93

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May 21, 2014 11:18 AM



You should have something similar to this behind the access panel on the unit. With the panel off turn the unit on watching to see if the contact relay pulls in. If it is buzzing You can change it or call a technician out to change it. Good luck
May 21, 2014 11:18am
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WebFire

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May 21, 2014 11:22 AM
mcburg93;1618373 wrote:


You should have something similar to this behind the access panel on the unit. With the panel off turn the unit on watching to see if the contact relay pulls in. If it is buzzing You can change it or call a technician out to change it. Good luck
Correct. In the OP I mentioned that the contactor pulls in. I can hear a slight buzz from it (sometimes I can only "feel" the buzz if I push on it with a screwdriver).

Are you suggesting I should change it in my case?
May 21, 2014 11:22am
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mcburg93

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May 21, 2014 11:23 AM
WebFire;1618367 wrote:I will if the electrical checks out. But some things are easy, like capacitors or contactors. Capacitor was $22, they'd probably charge me $200 to install it.


You are right. We charge 85 to show up and first half hour. Parts are usually marked up 150%.
May 21, 2014 11:23am
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mcburg93

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May 21, 2014 11:29 AM
WebFire;1618377 wrote:Correct. In the OP I mentioned that the contactor pulls in. I can hear a slight buzz from it (sometimes I can only "feel" the buzz if I push on it with a screwdriver).

Are you suggesting I should change it in my case?
Its really hard to diagnose without having some voltage readings. If its pulling in and there is a buzzing sound it could be the 24v coil on the contactor and it could be a capacitor. I would say its the contactor but with out the readings I really cant narrow it down completely
May 21, 2014 11:29am
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WebFire

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May 21, 2014 11:31 AM
mcburg93;1618382 wrote:Its really hard to diagnose without having some voltage readings. If its pulling in and there is a buzzing sound it could be the 24v coil on the contactor and it could be a capacitor. I would say its the contactor but with out the readings I really cant narrow it down completely
How much do contactors usually run? I already replaced the capacitor so we can eliminate that. Contactor seems like it should be easy enough to change.
May 21, 2014 11:31am
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mcburg93

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May 21, 2014 11:38 AM
WebFire;1618385 wrote:How much do contactors usually run? I already replaced the capacitor so we can eliminate that. Contactor seems like it should be easy enough to change.

I think they can run anywhere from 20 to 60 depending on amp and how many poles
May 21, 2014 11:38am
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WebFire

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May 21, 2014 1:10 PM
Ok I might just give that a try then. Thanks.
May 21, 2014 1:10pm
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WebFire

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May 22, 2014 8:38 AM
The contactor checked out good, and I get 240V input and output. So now I'm not sure.

Do these system "shutdown" when low on "freon"?
May 22, 2014 8:38am
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ernest_t_bass

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May 22, 2014 9:53 AM
May 22, 2014 9:53am
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WebFire

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May 22, 2014 10:13 AM
Let me try that.
May 22, 2014 10:13am
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WebFire

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May 22, 2014 10:13 AM
Nope didn't work.
May 22, 2014 10:13am
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mcburg93

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May 22, 2014 12:01 PM
WebFire;1618783 wrote:The contactor checked out good, and I get 240V input and output. So now I'm not sure.

Do these system "shutdown" when low on "freon"?

No it will still run just blow out warm air. You will also see your coils freezing up if its low obviously if it has none it will not freeze up. Did you check both capacitors the start and run capacitors?
May 22, 2014 12:01pm
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WebFire

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May 22, 2014 12:03 PM
mcburg93;1618881 wrote:No it will still run just blow out warm air. You will also see your coils freezing up if its low obviously if it has none it will not freeze up. Did you check both capacitors the start and run capacitors?
I replaced the dual capacitor. Didn't check voltage there though. Will try tonight.
May 22, 2014 12:03pm