A/C Fan starts then stops, capacitor question

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Old 07-03-20, 08:55 PM
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A/C Fan starts then stops, capacitor question

Hello everyone new here, trying to diagnose my A/C problem, and decide if it's worth fixing.


Background: About a week ago my A/C died, the fan would not even start, I would just hear buzzing.

Did some research and I changed my capacitor, everything worked well for about 5 days, and today my A/C died again, this time through the fan would start and run for 10-30 sec, and then I would see/hear some sparking coming from the black terminal in the picture below and the fan would stop. It might be hard to see in the picture but there is a horizontal tab that was sparking and popping in and out near the blue wire.

My orignal capacitor was a 30+5, 380 vac
I took it to an HVAC supplier and they gave me a 30+5, 370/440 vac, telling me it was ok to install.

I mention this because I called up a random HVAC repairman and after describing my problem, and he said maybe your capacitor is the wrong one. But he didn't sound too sure...

Is the capacitor the problem? Did the supplier give me the wrong one?

If not what could the problem be, and approximate cost to repair? I was quoted around 2k to install a new A/C so if the problem would cost hundreds to repair I might just pass and get a new one (my ac is from 2008)

Thanks for any help



 
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  #2  
Old 07-03-20, 09:04 PM
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So the contactor was opening and closing?
Check coil voltage. But it sounds like a pressure switch may be cycling open and closed. Does your unit have pressure switches?
That carflex should be fixed before a wire chafes.
 
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Old 07-03-20, 09:27 PM
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The black unit is your contactor which controls the Start and Stop of your condenser unit. When the blue and brown wires provide 24V electricity, the black tab will push in (that start the system), when the 24V was cut off, then the black tab will pop out (that will stop the system), So use a meter and check the blue and brown wire and see if the 24V is still there and if the black tab's position is in or out ? You may have a lose connection at the blue and brown wire's terminal.
 
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Old 07-03-20, 10:11 PM
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The capacitor is not the problem.The two capacitances are correct.
A higher voltage than the original is good.

My bet would be on a low refrigerant charge.
 
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Old 07-03-20, 11:44 PM
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Thanks for the responses.

I don't know what/if my unit has pressure switches..

I have checked all the wire connections they are all firm.

I think I read that low refrigerant means there is probably a bigger problem such as a leak somewhere because the refrigerant is supposed to recycle itself.

How would you rate this on the scale expense wise? As I said I'm also considering a completely new unit if the repair is complicated/expensive.

 
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Old 07-03-20, 11:52 PM
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If you post another picture from a little further back we can see if you have a pressure switch.
( If the brown and blue wires running to the right in your pic connect directly to the wire nuts going inside of the house you do not have a pressure switch)

A picture from further back may also reveal if the capacitor is correctly wired.
I would expect 2 yellow wires on C, a blue wire on Herm and a brown wire on the Fan terminal of the cap but this varies by brand.
 
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Old 07-04-20, 08:45 AM
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So I turned off A/C off last night, and this morning I decided to boot it up again just to see.

Now when the thermostat calls for cool my unit just sits there dead. The contactor no longer engages (black tab pushes in) to start the fan at all, before it would keep trying to engage, fan would run for a bit then die

Might have been unsafe.. but tried engaging the contactor myself (gloves/tool) and the fan started. I didn't hold it for long, but I now suspect the contactor is defective?

This is probably something I can handle myself, just take some pictures and shut the power off,




pretty sure the wiring is correct, i was very careful about it

Does not look like I have pressure switches?
 
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Old 07-04-20, 09:37 AM
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Hi, did you test for 24VAC on the Blue and Brown wires when the Tstat is calling for cooling?
Geo
 
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Old 07-04-20, 09:56 AM
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It looks like the incoming 24v goes directly to the contactor but I see two light blue wires.
One looks to be going into the unit. Can you see where it goes ?

Not a great picture but that's a pressure switch.



 
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Old 07-06-20, 09:06 AM
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I was away for the weekend and came back today.

it looks like the contactor is engaging again and my a/c has been running for about an hr with no problems..

I didnt chg a thing. Super weird

I did measure if the blue/brown wire were providing 24v and they are.

 
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