Buzzing contactor and NO A/C


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Old 05-06-19, 07:11 PM
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Buzzing contactor and NO A/C

so I noticed that the blower and all was working but it wasnít cool. Went outside and the condenser was making a low buzzing/humming sound. The fan wouldnít kick nor the compressor. Tested for 24v and got 26.6v so I moved in to the 240 and was not getting anything on the 240. Moved to the disconnect and got 96v reading on it. Moved to the breaker and top pole read 120 and bottom read 26.4. My questions are as follows:

1. Why no reading at all at the contactor?
2. Why 96v at the disconnect?
3. I need to start by replacing the breaker, right?
 
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Old 05-06-19, 07:57 PM
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Welcome to the forums.

Actually the buzzing you are hearing is not the contactor. It's the compressor and fan humming from low voltage. Don't leave the A/C running on low voltage.

Yes..... that would indicate a defective circuit breaker or a bad connection to the bus bars.
You need to measure 240vAC across the two pole breaker.

Carefully remove the breaker and examine the lugs on the back of it. Check the lugs for burning. You can also visually inspect the bus bars inside the panel but DON'T touch them as they are live.
 
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Old 05-07-19, 04:30 AM
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It sounds like your checking voltage to ground.
Check across the circuit instead. Checking to ground can give you false readings.
 
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Old 05-11-19, 06:35 PM
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So I replaced the breaker and then discovered the fuses in the disconnect were blown. Replaced those and the fan came on but was spinning very slow. Shut it down and replaced the capacitor. I now have 240 coming all the way through the contactor but am still getting nothing from the compressor or fan. I even tried bypassing the defrost board to see if I could get the fan to engage and it wouldnít come on.
 
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Old 05-11-19, 06:43 PM
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Did you check for 240vAC at the equipment side of the contactor ?
That would be the side that is live when the contactor closes.
 
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Old 05-11-19, 07:10 PM
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I did.... 240 across the contactor
 
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Old 05-11-19, 07:53 PM
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Just to confirm.... not the side of the contactor where incomimg power connects.
The side that goes to the fan and compressor.

If there was 240v across the output of the contactor..... the compressor and fan should be at least humming.
It would be doubtful that the fan motor and compressor both went bad. I'd have to think a wire may have fallen off. Possibly off the contactor or the capacitor.
 
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Old 05-12-19, 03:28 PM
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Iím going to get back into it hopefully tonight and make sure. Could the defrost board be stopping power from getting to the fan and/or compressor?
 
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Old 05-12-19, 06:40 PM
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Novice... I am getting 120 at each leg to ground and the same on the other end of the contactor. Starting reading and digging and I think I may actually have a burned up disconnect. Iím getting 240 into the disconnect and 120 out each leg but Nothing combined.
 
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Old 05-12-19, 07:13 PM
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Then you have an open leg.
Don’t check to ground. Check across a the circuit.
 
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Old 05-13-19, 12:04 AM
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I did.... 240 across the contactor
I'm confused here. The contactor is after the disconnect.

You MUST get 240vAC at any place where it should be.
Into the disconnect........ out of the disconnect.
Into the contactor......... out of the contactor.
 
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Old 05-13-19, 07:52 AM
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As Roughneck stated I was checking them to ground instead of across the circuit. When I check across the circuit I get nothing. When I check each side to ground I get 120 on each.
 
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Old 05-13-19, 08:18 AM
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So you have a leg of power out.
You may have something grounded and that’s why the fan is spinning very slowly. If so use a lot of care. If your equipment isn’t properly grounded, the cabinet can become energized and kill you when you touch it.
There’s been documented cases of techs loosing their lives like this.
 
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Old 05-13-19, 08:31 AM
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I could see one of the contacts in the disconnect is burnt and looks like it may have some corrosion. Iím getting the 240 coming in to the disconnect but am not getting the 240 across the circuit going out of the disconnect only 120 per leg.
 
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Old 05-13-19, 08:35 AM
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In that case, the disconnect would need replacement.
 
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Old 05-13-19, 04:18 PM
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Disconnect has been replaced and I have the same issue. 120 through both legs but Iím not getting 240 across the circuit when I test the contactor.
 
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Old 05-13-19, 04:20 PM
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Do you have 240vAC where the wiring enters the disconnect ?
Do you have 240vAC where the wiring leaves the disconnect ?
 
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Old 05-13-19, 05:02 PM
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So I did not.... tested the brand new fuses I JUST put in and one is bad even though the indicator on it says it is good... 🤦🏻*♂️
 
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Old 05-13-19, 05:06 PM
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So was the fuse open when you bought it, or did it open when you restored power to the equipment?
 
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Old 05-13-19, 06:18 PM
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I honestly donít know since I didnít test them before putting them in. The indicator on the fuse doesnít show that it is blown. What would that mean if I put new ones on and one blows?
 
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Old 05-13-19, 06:29 PM
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It would mean you have a short on that leg, or something is wrong and causing a current draw higher then the fuse rating.
Have you checked the fuse with your meter to see if it’s actually open?
 
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Old 05-13-19, 06:31 PM
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I did check both with my multimeter. I also checked the compressor today and it tested good.
 
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Old 05-13-19, 06:42 PM
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So the fuse rung out ok? Or open?
 
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Old 05-13-19, 06:46 PM
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One was open the other rung out
 
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Old 05-13-19, 07:09 PM
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So now you’ll have to determine if the fuse was open when you bought it or something caused it to blow.
 
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Old 05-13-19, 07:21 PM
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Took them back to HD and swapped them. Put the new ones in and waited for the delay and the condenser started up! Went upstairs waiting for the cooling to start and heard a pop. Checked the air handler and the capacitor to the blower fan popped. It was already swollen so not sure if the other issues are to blame??
 
  #27  
Old 05-13-19, 07:23 PM
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Air handler and condenser are on (should be) two separate circuits.
 
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Old 05-13-19, 07:50 PM
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Actually had the correct capacitor that I saved from the Frankenstein capacitor someone built for the condenser. Put that one on the blower and it is now blowing 3 times better than before. Problem now is no cooling... I can feel heat coming from the evaporator in the handler....
 
 

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