Old Bryant Unit Short-Cycling


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Old 07-24-19, 06:39 PM
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Old Bryant Unit Short-Cycling

I have an older Bryant unit that is short cycling extremely bad. It will run for a while then go through fits of short cycling and is much worse the warmer it gets outside. I’ve attached pictures and a video of what it’s doing. I’ve replaced the contractor, both capacitors, the thermostat and the compressor fan motor. I just checked my electrical connections and they all seem to be tight. Could it be low on coolant or another problem that I can try to fix? Any help is appreciated. Thanks,
 

Last edited by PJmax; 07-24-19 at 07:26 PM. Reason: removed links
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Old 07-24-19, 07:29 PM
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Welcome to the forums.

Your picture links were to a private google account. If you want to use that account to post pics publicly..... you need to select "public" for those pictures. Otherwise post them directly to the board..... How-to-insert-pictures.

It sounds like you are low on refrigerant. You can use a voltmeter to confirm the 24vAC where the thermostat cable connects to the outside condenser. There will usually be wirenuts there. If that 24v is there and the unit is cycling..... you are low.
 
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Old 07-27-19, 12:38 AM
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Turns out

Turns out, I am not low on refrigerant. I had someone come out and look at it, and his best guess is that I have a shirt somewhere in my unit. We have both looked and cannot find it. Anyone had a short that led to rapid short circuiting. My contractor is almost constantly chattering from the short.
 
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Old 07-27-19, 10:45 AM
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Your contactor needs 24vAC to close. So if you have a short before the condenser.... that could be the problem. If you were low on refrigerant.... that switch opens the contactor line and can also cause it to chatter.

Typically if there is a short in the 24v line to the contactor..... the fuse will blow in the air handler or the transformer will burn up. You will need a meter to check for the 24vAC and see where it's getting lost.

99 out of 100 times the chatter is cause by the low pressure switch which is cycling based on low pressure.
 
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Old 07-27-19, 04:48 PM
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Bad LPS

Could it be a bad low pressure switch? I have 24v coming into the contactor.
 
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Old 07-27-19, 07:33 PM
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If you connect your meter directly to the contactor coil, and the voltage is stable near 24vAC, and the contactor is chattering...... the contactor is bad.
 
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Old 07-28-19, 06:32 AM
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Hi, so the contractor who looked at it, I assume he put gauges on the system to determine it was not low on refrigerant, if you had a short as mentioned you would have either a blown fuse or burned up transformer, if anything it would a loose connection somewhere, put a meter across the low voltage terminals on the contactor and see if there is a constant 24 VAC .
Geo
 
 

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