Air conditioner humming/buzzing

Old 05-27-20, 07:53 PM
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Air conditioner humming/buzzing

I'm a rookie when it comes to hvac understanding so please bare with me!!!

This last winter my heat pump/ furnace was working and would each run depending on how cold it was... One day this early spring I heard the air conditioner humming/ buzzing. I didn't think anything of it and thought it was in a defrost cycle. a few hours later I heard it again and stayed on for 10 min straight so thought something was stuck.... I went inside and switched thermostat to emergency heat to shut heat pump off... since then I forgot all about this...

i just turned my thermostat to cool for the first time this year..... i hear the same noise at the air conditioning unit..a buzzing/ humming. ... i quickly researched and found most issues pointed towards the capacitor... i opened my cover and immediately noticed my contractor appears stuck down... so I switched my attention to stays down regardless of my thermostat setting is heat, cool, off, etc... i went to my furnace and shut power off..i left power off...i rechecked my air conditioner and contactor still stuck down.... i researched again, and site said to check the r to y wires on air conditioner and read 0v so contactor should not be down.... i went and turned fuse back on to furnace and rechecked voltage at air conditioner. I now have 29v between r and y... contractor still stuck down....

What wire combination do I need to check when thermostat is calling for cooling? Or what else should I check voltage on?

My thoughts are to get a new contractor as I don't think it should be stuck down.... but if the contractor is really stuck down shouldn't my issue be that the ac unit should be always running, correct???

Am I possibly looking at capacitor issue as well or could this all be tied back to contactor issue????

Or have I totally messed up my troubleshooting??

Thanks in advance!!!
Old 05-27-20, 10:25 PM
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so please bare with me!!!
You mean I have to get naked.

You have a heat pump and a gas furnace ?
Or a heat pump with an electric furnace/air handler ?

While you are messing around..... turn power off to the condenser. (pull disconnect)
The wires you are interested in are Y and C. C is basically ground. Y becomes 24v during a call for cooling. So there should be 0v between Y and C when not calling for A/C.

You said the contactor was still engaged when the furnace was turned off. That would pretty much point to a contactor problem as all 24v power comes from the furnace.

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