Compressor has trouble starting

colt357_2004April 26, 2009

Here in Texas we run the air conditioner on at least some days even in January. So far this spring has been mild but we hit the 90s the other day. I noticed a few weeks before that when the AC started, there was a buzzing sound, several times and then you could hear the compressor start.

We are renting and I called the land lord and he didn't do anything for a couple of weeks. Now it seems when the AC starts, it makes that noise about every five seconds until the compressor starts and it begins cooling. Sometimes for several minutes. It works great after it starts but every cycle it hard starts again.

My land lord is in the building trade and he sent this guy over that speaks broken English and we go out to the unit and he opens it up. It's still pretty clean for two years old. No fire ants in the contactor or anything like that.

Anyway he observes what I described. He tested the capacitor with a volt/ohm meter. It checked out OK.

So he says it needs a "tune up". Clean the coils inside and the outside unit. He checked and charged the coolant. It didn't need much. He did have the gauges, but I didn't see a recovery device.

I'm no HVAC guy, but I have worked in the swimming pool industry for 27 years and I know a little about allot of things. I think there is something wrong with the compressor. Or this 1960 house doesn't have enough electric service for it. However it worked two summers without doing this, so maybe not.

When he replaced it two years ago, the guy he sent then said the breaker was too small. He replaced it and it didn't fix the old unit, that may have been original. So he took it out and put the old one back in. I think my LL is a cheapskate.

He finally broke down then and got this unit. A Rheem Classic 10seer. The cheapest one they make. It's still more efficient than the old one.

Sorry this got so long, but you can't diagnose without the facts. And like we do in the pool business, we tell people we can't diagnose over the phone.

So to recap.

Two year old Rheem Classic 10 seer.

Thermostat calls for it to come on.

Fan starts, inside and out.

Electric buzzing sound comes from somewhere. Standing over the unit it actually seemed to come through the conduit.

Buzz is intermittent, until compressor kicks in.

Tech says cleaning it will solve the problem.

I'm not buying it. Something else is wrong.

LL is cheap and unit may have gone out of warranty.

All I want is some opinions, I can tell the LL so he fixes it before it's 99 every day and it fails. The LL messed around two years ago to the point we had to stay in a hotel for two nights. He paid for the hotel and bought a new unit.

You would think he would learn.

Your thoughts?

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"Buzz is intermittent, until compressor kicks in."

Could be a loose electrical connection, or even an about to fail contactor, or a starting capacitor about to fail.

Compressors pull a very large current at start up.
Look on the unit nameplate and there should be an LRA (Locked Rotor Amperage) specified.
This is what the unit can pull trying to get started up.
It only should last a few seconds though.

Slow starting can be caused by voltage drop.
A bad connection or bad contactor can cause extra drop.

If the unit is only around two years old but sees heavy use, I would inspect the contacts in the contactor carefully.

Cheaper units often have copper contacts that pit and wear badly.

    Bookmark   April 26, 2009 at 11:39AM
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Check for a volage drop at the breaker and fuses disconnect. If your wiring is undersized it may be causing this problem. If no large voltage drop, replace contactor as cheap ones have a weak coil taht sometimes buzz. The unit you have is a piece of &&^%$##@@!

    Bookmark   April 26, 2009 at 12:00PM
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So I gather this story about it needing a good cleaning is most likely NOT the problem. Tech1 I appreciate your candor. It's not one I would have bought if I owned the home. I notice he put a Goodman, on the house next door. He owns that house too. He owns about four houses on the block and they all were built from 55 to 60 according to tax records.
He was a friend of mine before we rented from him, and I want to stay friends. I have access to a volt meter and severl pretty handy friends, but no HVAC pros. I want him to fix it. Not mickey mouse around until it won't start at all. My wife has asthma. I could camp out for a day or two. She can't.
Thanks for the replies so far. I can take those ideas to the LL.

    Bookmark   April 26, 2009 at 12:45PM
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You have had real good info, there is one thing i would add. When checking
the power, check at the furnace also for line volt. Your out side contractor
probably has a 24 volt coil and if the 24 volt power if down too low it will not snap the contractor in good enough, They will chatter and buzz. The transformer
in the furnace will start out about 27 volts if the line voltage it up to 118 , but the 27 volts will drop fast if the line volt are down . You also lose the 24 volts in long wire runs and through points, and also if they used 20 gage wire.
Later Paulbm

    Bookmark   April 26, 2009 at 4:46PM
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