# A/C Unit turns on for 15 seconds then turns off. Repeatedly!



## Rusbla

Hello,
I have a Carrier comfort series a/c unit, model 24ACA324. It's 3 years old and has been working well until a day ago.
When the thermostat sends the signal to turn the a/c unit on it does so as it should but it runs for 15 seconds and then turns off. It does this until I manually turn the unit off. The unit has been cleaned but still the same problem.

Any help or insight into this problem would be greatly appreciated. Thanks.


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## beenthere

Sounds like a pressure switch is shutting it off. I didn't think that model had them from factor y though.

look in it, and see if it has small devices with 2 wires on them in the lines in the condenser.


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## Rusbla

First of all Thanks alot for the quick response beenthere.

Yeah, I just checked and there are two devices in the unit. One has 2 yellow wires with orange stripes and the other has 2 blue wires with white stripes. If possible could you tell me which one it is. And are they difficult to change?


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## beenthere

When the A/C comes on, does the fan spin? if it does, then its probably teh low pressure switch. And that is the one on the large line.

But. that doesn't mean the switch is bad. means your system is probably low on charge. or your air filter is real dirty.

need gauges and EPA cert to check the charge.


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## HVAC_NW

You can connect a volt meter across the switch with the system running. You should read 24 or 0, depending on if its normally closed/normally open, but it should not change at all. If it does, its tripping. 

Then, its time for service call, to have a tech who really knows how to interpret pressures and see if its a bad switch tripping falsely or a legit trip. If it's a legit trip, the relationship between high and low side often tells metering device obstruction. Unusually high head can mean non condensible matter in the loop. This only happens if you had a bad leak in the past that caused air to be drawn into the system, or a tech screwed up. You'll need to have it evacuated, recharged with virgin refrigerant.


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## Rusbla

Yeah the fan spins when its running. I actually cleaned the condenser coil a day ago and replaced the air filter a week ago. 

The unit is only 3 years old so is it common to be low on charge?


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## hvaclover

Does virgin R22 bust it's cherry if a tech screws up the job:huh::jester::whistling2:


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## Rusbla

Thanks HVAC NW, I appreciate the response and insight. If only I knew more about electricity.


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## beenthere

Rusbla said:


> Yeah the fan spins when its running. I actually cleaned the condenser coil a day ago and replaced the air filter a week ago.
> 
> The unit is only 3 years old so is it common to be low on charge?


Well. 3 years ago. Lots of manufacturers were having evap coil problems. As in they leaked.

So yes, its common to have a leak in a 3 year old unit, today.

Not saying that is the problem, but it could be.


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## HVAC_NW

Rusbla said:


> Yeah the fan spins when its running. I actually cleaned the condenser coil a day ago and replaced the air filter a week ago.
> 
> The unit is only 3 years old so is it common to be low on charge?


Most residential units are hermetic system, so there are only two ways refrigerant can leak:

1.) tech error (highly likely..) 
2.) defective parts 

Do what you can using soap spray to look for leak at inside and outside coils. If the leak is at the coils themselves, get them replaced under warranty. 

Check all access ports and valves as well. 

Leak from anything other than factory assembled parts is defective install and chances are it was leaking from day one, but you didn't discover the symptoms until refrigerant got low enough to affect functionality. Grill the installing dealer. Tell them you expect the leak fixed. Don't let them get away with topping off. If you have to pay service call, don't pay for the same company that screwed up in the first place. Call someone else.

If you find a leak at braze made by an installer, then its definitely a defective install.


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