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Phil , Mechanical Engineer
Category: HVAC
Satisfied Customers: 7489
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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every time it hits 90 degrees out side my ac will shut off..

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every time it hits 90 degrees out side my ac will shut off.. i had my motor replaced last year what else can i do or what is wrong with it

Welcome welcome to Just Answer!.

Tell me please how old the unit is approximately, and if you live in the city or the country and if you have pets or not.

Pet hair and dirt can clog the condenser and cause that problem. The condenser may look clean but actually be clogged with dirt **between** the fins

Tell me when the problem first started.

There can be other causes as well, such as a poorly trained technician putting too much refrigerant in the system. We need to do a few tests to see if thats the case or not

First test:

Put a thermometer in the cold air outlet closest to the furnace or air handler.... tell me what the temperature is after 4 minutes..... then use the same thermometer and put it in the room near the return air grill and tell me what the temperature is.

Tell me if you turn the AC on in the morning and leave it on all day, or do you wait until the house is hot, then turn on the AC

Tell me if the AC goes off by tripping the breaker or not. What do you have to do in order to get it running again.

Please try to answer each of these questions in detail, I need all that data in order to do a proper diagnosis.

We can go from there until we get this figured out with no time limit.


Customer: replied 3 years ago.

four dogs in house, live in suburbs, been like this since i lived here bout 4 years, doesnt trip breaker and comes back on by its self when temp drops outside


Hello again, thanks for the information.

I have been in the business for 52 years and so far have not seen a system with a thermostat outside that shuts down the outside unit when it gets hot (above 90F in this case). its an overheat issue I think.

What i think is going on is that the compressor itself over heats when it starts getting close to 90F and then goes off on its *internal overload... it takes 2 or 3 hours for the compressor to cool enough to come back on, that happens all by itself.

That should not begin to happen until it gets above 100F outside.

When it happens at 90F it is usually caused by a dirty condenser coil on the air conditioner outside.... if the dogs spend a lot of time outside, there will be dog hair and dirt on the condenser coil fins, and deep **between*** the fins.

Do this:
Turn the power off to the outside unit at the breaker panel or the disconnect switch on the wall next to the outside unit.

Then remove the service panels that enclose the condenser fan so that you can see the back side of the finned condenser coil. .. if the fan is on top of the unit you do not have to remove any panels as a rule.

Using a high pressure garden hose **blast** water through each square inch of the coil until you can see water coming out the other side.... that takes about half an hour... don't get the fan motor or other electrical parts wet... can wrap the fan motor in plastic sheeting to keep it dry.

After using the garden hose, let the unit sit for half an hour... put the panels back on and turn the power back on.

Let me know how that goes... thats step one, w\

We can go from there as necessary as long as you rate my answers so far *positively, there are no time limits.

Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7489
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
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