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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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We are having issues with our A/C unit. We have a nest

Customer Question

we are having issues with our A/C unit. We have a nest thermometer and it is reading 78 and we have the air down to 60's and it is not cooling
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: Yes, had an HVAC technician out yesterday and he refilled the coolant (which was low), but he checked the filters and they are all fine. Also, there is no leak.
JA: Do you plan on doing the work yourself?
Customer: Yes, for now since there are no HVAC companies that can come out right away
JA: Anything else we should know to help you best?
Customer: We suspect there is a setting in the Nest thermostat that needs to be changed/reset, but not sure what it is. The last time the technician came out, he said that was the main problem and made some changes, but we don't know what he did
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the HVAC Technician about your situation and then connect you two.
Submitted: 4 months ago.
Category: HVAC
Customer: replied 4 months ago.
We need an HVAC expert that is familiar with the Nest thermostat system. Thank you!
Expert:  Phil replied 4 months ago.

Hello, if the system cooled before, but not now, the problem is most likely not related to the Nest thermostat.. tell me if any air is blowing out of the vents or not, and if the largest copper tube connected to the outside unit is cold or frosty, and if the unit outside is running or not.

the problem Nest encounters is that about 10% of the time it encounters a furnace/ air handler or heat pump that it was not designed nor intended to handle...

I need the brand name and model number of the furnace or air handler, and a photo of the wiring diagram glued to the inside of the blower service panel to assess the situation for you... photo must be taken up close, well lit and exceedingly well focused. You can use the paper clip icon at the right end of your tool bar to attach the photo.

I also need to know which model of Nest you have (there are 3)

Customer: replied 4 months ago.
Hi Phil,Yes, there is air blowing out of the vents and it feels like room temperature air (not cold).The largest copper tube connected to the outside unit is not cold. It is running and we can see the fan running. The brand name of the unit is very hard to make out (it is pretty old). See all photos attached.The Nest model we have is this one: We got it about three years ago. Please let me know if you have any other questions.
Customer: replied 4 months ago.
Here is another photo of hvac unit.
Expert:  Phil replied 4 months ago.

Hello again, that unit is at least 15 years beyond is normal 15 year life span, and all this time with the *same fan motor... I have to call it a miracle unit at 30+ years old.

The fact that the fan is running tells us that the thermostat is working properly, and that the problem is inside the unit. It is probably not a good idea spend any money at all on repairs and should be replaced... even if you are going to sell the property that old unit will be a big deduction from the sell price.

If you wish to attempt a repair you might get lucky and the contactor that puts power to the compressor could be bad, or if you are not lucky one of the wires attached to the compressor could be burnt off.

Inspect all that, with the power off, we can go from there

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