Fans run continuously

Room temperature is normal? I know it is warm here.

Click on this link to read about fans and fan noise in your Apple product --> About fans and fan noise in your Apple product - Apple Support

Make sure it isn't a runaway system component. View energy consumption in Activity Monitor on Mac (was: Apps can affect Mac performance, battery runtime, temperature, and fan activity) - View energy consumption in Activity Monitor on Mac - Apple Support - Activity Monitor "When an app isn't responding or working correctly, it might use more of the processor (CPU) than it should, even when the app doesn't seem to be doing anything. As the CPU gets busier, it uses more energy, which reduces the length of time that your Mac can run on battery power. It also generates heat, which can cause the fans in your Mac to spin faster. "

Massomo wrote:

I tried to run diagnostic through internet recovery but the process was stuck and I received the message

"Error: 0x800 000 000 000 000, Cannot Load 'EFI/Drivers/TestSupport.efi'

Status: 0x00000003

Unfortunately this is somewhat normal. Apple broke the ability for some older Macs (usually the 2012 model) to access the online Apple Diagnostics with a later system firmware update. Apple just never update the "TestSupport.efi" bootloader located on the Apple server to work with some of the later system firmware. It is strange because only some laptops are affected (I never had time to do a proper investigation to determine which system firmware is affected). Unfortunately this can also prevent the older local diagnostics to work as well.

You can check the following site to see whether they have an archived copy of the local diagnostics available for your model laptop (IIRC the diagnostics links in this article are all to the official Apple servers):

https://github.com/upekkha/AppleHardwareTest

I have come to the conclusion that my "System Management Controller chip" is faulty and needs to be replaced. I saw a lot of indications of behavioral change of the laptop that are similar to the description shown in this web page: https://www.cursosapple.com.br/certificacao-apple-exame-9l0-010/the-function-of-the-smc-in-an-intel-mac/

Definitely a possibility, but most of the time unless there has been accidental liquid damage, I find another component has failed where one of the sensors is no longer responding.

Massomo wrote:

Thanks for the response. The parts were replaced by an expert may be something went wrong during the process. The guy suspects that the sensors may be faulty.

Good guess. If any of the laptop's temperature sensors are not seen or working properly, then the laptop will run the fans at high speed as a safety precaution to prevent the Mac from overheating. Try running the Apple Diagnostics to see whether it detects any hardware issues, although keep in mind that the diagnostic may fail the third party battery even if the battery is in good condition so that is not necessarily a problem unless it also does not detect the Battery's temperature sensor.

You can try adjusting the fan speed using the Macs Fan Control app. This application allows you to manually control the fan speed on your MacBook Pro 13" Retina Late 2012 running MacOS Catalina version 10.15.7. It might help you manage the issue of the fans running fast after powering on.

Who replaced the components? Maybe that person can help.

I'm not familiar with that model but it sounds like a sensor or some other component got a little "over-fixed" when the work was done.