Faulty iMac LCD proximity sensor

[Vojoor]

Hey everyone, about two years ago I got my hands on a used iMac (21.5-inch, Late 2013) for free, I swapped the HDD and put in a SATA SSD.

The machine has been working just fine until I noticed today that the fans are going full blast and the system was really slow. I didn’t remember putting anything for it to work on it so I checked the activity monitor which says that about 60%-70% are used by kernel_task.

Quick google search and I found out that the system may slow itself down if there is a heat issue. After checking Macs Fan control I saw all temps at 30-40 degrees Celsius (86F-104F). All except one of the LCD Proximity sensors which is at 125C (257F) while the other one is normal. My guess then is that the faulty sensor is the culprit. I’ve seen that a replacement one can be had for cheap, but before opening it up and trying to replace it, I want to make sure that that’s the reason for it. Now my question, is there any way to disable/manipulate the sensor‘s information? So the system thinks all is nominal?

I’ve already done SMC and PRAM resets, didn’t fix the issue unfortunately.

 

[OddOod]

Given how locked down MacOS is I'd bet that there is no software solution for this. I'd guess that you knocked around the sensor while doing the swap.

[Vojoor]

3 hours ago, OddOod said:

Given how locked down MacOS is I'd bet that there is no software solution for this. I'd guess that you knocked around the sensor while doing the swap.

 

The swap was 2 years ago and it was all just fine, so it may have come loose just recently. 

[Vojoor]

Okay, this may sound like a bad joke but after having tried everything Software side possible I went on to literally hit the screen with my palm and after just a second or two I saw the temp drop to a normal value, fans stopping and kernel_task drop to 1%… I can’t believe it 

[tkitch]

Percussive Maintenance.  Works 100% of the time, about 28% of the time!