Screen flickering from overheating?

I would start off getting a good temp & fan monitoring app like this one: TG Pro for less than $20 US its well worth it!

Just knowing the one temp value doesn't offer much. There are quite a few thermal sensors within your system. In addition, you have one or two fans to keep things cool. Using a good monitoring app like TG Pro can make diagnosing heat issues much easier.

Depending on what you are running as an app at the time you could be hitting a few different possibilities.

• Dust build up internally on the logic board, fan & cooling fins
• Heat sink is defective
• Giving the age of the system you may need to refresh the thermal paste on the CPU & GPU's
• The battery maybe swelling causing pressure against the keyboard & trackpad causing a short.

I would also recommend you use this app to check your battery & charging logic: CoconutBattery.

Paste screenshots of the main screens of both TG Pro & CoconutBattery so we can see what happening here. Also what are you running on your system when the system is getting to this point?

Doesn't look good ;-{

Your battery is overheating presently at 38.7º C (101.66º F) with 70% charge and discharging at 35 watts! Looking at the system we see the PCH is at 68º C (154.4º F)! These values are way too high for an idling system.

In addition the Air Flow Proximity values of 42º C (107.6º F) & 52º C (125.6º F) is showing me your system is not able to keep up with the heat it's generating. The delta between the CPU & the heat sink should not be more than 12º C (10º F)

What are you running here? Clearly the system is overworked (overheating). You maybe asking this system to do more than it can. If you are doing heavy gaming here this system is just not up to long term play. You really need some heaver gear (desktop class system).

I suspect you'll need to first replace the battery here if you've been running the system like this for very long as you have likely cooked it!

In addition, I suspect you need to do some basic dust cleaning within the system as the system is clearly not shedding its heat overly well.

I would also clean off the old thermal paste on both the CPU & GPU's and apply a fresh coat of Arctic Silver Thermal Paste (which is what I use). Here's the IFIXIT guide you'll need to follow to take the logic board out: MacBook Pro 15" Retina Display Mid 2012 Logic Board Replacement and here is the IFIXIT guide that gets into how: How to Apply Thermal Paste