Hello everyone:
I tried the SMC resetting and it worked for me when my screen was flickering with much lines. I believe that started when my fan started running and I left it trapped in my glove compartment in my extremely hot car. What a very careless thing to do. Thank Heavenly Father:
Instructions:
1. Shut down the Mac.
2. Plug in the MagSafe or USB-C power adapter to a power source and to your Mac.
3. Using the built-in keyboard, press Shift-Control-Option on the left side of the keyboard, then press the power button at the same time.
4. Release all keys, then press the power button again to turn on your Mac.