Well yesterday i open my iMac... On power supply in the middle there is a small capacitor 47u 50V. Around that cap. PS produces too much heat. I change it with 47u 63V higher heat resistance, and guess what, no more sqicking sound!!!! 4SNS/1/4000000/1: VDOR it's logic board error related to Ambient light sensor. 28 Euro is the cost of new one in my country little bit expensive, but I replace it and VDOR error is gone. Another thing, The OPTIARC DVD RW AD-5630A its not compatible With this iMac, because some clips in the mounting bracket are not in the same position, I just remove them with the knife and mount it... Working better and cooler than old Uj- 85j TNX all 4 good tips IFixit ROCKS
You have to remove the battery. Under the battery you will find the trackpad sistem. On trackpad in the midlle there is a small torx screw. Just try to adjust that screw rotating with the screwdriver milimeter left or right and after that, test the filing of trackpad button, also putt the battery on and try click again. Repeat until you satisfed. Simple job, but big progress Nik