Specifications

is separated from the bottom housing could cause these parts to overheat. Short term
separation, where the thermal pads are not handled excessively
(an exception would be
if you are simply testing the logic board and only detach it for a few minutes)
,
does not require replacement. Refer to “Thermal Pad Installation” in this chapter for
detailed information.
Important: Diagnostic service cables allow the unit to run while the bottom housing is
open (as shown above). However, the computer cannot run for more than five minutes with
the bottom housing open. If it is open longer, the CPU may overheat and become
damaged.
Logic Board
iMac (Flat Panel) Take Apart - 27