Question : Problem: Dell Optiplex fan and thermal issues

I have a Dell Optiplex GX280 that is having startup issues. It appears to be a thermal issue as the fan comes on mostly at full speed. It has com on a few times and booted up but then would lock up so I know there is some kind of issue. I have reseated and cleaned the processor and heatsink and still the same effect. The only thing I can think of is if the CPU or motherboard is going bad. The motherboard has the yellow/amber light inside lighted up but I do not know if that is a problem or a normal circumstance. So any help solving the problem would help either if its for sure the cpu or motherboard or some thermal issues I have missed.

Answer : Problem: Dell Optiplex fan and thermal issues

if it does not start, you can try this : start with the minimum :
mobo+ cpu + 1 ram stick, video card, PS  -->any display? If N it is one of the connected; try swapping Ram, video card, PS.  leaves only mobo & CPU.
also, inspect the mobo for bad caps :  www.badcaps.net
You can also test devices on another PC.
Also check you did not dislodge a cable by cleaning the PC.
Most probable causes : PS - and mobo