PSU fan running at full speed

[Nathan6]

I have a 3 year old compaq pro. It's clean and doesn't work too hard. All okay until today.

Turned it on and after a minute or so the psu cooling fan started to ramp up to full speed. Then found that there was no display output to the projector it's used with.

Have cheked several times. On power up, CPU fan starts. PSU fan turns for a second or so and stops. Repeats, then runs at 'normal' speed. The hard disk spins and the LED indicates hard drive is working. No video output. Tried a VGA monitor as well, nothing. Then after a minute the fan accelerates to full speed and just keeps going. Tried blowing out what little dust was in it, un-plugged and re-plugged all the connectors. No joy. 

What's the most likely suspect?

[SHThompson]

The Memory Modules.

Try unplugging them and putting them back in first.

[Nathan6]

Are you referring to the RAM? If so, unplugged it and plugged it back in several times, even tried changing the slot. Still no good I'm afraid.

[Nathan6]

Even tried changing it for a known working module. 

still no change.

[AkshayKadam]

Hi Nathan6

I understand that your CPU works fine but monitor does not work. I shall suggest you some steps. Please try these and tell me if they work.
First of all remove the CPU side panel. On the motherboard you should see CMOS battery. It looks similar to the battery in wrist watch. Remove that battery by shifting the lock.
Now remove your RAM. You must see golden strip on your RAM. You should rub that golden strip with pencil eraser carefully. Do not touch anything else on RAM.
Now insert the RAM and CMOS battery. Power on and wait for 2 minutes and then turn on your computer.

Please try above steps and let me know what happened.

[Nathan6]

Hi Akshay,

still no change. ( Had already tried resetting the CMOS. )

I'm not entirely sure the CPU is  working.......