Fan full speed, no LED

[zedtvl]

Hi Before selling it I wanted to clean up the HDD of my late 2009 Mac mini.
It was unplugged for about a month. Last time I was using it worked fine I did a migration to the new mid 2011 model, I had it started in target mode and everything went smoothly.
It is starting the there is no LED and the fan is at full speed, I tried to reset PMU and uninstalled SMC fan control reinstalled it is still going crazy.
I do not think it is the connector since it was working fine before.
Can it be that it is due to the fact that it was unplugged for a month?
Is it true that it might be problem with the motherboard? (it starts and function depsite the fan and no LED)
Before opening it to check the connection should I do something else?
Thanks for your answers.
_________________
Mac Mini i5 2.5 GHZ, 16GB Ram.
Macbook pro 2008 Core 2 Duo, 256GB SSD, 2.5GHz, 6GB Ram
Dead PowerBook 180, M4440 33 MHz, 8 MB ram.

[zedtvl]

update:
After letting rest for 10 minutes, I started it without being attached to the monitor (a 24 inches Dell) the LED was back, the fan was normal however I had to reset the display . What was going on?
I would hate to sell a defective product
_________________
Mac Mini i5 2.5 GHZ, 16GB Ram.
Macbook pro 2008 Core 2 Duo, 256GB SSD, 2.5GHz, 6GB Ram
Dead PowerBook 180, M4440 33 MHz, 8 MB ram.

[A3man]

First of all, the PMU reset is the incorrect Procedure for your mini.
Do the SMC Reset.

When you do the PMU-Reset, the Mini starts with your fault-> No LED and Fan on Full Speed!

And after 10 Minutes letting rest, it will do the SMC-Reset and everything is ok.

Sorry for my english, i hope you understand me

[zedtvl]

no I understand very well, thanks for your answer.
_________________
Mac Mini i5 2.5 GHZ, 16GB Ram.
Macbook pro 2008 Core 2 Duo, 256GB SSD, 2.5GHz, 6GB Ram
Dead PowerBook 180, M4440 33 MHz, 8 MB ram.