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dv-4177 black screen after unplugging fan for replacement

HP Recommended
HP Pavilion Dv7-4177nr
Microsoft Windows 8.1 (64-bit)

This has me stumped!

So I have an older laptop pavilion dv7-4177nr.  running Windows 8.1

It was getting pretty hot, like hot to the touch. Temperature readings hovering around 140 degrees Fahrenheit on idle. I decided to open the case and clean the fan and any other part that was dirty.

I was very careful and the disassembly went fine. I unhooked the fan wires from the motherboard and took the fan out and cleaned it. 

After the cleaning I hooked the fan wire back up and reassembled the laptop making sure to be  very careful.

Once it was all back together I turned it on and it booted and started windows normally.

After a while of letting it run I did notice the temperature went down a few degrees. Well I wasn't satisfied with that temperature reading after all the work i did taking it apart and putting it back together...

So I decided that I was going to put in a bigger 12volt fan and run it from a separate power adapter. In order to do this I had to cut the bottom air vent larger to accommodate the new fan size. 

Once I had that done and the fan installed and externally attached to the bottom of the laptop blowing in, I put it all back together again.

 

Now this is where it gets weird....

When I turned it back on all I got was a black screen. The caps lock light flashed 2 times and the f12 light was on steady amber color...After about 15 seconds it shut itself down.

I looked up the light codes on HP support and it said it was a BIOS corruption failure.

So I followed the steps it suggested...

Nothing has worked.

Hard reset did nothing...

Windows+ B or windows+v did nothing

Reseating the RAM did nothing.

All I get is a black screen and a shutdown...

So I hooked up an external monitor and the laptop started and showed only on the external monitor. It immediately went to an error screen.

It said...

System fan (90b) The system has detected that a cooling fan is not operating correctly. The system will shutdown in 15 seconds.

I pressed enter and it booted up windows.

Now the new fan I installed is NOT hooked up to the motherboard. It is plugged into a 12 volt power supply.

New temperature readings say 115 degrees  Fahrenheit. Down from 140 degrees. That's a 25 degree difference!!

But the laptop screen is still black! I even checked the wire connections to the screen and they look good. I have no idea whats going on! can anyone out there help me?

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