Precision T5820 won't boot and erratic behaviour please help me troubleshoot

I have had this workstation running 24/7 for over a year without any problem. One day I noticed one fan (Sys 2) ramping up and down erratically. It continued to do this for a few days. I ran Dell diagnostic software which found nothing. I updated all the critical update drivers through windows including BIOS which went without a hitch but didn't fix the problem. Then the fan started to run at full speed constantly. The diagnostic then found that the Sys 2 fan was faulty. I figured the sensor wire to the fan had failed. I tried unplugging the fan from the motherboard and when I restarted the computer I got a 1-3 error (1 amber 3 white) and no boot. I didn't look into this at the time just assumed it was because of the unplugged fan. Bought a new fan and installed it. Same 1-3 error code. Reseated RAM, tried one stick at a time in different slots, reset CMOS. Still 1-3 error. The fans all started at normal idle speed and I could here some activity from the HDD but no flashing HDD indicator on the front and no display just the error code repeating.  

I put the machine away now several weeks later after some more reading I was wondering if the BIOS had somehow become corrupted - possibly relating the recent update I did. I read that you can enter BIOS recovery on some Dells by holding control and escape at the same time until the keyboard lights come on and then releasing. I tried this. It didn't appear to go into any recovery mode that I could see but suddenly it was not throwing an error code and the HDD activity light was indicating activity like it was booting up. My happiness was short lived as there was no display and although the NIC led was indicating activity the computer did not show up on my network. The GPU is NVIDIA P2000 and I have a display port to HDMI cable connected to the monitor. I tried a different monitor but there was "no HDMI signal detected". The USB ports are getting power. 

Any ideas on where to go from here?