XPS 8960, fan error with replacement case fans

"I am getting fan startup errors with my replacement case fans."
Did you replace the original OEM fans with the same OEM fans or use replacement retail fans?

I am not sure that the Dell OEM BIOS ever had a fan setting. We can see the OEM BIOS settings starting on page 73. The Dell OEM BIOS is tied to our OEM motherboard ports and fans (front chassis, rear chassis, CPU).

What speed fans did you replace the DELL fans with? Typically even with High CFM fans, you need to hit the Dell "minimum speed threshold" to get it not to fail the Uefi firmware fan check.  For example, most fans have 2400+ RPM High CFM will pass the System Case Fan check, and most CPU fans 2000 or above will pass the CPU one. 

Now failing the fan check isn't a bad thing, it just means that the firmware doesn't like your fan's rated speed, not that it won't work.   I know from experience, that I replaced all of the DELL fans in my Dell system with fans from Scythe and Nactua. Took me some trial and error to find fans that passed the DELL fan speed check. 

@JamieLinux​  Can you share which brand fans you go to work. I have tried 2 sets.

@USAF-MEDIC​ Scythe fans at least all the ones I have used 92mm and 120 and so forth seem to pass the Dell check. I have had intermittent issues with Noctua fans, mind you even if it fails the fan check the fans will still work. The failure just means it doesn't conform to what DELL expects. 

Some people reporting no issues with Noctua or Arctic Cool fans, tbh it varies based on the motherboard. 

On my Dell setup, I am using a Scyth 120mm front panel fan and a 92mm scythe exhaust fan. CPU fans 2 120mm Noctua. I do not have issues and it passes all Dell hardware tests. 

@USAF-MEDIC​     I know people have had some success with Arctic P12 Max PWM case fans

TBH get a few of each see what works and return the ones that don't we can tell you what we had success with. But to be honest, it really comes down to what board revision you have.