What liquid cooler did you use?

Try connecting the pump tach cable to the FAN_CPU motherboard header.

Howdy Professor, thanks for the quick reply! Well... I'd prefer we leave the specific components out of it if possible. Im trying to understand what the "rules" of the mobo fans are and I'll adjust accordingly.  That being said:

1. I migrated the mobo and cpu to a "cooler master haf xb" evo case
2. Replaced the RAM with 32 (16x2)g of G.Skill Aegis Series 16GB DDR4-2666 PC4-21300
3. Replaced the power supply with EVGA SuperNOVA 1000 GT 80 Plus Gold 1000W
4. Replaced the video card with ASUS NVIDIA GeForce RTX 2060 Dual Evo Overclocked Dual-Fan 12GB
5. Replaced the CPU cooler with the Corsair H100i Elite Capellix
6. I've added fans all over the place:

2 front fans that came with the case + 2 fans that came with the cooler pump are sandwiching the radiator and set to intake.

Then, I have a Cooler Master MasterFan MF200R exhaust on top of the case.
Then Corsair LL120 RGB exhaust on the back top.
Last, 2x Cooler Master Sleeve Bearing 80mm Silent exhaust fans in back bottom.

Preferably, all fans plug into the H100i's controller and the pump fan plugs into the cpu header on the mobo.  That throws an error and I've tried almost every other combo using all four fan headers. No matter what I still get the cpu fan error and this rig is running cool.

Post Body:

Howdy Professor, thanks for the quick reply! Well... I'd prefer we leave the specific components out of it if possible. Im trying to understand what the "rules" of the mobo fans are and I'll adjust accordingly.  That being said:

1. I migrated the mobo and cpu to a "cooler master haf xb" evo case
2. Replaced the RAM with 32 (16x2)g of G.Skill Aegis Series 16GB DDR4-2666 PC4-21300
3. Replaced the power supply with EVGA SuperNOVA 1000 GT 80 Plus Gold 1000W
4. Replaced the video card with ASUS NVIDIA GeForce RTX 2060 Dual Evo Overclocked Dual-Fan 12GB
5. Replaced the CPU cooler with the Corsair H100i Elite Capellix
6. I've added fans all over the place:

2 front fans that came with the case + 2 fans that came with the cooler pump are sandwiching the radiator and set to intake.

Then, I have a Cooler Master MasterFan MF200R exhaust on top of the case.
Then Corsair LL120 RGB exhaust on the back top.
Last, 2x Cooler Master Sleeve Bearing 80mm Silent exhaust fans in back bottom.

Preferably, all fans plug into the H100i's controller and the pump fans plugins into the cpu header on the mobo.  That throws an error and I've tried almost every other combo using all four fan headers. No matter what I still get the  cpu fan error and this rig is running cool.

@unclewoosha 

The number on the Fans themselves are 7FM05

If you use a 7M0F5 fan mounted somewhere else with a y SPLITTER that has the 4 wire connection going to the 7M0F5 and then the 3 wire connection going to the actual CPU fan the error will go away.

Noctua-NA-SYC1-SPLITTER Cable B07655KMKV

The 511 error is due to non pwm fan and or not enough RPM for the fan.  Dell fans can go as high as 3000 to 4500 rpm.

You are going to need a fan that passes the startup diagnostic test connected to the TOP_FAN header. Corsair LL Series fans do not pass. The Dell OEM fans pass and the Corsair ML120 Pro fan will pass. The OEM AIO cooler was drawing power from PUMP_FAN. This causes BIOS to detect a liquid cooled CPU, and it will not look for a CPU fan. Since your new H100i is drawing power using SATA direct from the PSU, BIOS is detecting your CPU as air cooled. Connecting the pump tach cable to CPU_FAN is sufficient to pass diagnostic test as a CPU fan (at least with the Corsair H60 AIO).

Drop some photos of your new rig so we can see what is going on inside.

it is not the fan header on motherboard but the type of non-Dell fan you use that can cause error.  

One R10 user reported using the fan for Dell liquid cooler:

“For my case, I used a Noctua NF-F12 PWM. After pluging my pump and the fan in the right headers, no boot error.

this thread also talks a lot about which fan does not throw the bios error.

Aurora R7, After Market Cooling - Dell Community

zoomed outheaders in top of photo and right

Thanks! I ordered this y connector and a Corsair ML120 Pro. I think this might do it because it is a PWA fan. I'll try that 7M0F5 next if this doesn't work or the problem manifest with a different fan header after I resolve the CPU_FAN.

"headers in top of photo and right" is wrong. Its left and top.