What to do if your 7020/9020 MT board has no Thermal Sensor
If you buy a barebones Dell MT or buy just the motherboard you may or may not get the thermal sensor (thermistor) that connects to the motherboard. I searched everywhere on the internet and can't find anything anywhere. I bought the one intended for the 7010/9010 models and it didn't work at all. Not sure how Dell made something this simple be proprietary. Without this sensor the CPU fan runs at about 2,700 RPM all the time and is way too noisy for comfort.
So what did I do ? You really need just two things at the cost of about $18 to $24 USD. You need the 5 pin to 4 pin fan adapter and a third party CPU cooler from either CoolerMaster or Thermaltake. Here's the i50 CPU cooler/fan from Newegg.com. Don't worry that the seller is based in Hong Kong, they ship to you very quickly. See below.
https://www.newegg.com/cooler-master-air-cooler-series-i50/p/13C-000X-002T6?
Even if you have the Dell thermal sensor and didn't get a CPU fan in very good condition, you can still replace it with the i50 or even the
i70 from CM if you need a higher CFM (37 vs. 34) for more airflow to cool your CPU. You won't even need to buy separate thermal paste as it is pre-applied to the CM cooler.
The Hyper 212 Evo has a similar fan and is the best selling cooler in the world. Good price to performance ratio. Fan is quiet too. Not so easy to install though. It won't work on these Dell boards.
To get the i50 for about 14-15 USD is an even better deal. You can't use the 212 on the Dell 7020/9020 board. The i50 CPU cooler does fit into the existing Dell metal backplate with no problems. The backplate is
not easily removable (thanks again Dell) if you try, you may damage the board, seriously, as in beyond repair.
I expected this to take a week or more to receive it from Hong Kong. It got here in just 3 days. Don't know how they did that. I didn't pay a nickel for shipping, it was free. May have just been in a warehouse in NJ.
Why do this ? Even if you can find the 7020/9020 Dell thermistor cable the seller will charge you at least 15 dollars, probably a lot more for it anyway. The odds are you won't find one. The CM fan has bigger blades which are much quieter, even when it runs at the same speed as the OEM Dell fan.
The 5 pin to 4 pin adapters can be found on Ebay. Chinese sellers sell them for about a dollar each. US sellers about 5 dollars each. I didn't want to wait 5 or more weeks to get one from China so ordered from a US seller.
Here's an alternative black sleeved option to adapt the 5 pin fan headers to 4 pin PWM:
https://www.amazon.com/dp/B0871P9X72/?tag=tonymacx86com-20
Here's the CPU temps I'm getting on a 7020 MT system with Windows 10. It averages around 24 to 25 degrees C. Only has the CoolerMaster heatsink + CPU fan and rear exhaust fan. So pretty good cooling.
If you do want a 4 pin fan for your CPU Cooler this from Thermaltake will work well. I've used these with Dell motherboards and the 5 pin to 4 pin adapter. I think the CM fans are slightly quieter, not by much.
Buy Thermaltake Gravity i2 95W 7-Bladed 92mm 4-Pins PWM Aluminum Extrusion CPU Cooling Fan for Intel Core i7/i5/i3 CLP0556-B with fast shipping and top-rated customer service. Once you know, you Newegg!
www.newegg.com