Hi Wadus,
Thank you for posting in Microsoft Community. We are happy to help.
May I confirm the exact specifications of your Surface Pro 7?
I'm sorry but we do not have a specific tool or application to check a fan speed or detect if fans are working.
The fan of the Surface devices are equipped to adjust it's fan speed automatically based on the temperature of your Surface. The hotter the device temperature, the faster the fan's speed to help the device cooldown and perform as expected.
You may also try to change on how you want your CPU to perform, by selecting the battery icon on the task bar and adjusting the power mode. Setting the power mode to Recommended throttles the CPU and helps keep it running cooler with less need of assisted cooling. While a setting of Better performance or Best performance will allow the device to run more quickly, it will also allow the fan to come on more often to keep the CPU cool and performing it's best.
If the fan kicks in by changing the CPU performance, you should be hearing a slight sound on the device or you may feel an air coming out from the side air vents of the device.