And here's how to check them.

With the key in position 2, press and hold both AUTO buttons for >10 seconds (it takes about 12 seconds for my car). The fan should start at full speed.

If not, press the REST button for >5 seconds, until the display changes to 1 on the left side. Press the left AUTO button until the left side reads 20, and the right side should read 10. That means that full power is demanded from the auxiliary fan. If so, report back.

If there is a fuse for that fan, I don't know about it.