Is there a reason your indy did not just plug the new fan in to test it before ripping out the old one and putting in the new one?

I literally did that last night, when finally getting around to fixing this issue on my x5 (where we live, an aux fan is not as critical as it is in most places this time of year, so I've been putting it off for a long time).

There are many ways to actively get the ECU to turn the fan on, but for me it was easiest to command the active test using my foxwell. It spun it up gradually and then held it at full speed for a while before letting it back down. Prior to buying the new fan, I tested the system thoroughly to make sure the signal was being sent, but the fan was not doing its job. There is another thread on here where I provide a ship ton of info on that.

Of course, the foxwell commands go through the ECU, so if you really do have a problem with the ECU or the wiring, failure will not be conclusive.

BTW, that fan (I got a TYC - about $150 at RockAuto.com, highly rated) is incredibly powerful. I would similarly be concerned about having it set on full speed all the time the AC is on. I joked with my kids after opening the box that I was going to install a propeller on the front of the x so it would go faster, and now realize that's not completely joking.

So if your indy could have done that test but does not have a good reason why he did not, I'd factor that into any further consideration of his advice.

Good luck.

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2001 X5 3.0i, 203k miles, AT, owned since 2014