A/C failure & auxiliary fan

2005 BMW X5 3.0i Sport 117K miles

It’s 90 degrees outside and suddenly, my A/C’s blowing hot air. In the morning when I first drive, it works fine for the first 10 mins then warm air will start blowing again. According to BMW software tester, the auxiliary fan has failed. That fan and install can easily set me back $1000. Before i take it to the shop,
how can I make sure the connector, circuit or fuse isn’t blown instead of replacing the whole fan unit?

Even when I drive on the highway, only warm air blows. Some people tell me there should be enough force of air at a faster speed which would work like the fan. Is this correct?

Refrigerant reading was good.

...how can I make sure the connector, circuit or fuse isn't blown instead of replacing the whole fan unit?

Get a second opinion.

I assume if you had the knowledge and voltmeter to check power to the aux fan with the AC on, you would have done it.

There is not necessarily enough air movement at highway speed, especially on a hot day, to keep the condenser temperature and pressures down so those people are incorrect. It helps; maybe.

Since it’s assumed that you lack tools and expertise you may have to take them at their word. A 10 year old fan could very easily be bad as they really take a beating while running.

Jumper wires could be run to the fan as a test to see if it runs and a current draw test could be done to verify beyond all doubt that the fan motor is faulty.
If you can get a finger on the fan blade you might try to rotate it. Sometimes the fan motors fail when the armature starts freezing up in the bushings or bearings and the blade assembly may be difficult or impossible to rotate.

I agree that the condenser fan is very important for ac performance, on vehicles that are so equipped

I’ll go a little off-topic now

There was a certain Benz SUV which also had a problem with the auxiliary fan circuit. When the fan stopped working, due to a blown fuse, the pressures went up, and ac performance suffered quite a bit

The repair was slight modification of the wiring. If you replaced the fuse without the modification, it would only be a temporary cure