A/C blowing warm air suddenly

[babyduke]

2005 X5 3.0i sport 117k miles

Going to work this morning it was blowing icy cold air to a point I got cold. Coming home I hear sorta hissing sound from the vent then it started blowing warm air as it's 90 degrees outside. I've never had an A/C issue during the 10+ yrs I owned this car.

What's the first thing I should check? I opened the hood but don't see anything unusual.

Sorry, I should search for old posts but I'm posting using my phone and the internet's very spotty as I'm on the road currently.

[David.X5]

What sort of tools do you have?

Put the AC on high and listen for the compressor cycling on and off.

Are all vents blowing hot or just the center?

If you have a set of gauges, measure the static pressure with the car off and then the high and low pressure with the AC running.

[David.X5]

Also check that the big electric fan in the front of the radiator is turning on when you activate the AC

[babyduke]

I don't have any special tools but the common household ones.

All vents blow same temperature air.

I turned off the car to go into the store for a bit then when started again, cooler air came out. After a couple miles, air turned warm again.

That auxiliary fan never runs.

Can cabin filter be too dirty? How do you check?

[ants_oz]

If you turn on the AC and open the bonnet (aka 'hood' in USA), you should be able to see and hear the compressor clutch engaging/disengaging as the aircon cycles.

If you cannot see or hear the clutch engaging and disengaging, then that is a place to start.

There are quite a number of reasons why it won't cycle, but best to identify if that is the actual problem first.

[upallnight]

Originally Posted by babyduke

I don't have any special tools but the common household ones.

All vents blow same temperature air.

I turned off the car to go into the store for a bit then when started again, cooler air came out. After a couple miles, air turned warm again.

That auxiliary fan never runs.

Can cabin filter be too dirty? How do you check?

AC work is very specialized, which requires special tools along with a knowledge of AC principles. Sounds like it's time to take it into a professional, or just drive with the windows down.

No, a dirty cabin filter will not prevent the AC from working.

[David.X5]

I'm guessing the aux fan is toast and that is causing high pressure condition which is tripping the safety cutoff. When it cools off, things work for a little while until it gets too hot and too high pressure again. I Would second the suggestion above that it needs a visit to a mechanic if you want it repaired. And before it blows out something else...

Sadly the fan is not cheap $300-$500 depending on where you get it) and will take some time to replace. If that is really the problem, be prepared for $800-$1000 estimate (one standard BMW increment LOL).

[upallnight]

Perhaps if you told us your actual location (X5 world is not located in our solar system), a fellow BMW owner who have BMW software can scan the X to determine if the Aux Fan has given up the ghost.

[kwalk]

Following this thread as mine is doing something similar. David.X5 hit it dead on. My center, passenger, and rear vents are blowing warm. The only one that blows cold is the driver vent. All this started when I had some work done.

[David.X5]

kwalk - if you are getting mixed hot and cold, it is a sign to investigate if the heater valves are not stuck open (another common failure) - that puts unwanted heat into the middle vents and overpowers the cold from the AC system.