Xoutpost.com - AC Takes forever to blow cold.

Xoutpost.com (https://xoutpost.com/forums.php)

- X5 (E53) Forum (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/)

- - AC Takes forever to blow cold. (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/108137-ac-takes-forever-blow-cold.html)

Quote:

Originally Posted by snik (Post 1138472)

Hmmm. Like not enough oil?
Then why did it change and run great for a week before it acted up again?

Sent from my iPhone using Tapatalk

Check the above post from Wpoll. He makes more sense than I do

AC Takes forever to blow cold.

Quote:

Originally Posted by wpoll (Post 1138471)

First off, I only know enough about refrigeration to be dangerous... :bustingup

But, I see "heat pumps" (as we call domestic A/C-Heating systems here in NZ) do this all the time. When pushed hard, either heating or cooling, they freeze up the indoor or outdoor heat exchanger (depending on the phase of operation). Then they will basically do nothing until they thaw, either through ambient thawing or via operational phase inversion.

But of course, cars are a little different. My own X5 has sometimes exhibited this behaviour on long summer trips when the A/C is running for long periods. It's cooling great for an hour or two, then suddenly it stops cooling so well. But 10-15 minutes later it's icy cold again. I can alleviate this somewhat by setting the temperature a little warmer so the system isn't working so hard and it seems to occur less often. I can only imagine that the expansion valve or something is freezing up and then the system has to wait until it thaws (as it cannot reverse the operational phase as a heat pump can).

But of course, while my home town isn't actually in Antarctica, we can see it from here, and I don't use the A/C very much at all - not like folk in the US mid-west or Texas etc. So I haven't worried about this too much... ;)

Nevermind. I see what it is. It's not what I thought it was.

Sent from my iPhone using Tapatalk

I'm seeing that this expansion valve fails a bit easily.
It's cheap too. I'm guessing I can't replace it within capturing all the freon. Put the new valve, then refill the system?

Sent from my iPhone using Tapatalk

When AC works great from a cold start every time but Peters off also basically every time, that's textbook case of to little freon. The reason: with less freon it's easier for the compressor to make more of a difference between high and low pressure (eg 25 psi to 235 psi) where when properly filled the pressure difference might be 45 to 245, the cooking efficiency goes up and the evaporator gets below 32°F and ices up.

If while driving you can simply turn the AC off for 10 minutes and get cold air again and especially if it's on the order of 35-40° coming out it's a near certainly that is the problem.

Quote:

Originally Posted by andrewwynn (Post 1138477)

Does peter off. It just stops cooling. Bam. Like someone hit the AC button.
Keep driving with the HVAC off makes no difference. You have to stop as seemingly always shut the car off for a few minutes.

Sent from my iPhone using Tapatalk

The IHKA will turn off the compressor if the evaporator gets to 0 degrees C AT THE POINT WHERE THE SENSOR IS to prevent freezing. The fact that it's sensing somewhere in the middle of the evaporator and the expansion valve is sensing at the outlet of the evaporator and the mechanical variable displacement compressor is trying to maintain a differential pressure makes for some strange things to be possible. You need to have only the exact amount of R134A in the system and all components need to be working correctly to maintain the balance to have good cooling and keep the evaporator from freezing and the IHKA from turning off the compressor. As pointed out earlier even freon being low or having the wrong refridgerant can actually make the portion of the evaporator where the sensor is cold enough to signal the IHKA to shut off the compressor or freeze the evaporator enough to almost stop air flow and cooling without shutting off the compressor. One thing I have observed is that if the balance is off the drivers side dash vent will not be nearly as cold as the center vents