'01 3L X5 - A/C cold on driver's side Hot on Passenger's side
 

Hi guys,
the title says it all, A/C blowing different temp: Driver's is cold and passenger's is warm. And yes, the temp setting is the lowest on both sides, and the temp dial on dash is set to 3 blue dots.
Any ideas why?

sounds like heater valve stuck open; i've seen the same on a recent X5 i checked out pre purchase for a friend (he opted not to buy). With a quality scan tool you can read the real-time heater core temps. If not that, a bowden cable on the temp control vane would be my next guess.

I use heat + AC all the time when it's raining out; when the car is up to temp and you have climate control holding the temp steady you should hear what sounds a bit like a heart beat as the valves open and close to the driver/passenger side of the car (with radio off of course so you can hear it). with one working the beat will not be the 'lub dub' sound but just a 'dub… dub.. dub… dub' sound as only one valve flipping on/off. The valves should be right between the engine and firewall, you can likely feel the hoses and determine one is not closing and staying hot.

Andrew, when you say a heater valve, do you mean one of the two valves from the heater control valve?

it would be weird to have one side cold from a low 'freon' situation, but define 'blows cold'… cold means it's at least 15° colder coming out of the dash than in the cabin; i usually see numbers like 40 to 50F coming out; get an actual objective reading of the left vs right side. If you have 60 and 90 that's a big difference of 40 and 90. (weak vs broken)

Yes. If one of them is stuck open you'll get the symptom you describe.

My scanner will show both the valve position and heater core temp but hand on each heater hose will tell you

What scanner do you use?
If you don't mind me asking..


Mine also blows a little hotter on the passenger side, and curiously my Volvo just started to do the same..
And I read yesterday on a Volvo forum that low charge may cause it, is not a big difference, but yes you can feel it.

Since I just replaced the X5 compressor I will report, maybe tomorrow if the new recharge, took care of the problem...

Foxwell NT-510 (520 would be the same but also covers mercedes; so get that if you also have that brand).

I HATE the idea of pulling out a computer to work on a car and hate the idea of using software written in the 20th century almost as much as I hate the clumsy operating system required to use it so I researched how I can get to most things without using the sloppy system most use.

It takes a good long time like ten minutes for a full scan but you get a very good picture of what's been acting up on your car over the past 10-17 years since the last real scan. I ran on wife's car a week ago and cleared about 15 codes mostly related to low voltage.

The 510 will activate systems and report real time values such as what's the pressure of the brake lines or temp of the heater cores.

Awesome!!

It fixed the problem for me...

Now, the reason I changed the compressor, was because it was taking some time to kick in, but when the AC was working there was a slight difference between the passenger and driver side.
But now after the new recharge the problem is gone!

Excellent! Thanks for the info.

Slight difference from weak charge is not the same as warm vs cold. The sight difference is probably just from longer and shorter paths through the dash for example. If one side has cold the other has no cold but actually warm some hot/cold control is stuck the wrong way.


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I agree, or at least that's what sounds logic to me.
I will evacuate and recharge the Volvo and see what happens, in the Volvo is more noticeable..

See this post from my old account:

https://xoutpost.com/bmw-sav-forums/...ht-thread.html

Resolution post from there:

Update: I went to my mechanic and he added most of a can of R134a. He said that it's relatively common in our drier climate to need to add refrigerant every so often. He said that after 6.5 years adding this much is not a big deal but to keep an eye on it. He also said you have to be very careful not to add too much or it will make the problem worse.

When I used the infrared thermometer after it cooled down, the reading on the console vents was ~15 F

Total cost including refrigerant: $25
Having great folks at Xoutpost.com and a good mechanic: priceless

Thanks for the help everyone!

In my quest to make the A/C blow cold air, now my compressor doesn't kick on at all...So now I have warm (hot) air on both sides. The only way to get the compressor to kick on is with my NT510, and press 'activate compressor'. So I was starting it manually to fill the refrigerant because the compressor wasn't kicking on by itself. It would run for 15-20 secs, then click off. I had hoped it wasn't compressing because the refrigerant was too low but I guess not. I don't know what to do...Now I'm hot and fed up...

'01 3L X5 - A/C cold on driver's side Hot on Passenger's side
 

Compressor won't run if low side is too low but simply apply an open can of R134a and pressure will be double the requirement. If you need to shortcut the low cut off it's likely bad wire or sensor.

I had a loose connector on my low sensor that's how I know.

The NT-510 should let you view all important parts of AC including low side pressure sensor. If that part fails you can't run AC. A piece of paperclip will fake a good sensor if you are positive of a good charge (reading of about 250 high and 40-50 low (ambient affected) (approximate values).

It's not too pricy to pick up a manifold set and the only way to properly diagnose by measuring high and low side.

I recharged a friend's Chevy Suburban with rear evaporator it calls for like 8 cans of R134A and I forced it to charge by applying 12v to the AC clutch because nothing was working. Turned out to be defective low side switch oops: my vacuum pump doesn't have an "outlet" to recover/reuse the freon so paperclip it is.

I warned him to check his pressure occasionally lest he burn up his compressor but that car has been running in Phoenix for 3 years on that charge so apparently the fix "took". (I drove that truck a couple months ago and was blown away how quick that AC cools off that big vehicle in 105°F!)

The designers put a lot of effort to keep the evaporator above 32F. 15 usually would indicate too great of a compression difference often caused by low charge.

First off, this afternoon when I was running the compressor with the NT-510, when the compressor was engaged it was very cold air that was coming through the air vents. But shortly after it kicked off, the air would get warm to hot again.

What I was doing it manually getting it going and while it was on, I'd fill it with refrigerant. It did get colder the more times I did this. And if the compressor would go on and work regularly; I'd leave you guys alone...
The other observation was that when it was working, the system needed to be really high psi compared to the 38psi or so that the experts recommend. When I have it set to 38psi, get hot air only.
See if you have any ideas guys, thanks.

Recharging a system after evacuating should be done by WEIGHT of the refrigerant, not pressure reading. Don't know where you got that 38PSI, but the low side pressure should be between 35-45 psi depending on the ambient air temp. The 35-45 low side reading is only a guide.

:iagree:

In an ordinary refrigerator, the low side can get below 32 PSI because unlike automotive refrigeration, the refrigerator needs to get below 32 degrees to form ice. A refrigerator also has a heating element to defrost the ice buildup that occurs on the evaporator coil. If your low side pressure reading is 32psi or less, you system could ice up the evaporator coil and air will not pass through the coil to give up its latent heat, but flow around the coil.

The kit that I bought has a gauge that gives the psi reading. When mine was blowing cold air, the reading was really high, like 110 psi. but I'm assuming that reading was when the compressor wasn't engaged.

You can only fill by weight after evacuating all existing "freon". It also is more or less a guide when talking about 15-20 year old cars.

100+ is entirely too high for low side. If that setup is making cool. I would bet on bad seals on the compressor and you are looking at 150 high 110 low. Not sure how it would evaporate to make cold in such a scenario but as I've mentioned low side only measuring is not very helpful for diagnosing AC problems.

The pressure will equalize hi to low when not running but 100+ is way higher than I've measured. Get a high/low reading