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A/C blowing @ different temps from vents..

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heat vent
73K views 86 replies 38 participants last post by  mr_y82 
#1 · (Edited)
I figured that Id get my car ready for summer today and found that my air condition was blowing at different temperatures. The side vents blow colder than the center vents.
I want to see if it was something that i might have missed before I send it to the dealership. Air is set to recirculate, knob is turned to blue, and the a/c button is on.

Does anyone know if could be a door or valve of some kind? I took the cabin air filter assembly out and the small guard/ wall behind the engine and found the box that controls the vents but I dont know what to look for.

Thanks.
 
#7 ·
There are two common failure modes of "A/C blowing warm":

If you have warm air blowing on both sides and cold air out of other vents your Heater Control valve needs replaced as it is stuck "open" and making the heater function. This is a common failure in our cars. THE HCV is mounted onto the driver wheel well under the air intake bits.

If you have warm air blowing on the passenger side and cold air on the driver side, you have low refrigerant in your A/C loop. Two steps are required here: 1) find out where the refrigerant went. This usually needs a professionally equipped shop to do, then 2) after the leak is resolved, recharge with proper level of refrigerant.
 
#17 ·
where can i find these hoses?

If you DIY, make sure you bleed your coolant system.
thanks, will do


I had the drivers side cold and the other side warm thing happen to me. After 3 times of adding dye to the freon and not being able to find a leak my mechanic decided to tear the dash apart and see if it was the core. Turns out it was and now a few grand later i have ac :bawling:
more info about your problems. just keeping all parts in mind.
 
#16 ·
I had the drivers side cold and the other side warm thing happen to me. After 3 times of adding dye to the freon and not being able to find a leak my mechanic decided to tear the dash apart and see if it was the core. Turns out it was and now a few grand later i have ac :bawling:
 
#35 ·
Ok I just changed my HCV today and it was a pain since I had to move some parts of my super charger. But for you it is real easy to remove the air intake and then pull up the HCV and loosen the 2 hose clamp and electrical plug. Then replace and do the reverse steps. Some coolant will leak out but just top it off afterward.

Well, all this work and still didn't fix my AC problem I had already change out the final stage resistor and had the AC recharged and dye test prior to the HCV. There was no leak that can be found. My problem is when the AC auto is on, it blows warm air in the middle vents and slightly cold on the driver side and passenger. If I put just the feet, its hot as heck even with AC fully blast at 59 degrees. Its also the same when I have just the windshield on. If I have the face and windshield then its hot up top and warm at the face. But when I have the feet and face on then the face vents are cold but the feel is still hot.... WTF. Does anyone else know what I should check out next? Does any one know where the damper door are located, maybe that is stuck or not working....
 
#36 ·
the blender doors are located under the cabin filter. remove the top, filter, torx bolts, and lower tray assembly. once you pull all that out you can see it behind the firewall. Its a light yellow/whitish color with 2 outer doors.


if you mess it the buttons you'll see them move. there's also a slider towards the top of the doors that will let you un-clip the doors and remove them.
 
#38 ·
my a/c problem is that the compressor isn't turning because the clutch isn't locking. the car sat for a good while because the engine overheated and I just didn't get around to working on it. just drove the car a few miles last night and the a/c wasn't working. checked the fuses and that isn't it. maybe I have a wire I didn't connect.
 
#39 ·
I just swap out the climate control unit with my friend to see if that would fix the problem. No luck at all since it still causing heat at the feet and cold in the face. The only thing left I can think of are the motors that control the flap under the dash. I also notice that my pusher fan whines when the AC is on. Does anyone know what else I can check before I have to take it to the stealership :(
 
#42 ·
Ok I try again swapping out the AC control with Tas since he got same year as mine. This time we confirm its not it cus mine works in his car but his don't work in mine. He also notice that my fan whines very loud and that my dash outside temp was not the right temp. Mine was like 10 degrees hotter then his. Does anyone know if these added info has to do with my AC problem? Anyone else know what I should check out next?

TIA,
Charlie
 
#40 ·
I just discovered the same problem on my 325 cic today. Left side cold air, right side warm air. In addition, I can not turn off the "auto" function, so I'm wondering if something else than low coolant might be the problem. Any ideas out there? I'm considering unplugging the battery for an hour or so to see if that fixes it.
 
#41 ·
Update on my AC problem



Regarding the AC blowing warmer on the passenger side. Thanks to this forum I already knew the answer: low on freon. A friend mechanic added some (using all the proper tools to check the pressure) and that was it. It is working back as expected !

Regarding the "auto" function, I'm an idiot. I've had the car for four years and had completely forgotten what it meant. It is the function for the windshield, face, feet blowers. It is working perfectly as it should.

Lesson learned. AC blowing warmer on passenger side -> low on freon. Now I hope it won't happen again (soon anyway) which would point to a leak somewhere... bad thing.
 
#44 ·
Ivanfuzz, How did this work out? Was it an easy fix? I am experiencing same thing. AC works fine when car is cool. Once I've parked and it sits in the sun for a while, I get warm air from center vent and warm-to-cool air from side vents.

BMW is telling me they'll rebuild the entire system for $1600 (charged me $200 for diagnositics and a recharge) because they don't know what's wrong. Took it to another BMW mechanic, he recharged and added to hose ends/clamps, hoping that would fix. Another $150. Problem is that it doesn't "act" up all the time, so nobody can put their finger on it. The heater valve sounds most likely. Not sure why the "geniuses" can't figure that out.

Anyone else have any comments or suggestions?
 
#45 ·
im having the same problem with mines just earlier, cold air on the driver's side, and warm on the passenger side. and reading the replies, im hoping that it just needs to be recharged.

but, did you guys who had the same problem heard some hissing sound when the blower is on? and when i turn it off, the hissing sound is gone.
 
#47 ·
I am new to the forum but have owned my 330d (2000reg) for a couple of years. Just recently, following an inlet manifold removal and heating outlet manifold renewal, my heating system was constantly blowing warm no matter what temperature I had set. I removed the water valve (mine has the additional water heater) and found a piece of plastic preventing the valve from closing. This was removed and the valve appeared to work fine for a few hours at which point the same thing had happened. I removed the valve and this time stripped it down. The source of the plastic bits was the "additional water pump for the auxiliary heater" which had stripped all four vanes of the pump and these were blocking the water valve. I have flushed the system but am assuming that two of the vanes are still circulating so will wait a few days before fitting the new valve just in case the bits are still circulating and might damage the new one!
Hope this might point some people the right way.
Does anybody know whether you can bypass the auxiliary heater and just use a single valve?

Tony
 
#48 ·
My AC problem has been fix by Sun BMW dealer locally here. Since I had try to trouble shoot most of what I can on my own, the only thing left was let the pro look at it. They were just that, found the problem to be one of my stepper motor went bad out of the 5 in the dash. They took the dash out and also notice that the center control dial didn't turn the flap correctly to give the right air flow. They made adjustment and its all good now just in time for summer temperature.

Charlie
 
#50 ·
Hi, I've been following this forum for years but this is the first time I post. I have an intermittent problem with my AC, which sometimes blows hot air out of the upper left corner of the center vents, along with cold air, while the side vents blow out cool air. If I close the center vents, the side vents will now blow lukewarm air. If I close all upper vents, the footwell will blow out really hot air.

Here's the intermittent part: The AC always work fine in the first drive of the day. It doesn't matter how hot the weather is. Usually the problem occurs when I make multiple driving trips - one stop after another - say when you drive around town running errands. If my car has been parked for more than an hour or two, the problem usually goes away when I drive again. Have taken it to dealership twice. Of course they didn't find anything wrong; no leaking and they recharged the system. The blower control (auto or manual mode) and temperature sensors seem working fine. So I suppose it's not the final stage resistor or sensor issues. And just in case anybody asks, my center vent dial is set to 3 blue dots and my thermostat is set to 68F (and I live in warm climate).

Could it be the water valve or steppar motors? I'd appreciate any input and advice on what to look into. Thanks very much!
 
#52 · (Edited)
hshirl: I have the EXACT same issue you have. Your description was spot on to what I experience. It's been acting this way for about two years now. This year, my AC didn't start up at all though, so I decided to attack the AC. First thing I did was change the Outside temp sensor (cheap fix). This made no change.

Next my mechanic (who is a friend) vaccumed the freon, added a sealant to the system and then fully charged the system. This brought the AC back alive with kicking cold air. But then I discovered that I was back where I started. It would blow cold, but if I stopped the car for a couple of minutes I would start getting the warm air just as you describe.

My next step is going to be the heater control valve. I'm hoping it's not one of the flap motors or anything like that.
 
#53 ·
mtyson227, it's good to get to know somebody who's also trying to solve the same mystery problem.

please let me know how it turns out with the heater control valve. I haven't had a chance to do that test that others described by pinching the water line. It doesn't seem easy to reach down to where the pipes are. And I suppose the test has to be done while only when the AC is malfunctioning.

Good luck with your next steps with the heater control valve. I too hope it's not the flap motors inside the dash!
 
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