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A/C blowing Hot and Cold at the same time
2002 325I
I'm having an odd issue and it just started happening.
I can have the A/C running and when the dash vents are selected the air blowing from the center vents is hot, I meant HOT as if the heat was set to high, and the other two vents blow ice cold. If I select so air blows both from the dash vents and on the windshield (or on the feet) all the dash vents will blow ice cold and the others will blow HOT.
Anyone else ever experienced this? Did you find a fix?
Member
Hard to tell from your description exactly which vent is which. However, a common sign of just a low refrigerant charge is the left dash left, and the left center dash vent, will blow colder then the right center and passenger dash vents. I'd imagine it's just a low charge.
Member
Mine did this when the water valve failed. I don't remember the exact name but I controls the hot water flow to the heater core. It's right behind the airbox and about 80 bucks of I remember right.
Member
My vote is here^^^^^^^^^^^^Originally Posted by fermunky
Member
Do you have the "blend" dial on red? (the dial between the two center vents) I did that when I first got the car and never even noticed it... nice you can adjust the center vents, but a little annoying if you don't know it's there.
Member
Ditto, had the same problem when i first bought mine
'99 323i ///M front bumper~5 speed~my dream
Doin' the do
You charge A/C recently or try changing out cabin filters?
Member
I don't think it would blow hot AND cold with the dial all the way to red. Just sayin...
Member
Your right, it will still blow 38 degree air even in the red position, the only thing that dial does is bypass the heater core when the heat is on so you can get cool air, however, if the water valve sticks open, you always get the hottest available air (with the exception of turning the dial to blue which will then bypass the heater core.)
Member
Thanks guys. The dial between the center dash vents is set all the way to the blue. I'm leaning toward the water valve or some kind of blend door failure. If I have to hope for something to be bad I hope its the water valve because I don't want to take my dash apart. Sorry if my description of the vents was vague, I was having hard time tying to explain the problem myself. When I said dash vents I was referring to the set of vents that can be directionally adjusted, the ones just above the radio with the hot/cold dial in between them being the center vents and the "other two" being the one to the left of the gauges and the one to the right of the passenger airbag. It just seems odd that I can split the air between "dash" vents and the "windshield" (defrost) vents or foot well vents and all the heat will go to either the foot well or the "windshield" and all the AC will come from the "dash" vents.
Does anyone know if the power is removed from water valve will it stay closed or open? I need to check the fuse for it as well.
Member
Hey, baknblak, what was it at the end. I have the same problem and I'm thinking it's that water valve. Did you end up replacing that?
Member
I had the same problem and spent a great deal of time and effort trying to figure out what was going on. I finally replaced the hot water valve and had no improvement. Frustrated I went to my mechanic and explained what I had done. He said that after replacing some parts that the computer needed to have the fault cleared. Otherwise the car proceeds as if the part were still bad. He called it a ghost fault. So if you have replaced the valve because of a fault code. Make sure you clear the fault after replacing the part. It was a simple thing but it made all the difference on my car. Good luck!
Member
Was this fault shown by the CEL, or is it just a BMW fault stored elsewhere...?
Member
Not sure what a CEL is but the fault was stored in memory although it was not presently occuring when he read the codes from the IHKA. At any rate my previous post was premature. The hot air began occuring again and I am getting very frustrated. The AC is capable of freezing cold temperatures but not when the heater valve is opening for no apparent reason. Anyone know what triggers this valve? I can hold a screwdriver next to it and it acts as a magnet when it is closed. You can tell it is closed when the screw driver sticks to it. It is pulsing a few seconds on and ten seconds off, few seconds on and ten seconds off, repeat....When it decides to let the cabin cool down it stays on continuously. What determines the duty cycle and timing of this valve? Is it malfunctioning due to a bad sensor reading? I only have a fault indicating the valve is "shorted to B+". That tells me that occasionally I am getting a short in the IHKA and it is intermittent. Pulling my hair out!!
Ok, out of frustration I removed my IHKA from the dash -which was quite easy to do by the way. I soon determined that the connectors on the back of the unit were acting flaky. With the key on, moving or putting pressure on them created all kinds of weird behavior like the screen going blank, the fan starting up and stopping, etc. Therefore, I decided the problem must be related to these connectors on the back of the IHKA. I obtained a very small #7 torx driver and removed the four screws holding the plastic cover. With a little pulling the circuit board slid right out. Close examination of the brass rivets mounting the connectors to the board showed that they were located over circuit board traces. However they were not soldered in place. Any torque or pressure applied to the connectors could break these traces and affect these circuits. I decided to carefully solder these rivets down to hiopefully resolve any damage to these traces. It took me using my wifes reading glasses and a steady hand but the results were immediate. Upon reassembly the IHKA performed properly and the problem with heat blowing through the middle vents went away. The part number for my IHKA was obsoleted. I don't know for sure but I suspect that they changed this design.
Last edited by phoenix127; 07-04-2010 at 03:25 PM. Reason: Automerged Doublepost
Member
Thats pretty bizzare. CEL = Check Engine Light, or on our cars a Service Engine Soon light. At any rate, glad you seemed to have found your problem. To answer your question about that water valve, I would think it is partly controlled by the ambient air temp versus the temp your climate control is set to. But obviously, a shorting board can case all sorts of craziness too.
Member
Same issue here. Man I wish you took pics of that IHKA and the circuitry.
Member
My money is on bad IHKA 100%. I read a ton of threads on this problem and lots of people change the water valve first but it doesn't change anything. Knowing how many electronic connectors, sockets and wirings go bad on our cars, bad IHKA is the culprit for sure. Beside above mentioned problems, my car started behaving strangely in the wintertime as well. It would start blowing crazy hot air on AUTO even though there were no changes in the interior temperature. I'm going to try getting used IHKA and see if anything changes. I'll post if I get good results.
Member
The OP hasn't chimed in in over 9 months, not sure any suggestion is gonna help them. They've either given up, or resolved the matter and didn't follow up.
Member
Hi, Ive found this forum extremely helpful so wanted to update in case it helps anyone.
I was having HOT air and cold coming out of the ac Cold in some vents HOT in others. Horrible! Indy mechanic said it was likely the inner flap doors and that he would have to take the dash apart.
I saw a few other potential fixes mentioned in forums as well which included the one that fixed mine.
I ended up at the dealer (for other reasons) and I had them diagnose it.
They suggested the water valve be replaced.
SOLVED and ac works great now!
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