[WalksOn2Wheels]

It's Texas. We're still getting temps in the 80's. So I have my a/c on this morning and something very unusual is happening.

The air is blowing cold on the lower side of the vents, but hot on the upper side. What the heck is going on? A door half open? I tried cycling between hot and cold to make sure that door was working. It did go full hot, but still did the half hot/half cold thing with the dial all the way to the cold setting. Also tried going to recirculated air and back. Still getting hot/cold from the vents. Doesn't seem like any other a/c issues I've encountered before.

Any ideas?

 

[swampX3]

FRSTCHIVE hot and cold link

>check your ac pressures etc ....this is a common one ....see below examples ....best wishes

http://www.bimmerfest.com/searchres...rums/forumdisplay.php?f=65&ss=5602j1567486j24

 

[WalksOn2Wheels]

Yeah, that was my immediate go-to and I will try that on my lunch break most likely. This just happened this morning and it seemed really odd that it would blow both hot and cold simultaneously from the same vent. Almost as if there were two separate streams of air. I'll update with a pressure check.

 

[WalksOn2Wheels]

And... It worked perfect on the lunch break. Weird. Maybe an HVAC door got hung up on startup after dropping the kiddo off and everything is working fine now.

 

[WalksOn2Wheels]

Did it again last night, but worked fine this morning. I checked the pressure last night on the low pressure side with one of those refill cans I just got for my wife's car and it read a good 35 psi. The clutch is activating on the compressor without issue. Could a faulty pressure switch not be talking to my fan correctly and not cooling the condenser enough? I've been suspect of it due to my other issues in that stupid long thread, but my A/C has always worked perfectly causing me to doubt that was an issue.

 

[WalksOn2Wheels]

Hot water control valve maybe?

http://www.bimmerfest.com/forums/showthread.php?t=669208

Could explain he intermittent issue if it was an electrical hangup.

 

[swampX3]

need both pressures

need suction and discharge pressures ...also .....the heater solenoid valve can be opened up and check in < hour

 

[WalksOn2Wheels]

Ok, I did a bit more tinkering/troubleshooting this evening. I read where you can check continuity at the two pins to see if the circuit is complete. Open circuit would be a bad part (at least as far as the motor having completely failed or not). It checks out fine. I tried reading Voltage from the plug with the dial on 3 blue dots vs 3 red dots, but my meter needs a battery. I'll probably grab one this weekend to triple check. I also checked the fuses related to the heater and a/c and all checked out.

I'm finding conflicting information on the heater control valve. Some folks say it is normally open and is closed electronically, so a failure would most likely be in the open position. But then most people who have to clean/replace the thing seem to be getting NO hot air vs. warm air when it should be cold. I guess for them it was stuck closed due to a corroded shaft?

However, I did think to cycle between the vents to see what would happen and running either the floor vents only or the defroster vents only while the a/c was on and the fan at full blast put out HOT air as if I had the heater on. In the middle/face vents, it was a mix of cold/hot air. This behavior has me suspecting the control valve, but again I seem to find the opposite symptoms for most people having that issue. Also, the a/c seems to work just fine before the car warms up, but it takes a while after it's at full operating temp for the a/c to blow warm.

But either way, it looks like I'll probably pull it out over the weekend and put voltage on it to see what happens. Something is obviously up. Would love any further input. I'm also going to check and see if anyone I know has proper a/c pressure gauges, but It's unlikely to be the compressor or charge status at this point.

 

[swampX3]

valve works both ways

>the solenoid valve can work in either direction ....depending on how the electrical design guy was feeling for that model !....so ....check yalls electrical drawings for that....lots of bmw have it normally closed....BUT some are opposite

>you can shut off the heat 100% and feel if the hoses feeding your heater core are hot going to the bulkhead

>also ......feel the solenoid by getting a volunteer to cycle the on off on the heat control

>if you get DIS57 or Rheingold they can give you heater/cooling blend door status .....very handy

 

[WalksOn2Wheels]

I decided I'd rather have the part than not and only be in there once, so I ordered a clean looking, used (claims to be tested and working) unit for 40 bucks. I read through another extensive thread and people with near identical symptoms (heat in the upper and lower vents, but warm/cool in the middle) have usually had luck with the control valve replacement, provided the IHKA wasn't on the fritz. I'll get it sometime next week and probably get to it next weekend as I'm out of town most of next week anyway. I'll report back with the results. Luckily it's FINALLY starting to cool off here in North Texas, so I should manage.

 

[swampX3]

this diy link just in

>this is generic BMW ...they show coolant draining ...BUT ....you can clamp the hoses and pop the valve out too

http://www.pelicanparts.com/BMW/tec...ail&utm_term=0_e247719183-b0775c5123-70583969

 

[WalksOn2Wheels]

Ok, so either 1) My IHKA is going out of whack or 2) I just wasted 40 bucks and 30 minutes of my life because I don't know how my a/c is supposed to work.

I tested the new and old control valve and they both worked fine. When I started the car, I put the heat on full blast to get the coolant flowing to bleed what air I had put into the system changing out the valve with the hoses clamped. I let it get to full operating temp and the heater was not blowing hot at all.

So a bit of driving and toying with the temp controls, I realize that the system is regulating the temperature even when it isn't on auto. I assumed that setting the temp on the IHKA, where the digital readout is, only came into play for the auto mode. However, with the temp set to 70 degrees, the heater would not blow hot at all. I moved it to the max of 91 degrees and suddenly, there was the hot air. Same with the a/c: I would put it all the way down to 59 and it would blow super cold. Move it to 91 and suddenly its both cold and hot at the same time.

So what's the deal? To my recollection, it never did this before. I think I've had it sitting on 70 all the time and it's never made much of a difference. Is it just because we're so close to 70 degrees ambient that it's thinking it needs to blow luke warm air to avoid making it too cold? I thought the dial on the top of the dash (you know, 3 blue for cold, 3 blue for hot) was the primary adjuster for cold/hot when not in auto mode. What gives?

 

[swampX3]

IHKA EXPLAINED....some good links/official explanation too

>technical overview....down here in the swamp where the heater side is rarely if ever used ...... loads of folks just simply forget or never ever ever learn how it works !

>most X vehicles come in with the IHKA panel set at full recirculation because the added air volume in the X vehicles prevents just a regular non recirculation setting from getting the interior cool with all the added humidity and high swamp temps.....BMW have lost many many X drive sales down here because the aircon will not freeze folks enough in the summer etc

http://www.bmwmotorsports.org/BMW_docs/X5IHKR.pdf

>the big read

https://www.google.com/search?client=safari&rls=en&q=bmw+IHKA&ie=UTF-8&oe=UTF-8

 

[swampX3]

08 owners manual and IHKA/climate control links

>start with page 68 in the owners manual attachment

http://www.bmwusa.com/Standard/Cont...ideoguid=ce755fba-02a7-412b-834a-40b5e099fc06

http://www.bmwusa.com/Standard/Content/Owner/dgh.aspx