AC/IHKA High issue
 

Okay guys,

I've been experiencing this for almost 2 year now.
And still been asking here and there with no exact answer.
I used to have INPA but last year it went kaput along with the laptop.
So no possible diagnostic during this time.
Recently I've installed Ista+ on laptop for diagnostic. Still new to this software.

Issue:
After a long drive in highway, AC would blow slower and cabin feels warmer.

So today I did a test with ISTA+ hooked up to read some of the parameter.

Testing was done on the following static parameter:
1. Highway speed maintained around 100kmh on cruise control
2. IHKA was set to auto - intensive
3. Both left and right temperature knobs were set to 22C
4. Rear AC not activated
5. Ambient outside temperature of around 26-29C
6. Duration of test approximately 20 minutes

The following info were obtained at the Start of test:
1. Evaporator Temp: around 3-5C
2. Both Heater Temp: around 40-45C
3. Outlet of vent temp: around 5-7C
4. Interior temp: around 20C
5. Refrigerant pressure: around 12 psi
6. Blower bar on the car: 3 bar
7. All flaps reading was 100% except for defrosting around 20 and footwell around 50%.

During the drive, it was observed that the Evaporator Temp was increasing toward 15-16C close to the end of 20 minutes drive.
Consequently Vent Temp also raised to similar value.
Other temp reading was relatively similar.
Cabin remain around 20C
Heater temp around 45C
Blower bar: 4 bar

At the end of the test, below is observed:
1. Evap Temp: up to around 16C
2. Heater Temp: around 45C
3. Vent temp: around 15C
4. Interior temp: around 20C
5. Refrigerant press: down to 8 psi.
6. Blower bar: 4 bar, yet the amount of air blown was significantly lower compared to start of test with 3 bar.
7. All flap reading remain similar to start, except the foot flap now reduced around 30ish

Not long after the test. I used the ISTA+ to trigger blower speed up to 80% as per the available option in the software (only this is available from IHKA ECU. I could not set a custom %).
Then the blower blow harder, I could immediately noticed the difference of air being moved through the vent. Then trigger was cancelled.
Interestingly, after this trigger, Evap temp now down to around 4C and vent temp to around 7-8C. I forget to check the refrigerant pressure though.

Any idea why would the blower go slower? during this highway drive?
And why would the evap temp goes higher? I would assume it's because of the blower was not blowing hard enough even though the bar on the car show 4 bar still.

Could this be an FSR issue?

Funny thing is, after exiting the highway at the end of the test, and going home for the next 10 minutes or so, I did not notice any blower slowdown. My laptop was out of battery during this time so no reading is available.
But when I did city drive, I rarely feel the blower slowdown as well.
Maybe later i'll take another reading to compare.

Other than that, does anybody have a suggestion to do next?
I did change the compressor some times in 2014 though. Could this be a compressor issue? But since evap temp can go as low as 3-4 C during idle, I am waiving compressor issue at the moment.

Car is:
2007 4.8i with IHKA High I believe.
Thanks,

IGNORE POST BELOW: for some reason I thought I was in the e53 forum....OOPS.

To make up for my enormous goof...perhaps there's something in this e70 X5 Climate control PDF: http://www.bmwmotorsports.org/pdf/e7...%20Systems.pdf

:sorry:

Nice complex question. :)

I would suggest searching the internet for BMW tech PDF documents that center around the IHKA/climate control systems that begin with the e38...which was the first model of that generation where that newer technology was adopted by the next gen 3/5/X series (e46/e39/e52/e53).

Some of your answers may be buried in some of the info below. The IHKA (automatic climate control system) can get pretty complex...perhaps too complex in some ways. :)

http://www.bimmerboard.com/members/q...iagram%201.jpg

http://www.bimmerboard.com/members/q...iagram%202.jpg

http://www.bimmerboard.com/members/q...ir%20Flaps.jpg

Hi
Thanks. This is going to be an interesting 57paged complex Ihka bedtime reading. :)

Refrigerant pressure of 8-12 psi looks suspicious. Where is this measured? Evaporator pressure should be about 30 psi with a proper charge. Have you put a set of gages on the AC to check pressures?

Yes you're right. R134a table suggest I should be over 30 psi on the low side. This was reading from ISTA+. Maybe what I need is a charge on refrigerant. Will do that later.

Anyway, yesterday I played with ISTA+ again at home and found out that by manipulating the back pressure flap opening, I could sort of recreate the feeling of slow blow in the car. Now why this is happened during drive, I still could not find the reason why on the pdf above. My guess is, it's supposed to compensate the pressure coming from fresh air intake. Because that is the logical reason. Drive fast in the highway, fresh air ramming harder than when you're in the city driving slower. Now why it closes the flap so much that I would feel the air less blown from the vent is yet to be answered.

Is it related to refrigerant pressure? To be tested later.

Okay found something interesting today while changing outside fresh air filters.
Both fresh air and back pressure flap are at 0%, but both are fully open.
Did readdress with ISTA+, still the same. Is this normal?
Thing is, for vent flap, it's the other way around, 100% for full open (at least that what I assumed when the air blowing from the vent at 100% value).

Still haven't gone to AC shop to check pressure.