Greetings fellow motorists! Like others, we have been plagued with higher than normal (normal being when the car was new) AC temps. It's summer time here in Florida, and many other northern hemisphere residents have posted they are having similar problems. Granted some high AC temperatures can be caused my a myriad of other problems with the AC system, but you may want to look at this.

Like others, I have changed my expansion valve, evacuated the system, and serviced the specified amount of refrigerant, and that didn't solve my problem. Here's what I found.

Inside the air conditioning control panel (manual IHKS system), there is a beveled gear that changes the direction of the temperature control **** 90 degrees; the shaft of that gear turns the rheostat, and that signal is sent to the temperature control door servo motor. My gears had skipped a tooth. So, when I rotated the temperature control **** to full cold, the temperature control door was not commanded to the fully closed position. This partially open door position allowed hot air from the heater core to mix with the cold air coming from the evaporator resulting is a 60 degree F or higher discharge air temperature. So even if you have a nice cold 40 degree temperature at the evaporator coil temperature sensor, you still have a 60 degree + discharge air temperature at the vent.

See this video:


Today I pulled the AC control panel out of the car and took it apart. It's not a difficult task The back shell clips on, so be careful when prying up the tabs to you don't break them off. Notice there are two white marks on the temperature gear that align with the pin on the beveled gear; those are your reference marks. Again, mine was a tooth off. Oh! And don't disturb the position of the fan speed shaft, or you'll have to re-clock that too.



I made a mark on the housing adjacent to the tab on the shaft before I took it apart. After I put it back together, they don't align anymore. This was a good sign.



Now, I'm back to 0% on the temp control door when I select the full cold position. Previously, I was reading 17% on the door in full cold.



Results:

I took the car for a 10 mile highway drive; speeds ranged from 60-70 MPH. (Fan on high, recirculation door closed, temp on full cold)

Temp at the evaporator temps sensor reached a cold 40 degrees F. The temperature at the register was 41. Ambient air temp was 93.

It took me about 1.5 hours from start to finish.

Hope this helps.

K

 

Dude this is a great post! Great info. Thanks for sharing.

Now for those of us with the automated HVAC and does this fix apply? My 2008 R56 S doesnt have a wheel, just 2 buttons for more or less heat.

I guess Im gonna need to take it apart and see.

 

Lex, since you scanner was indicating 0% when the door was fully closed, you need to get that scope in the vent to make sure the door is really closed.

 

I tried. My Cernova bororscope's LEDs (plugs into computer or phone) are too weak to capture much of anything. I taped the boroscope to an 18 inch Streamlight Stylus but the Streamlight died on me. Those lights are garbage. Its the 4th or 5th one I've had repaired under warranty. ( ) But I digress.





I did see a while plastic arm moving back and forth pretty far down but until I can get a new boroscope, I cant say for sure if its working properly. I also saw a black flap up higher in the dashboard, and it moved with temp changes but its the air distribution flap. It moves if you put the heat on high with AC. (for defrosting?)


I swapped in the old evaporator thermostat and nothing changed. I did notice that as soon as you unplug the thermostat the AC turns off. So I knew its getting signal but even after being away from the evaporator for minutes it still read 41 F. Or 75F depending on which mood the AutoEnginuity software was in. Honestly I dont believe its 41 F.

With the evaporator thermostat out I could see the evaporator and I put a laser thermometer on it (see the red laser light?) and it read 77 F.






The Autoenginuity showed me nothing new today.

 

I'm going to have to read up on the automatic system theory of operation. I don't have an evaporator thermostat.

 

Are you sure you dont have one? Its there to make sure that if the evaporator reaches freezing temps, the AC turns off.

 

Lex, read up on the link below. You don't have a component called and "evaporator thermostat". You do have an evaporator temperature sensor, you are correct about it's function; it's there to shut off the compressor if the evaporator gets too cold; you don't want it freezing over. Also, with the IHKA system, there are a whole bunch of other goodies (components) in that system. For example: You have an internal temperature sensor, solar sensor, automatic air recirculation sensor, ventilation temperature sensor.

The text in the manual describes a "coolant pressure sensor" which is not to be confused with the engine's cooing system. It's the high pressure sensor as shown on page 640-8 of the Bentley service manual. It's function is to shut down the compressor if the high side pressure it too high.

https://www.newtis.info/tisv2/a/en/r...ctions/XQ4fi4h

Based on the differences of your system, I would check the function of all the doors. 1. Temperature control door, 2. air distribution door, and the fresh air/recirclated air door. The IHKA module (using the inputs from all the sensors I mentioned) can control all of those doors without your permission (so to speak). We know the temperature control door can allow hot air from the heater core into the discharge air duct, but the fresh air door can have the same effect; it can allow hot outside air into the plenum instead of recirculating the cool air inside the car. That too will result in a higher air temp at the duct outlet.

Oh! One last thing. If you disconnected components (Evap temp sensor) as described in your post with the battery connected, you probably set a DTC in the IHKA module. Make sure you clear all your codes when you're finished.

 

MKO,

You're awesome. Yes of course the evaporator temp sensor, not the thermostat. I misspoke. I installed said sensor, new, when I changed the condenser, compressor and expansion valve.

I just got off the phone with a Mini mechanic and he mentioned two OBVIOUS things I forgot to check, aside from the AC pressures of course, which are #1 thing to check. As for those pressures, he told me that Mini's should never exceed 210-220 on the high side, more like 200 and 35 on the low side. This is in contradiction to the AC tables which show pressures in the 300s on hot days. But hey, he;s the AC expert. So my pressures appear to be appropriate, even though I thought they were low.


...so, he said to do 2 things:

1. Using a laser thermometer to see the temp of the AC line going into the AC expansion valve at the firewall. It should be 40 F or so. If its not 40 or at least 50 F or lower then you know the problem isnt the blend door because your AC simply isn't cooling enough. The AC pressures (low and high) will tell you the same thing. I need to do that. DUH!

2. If you want to isolate blend doors and air proportioning doors from the equation, you can put some hose clamps pliers ( ; they come in plastic, metal, small large etc. or from Harbor Freight etc) on the small rubber hoses going into and coming out of the heater core. This will prevent hot coolant from heating up the heater core all together. If you get cold air (after confirming you're getting cold coolant into the evaporator from doing #1), you know its the blend door or proportioning door.

 

You'll have to crimp both hoses at the heater core (inlet & outlet), but that sounds logical.

From your number 1 above, the AC line going into the expansion valve from the condenser is the high side of the system. That will be very hot. You want to check the low-side line going from the expansion valve to the compressor. I'll take a picture with my thermal imager.

I don't know if your MINI mechanic is an "expert" or not, but simple physics will tell you that when you have higher ambient air temperatures, that will result in an increase in the high side pressure. Gay-Lussac’s Law states that as a temperature in a system goes up, so does the pressure & vice verca. At higher ambient air temperatures, their is more heat inside the cabin of the car. The expansion valve meters the liquid refrigerant flowing from the condenser coil into the evaporator where it absorbs all that heat and carries it away. The more heat, the higher the pressure.

 

Ya after the expansion valve is gonna be the coldest but I just installed a new expansion valve and honestly I dont remember anything after the expansion valve being accessible. Its all behind the dash.




Well he is a Mini mechanic so his practical experience is certainly extensive. But for sure the pressure tables exist for a reason. Its probably no coincidence that another BMW specialist mechanic told me he barely trusts the tables because the pressures are "all over the place" with modern cars. I didnt want to question his expertise.

 

Lex, I ran some more comparison tests for you today for your reference.

Now that I have the temperature control door issue fixed, the AC is great! 42 degrees F at the evaporator, fan high, max AC (re-circulation), 45 MPH @ 2000 RPM, ambient air temp 97.

I took a thermal image of the suction line at the compressor; if you look down, it's straight below the oil dipstick. I have IR fusion with my thermal imager, so you get two pictures at once. With the evaporator temp at 43-45 degrees, the refrigerant line temp rises to 76 degrees F by the time it gets to the compressor, but at least you can take a reading on that line with your IR temperature gun.



My low side pressure was 35 PSI, and the High side was 265-270; these are AC Pro gauges I purchased from Checker, so they are not calibrated. Again it's hot today 97! The high side pressure falls right inline with the temp/pressure chart you posted. The low side is a little low according to the chart, but the evaporator temperature is great!

 

Thanks for this info! I am getting 114 F at that same line. I just checked today. I also clamped the heater core lines which didnt stop lower the cooling temps.

I came to a realization as to why my system isnt functioning. Its think its the receiver / drier. I assumed the desiccant bag in the new condenser was a new receiver / drier because it looked like the cloth kind present in some automotive AC systems, but its probably just a simple desiccant bag meant for storage of the unit which means I need to pull the bumper and evacuate the system, pull off the condenser and install the receiver drier. WOW....I f-ed up bad. I hope I didnt destroy the compressor in the process.

I order the Behr/Hella receiver / drier unit from Amazon.
I thought the desiccant bag was something like his, which is not what the receiver / drier for our cars looks like:

 

Well, that restriction would do it. Let's hope the bag didn't rupture and send the little silica particles throughout your system. If that happened, you already know you have a lot of work to do.

 

Fingers crossed!

 

I was wrong. What was installed in the DENSO condenser was a proper drier!!! I dont why the hell I was under the impression that it was silicon desiccant to protect the evaporator before installation.That $77 condenser with drier from Rockauto is a steal. A new Behr/Hella drier costs $45!

Here is the pre-installed drier in Denso condenser, after a few weeks use:


So I ended up evacuating the system, putting a new OEM-style drier and filling the system to no effect. Its still blowing 60F. Bloody waste of time.
This new Behr/Hella OEM unit is a different from the Denso. No reason to think the Denso drier isnt totally acceptable:




The evaporator temp sensor is showing 41F according to my scanner with the new Behr/Hella drier but Im still getting 59-60 at vent. I filled the system with 50 extra grams of R134a and I'm up to 40/225-250 PSI on the low/hide at 88F which is too low. It should be 45/275. I dont know why the system isnt reaching proper pressures. If I am to believe the guys at Mini, 40 psi on low side is way too high but I dont believe that, not at almost 90F.

The cover/door to the evaporator opens all the way when I call for cold air, but Im not sure if hot air is still coming across the evaporator. Im confused at this point. I dont know what to do next.


Here is the apportioning door (blend door) followed by the evap door.

 

Based on your first picture, I would suspect contamination in your system. I wonder if you mixed refrigerant oil types or if your compressor is failing. Suggest you isolate the cause of the discoloration.

Update:

Lex, I just spoke with an air conditioning tech friend of mine. I sent him the picture of your dryer element (the black one). He suggested this:

Evacuate the system and service it with nitrogen. Let is sit for 5-10 minutes under pressure. Then pull a vacuum to 300 microns; you'll need a micron gauge in your service line. My buddy says you can find a micron gauge on Amazon. Pump the system down for 45 min. Make sure you change the oil in your vacuum pump before you begin since the contaminants in your system end up in the oil

The nitrogen gas will absorb all moisture and other non-condensibles (oil that has atomized in the system).

Repeat the pressure/vacuum cycle 3 times; then service the system with the specified amount of refrigerant.

He also mentioned that too much oil in the system, too much pressure (excessive refrigerant charge), or a restriction in the evaporator can cause the compressor to pull a liquid instead of a gas out of the evaporator; that can wash the oil out of the compressor; if that happens, you get rapid wear of the internal compressor components and the junk winds up in the filter/dryer ... kinda like what you are seeing.

Hope this helps.

 

Cant thank you enough for asking on my behalf!!!

Compressor, condenser, expansion valve are brand new. The lines and the evaporator were flushed with 3 cans of AC flush. I used PAG 46.

Where the heck Im gonna get nitrogen gas? Do you run it with N gas or just pressurize?

Maybe its too much oil. I removed 0.5 -1 oz from the system when I swapped out the drier element and I didnt replace that oil on purpose. It feels slightly cooler me thinks.

PAG oil was dripping out of the AC lines when I disconnected the condenser. Not sure if that's normal. Sign of too much oil in the system? I dont recall so much oil coming out when I pulled the old condenser. Thing is the new Sanden compressor appeared to have a negligible oil in it when I turned it upside down to measure what was inside it. After the fact I learned that your supposed to remove a bolt to properly drain it as per this video:.


So I might have too much oil in the system. How much extra I dont know because no one can tell me how much oil these damn compressors ship with. BUT someone told me the pressures would be very high if the system had too much oil in it. My pressures are actually too low.

According to this nifty chart I need to check the sight glass for bubbles:

 

NO!!! You do not run it with nitrogen gas in the system. I have an N2 tank and regulator I purchased from an internet store. I had it filled at a local shop that supplies welding (gas) tanks. I like to use the N2 to check for leaks after I change an AC component or open a system. In my opinion, It's easier to check for leaks under pressure than it is under vacuum.

I wonder if you had too much oil in you system, and then that washed the oil out of the compressor; the washed out oil settled in the condenser and or evaporator coils (as you described it was leaking out when you changed the dryer). Without oil, the compressor suffered from rapid wear and that is causing your low pressures. Also, depending on the type of compressor, if you pulled a liquid into the suction line (and since liquid isn't compressible), that may have damaged the compressor.

I just watched that video link you posted. Yep, it's a piston compressor; too much oil may have killed it.

 

Ive seen guys running an AC compressor on compressed air just to see if it worked. Youtube it.

Maybe Sanden will tell me how much oil they ship in their compressors.

These are interesting presentations by Sanden.

http://www.sanden.com/objects/Failur...sis_Web_1A.pdf

https://www.sanden.com/objects/3%20-...-%20Web_01.pdf

 

Never put compressed air in an ac system or nitrogen and run it! Refrigerant also cools the compressor, and without it, you'll burn it up.

Video says 6 ounces in the compressor.

 

YA but which model are they referring to? The rule Ive read is about 4 ounces per pound of r134a. I added 3.5=- ounces on install.

Nowhere in that information available. Not Bentley manual, not ALLDATA. Ive searched.

 

I've always removed the old compressor, drained it, measured the oil amount drained, and then serviced the new compressor with the same amount. That came out of one of my specialty AC books.

If your new compressor came with 6 ounces and then you added 3.5, that could be your problem ... say hypothetically your old compressor only had 2 ounces of oil in it because the rest of the oil was resting in other components, evap, condenser, and lines. If you added leak detection ... even more oil.

 

I found this for you

Here's the link:
https://www.newtis.info/tisv2/a/en/r...-lines/OE3AmNg

Compressor removal instructions/oil servicing new compressor:

https://www.newtis.info/tisv2/a/en/r...-lines/OETbhT0



So your condenser has 40 ml, evap has 10 ml, lines 20-40 ml. Total 70-90 ml; that's 2.3 to 3 ounces.

Called my SME again, he suggested removing the compressor and reverse flowing nitrogen through the system at the compressor inlet line to blow oil out of the evap and condenser coils. I would do that, collect the oil and record the amount.

Next, I would pull the compressor and condenser and drain them. Record the amount of oil, and post your amounts for each component. Depending on the amount you collect, I would service the compressor with oil based on what I drained from the system referencing the instructions above.

 

I drained the new compressor. Less than 1/4 ounce came out even when spinning the clutch with it upside down. The entire system was flushed and the condenser was new so there was no oil in the system. I started from an assumption of zero oil in the system and added 3.5-4 oz.

 

Didn't you say earlier that you didn't remove the drain plug as in the video? So you only drained the top end of the compressor. Couple that with your other comment that when you pulled they dryer this time you had oil draining from the condenser, and you stated that didn't happen the first time. Sounds like too much oil to me.