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Discussion Starter · #1 ·
Hey everyone,

I’ve hit a crossroads and I’m turning to the forum. I finally bought my dream car a 2004 330i ZHP. Only downside…. I can’t get the AC to work. System holds pressure just fine and ac compressor turns on when when I hit the ac button within the car. It just blows hot air. I’m in auto tech school so I hooked it up to the service machine and I’ll be as simple with the description as possible.
-Definitely has refrigerant
-Holds vacuum
-Holds pressure
-Drained and recharged system… still nothing
whats Interesting and I can’t figure out why, the ac compressor doesn’t regulate pressure just stays on when ac button is pressed and will turn off with button depressed. I have a gauge hooked up to the low side. When the AC compressor is running is running it will just hold around 35 and when I turn it off it will climb extremely high with no regulation so I assume it’s opposite with the high side. Is there some sort of pressure regulation relay/switch that needs to be replaced? Any info is helpful thanks for your time.
 

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Super Moderator
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14,968 Posts
I enjoyed the heck out of my 8 years with my 2003 E46 ZHP. Filled up refrigerant several times but never had this kind of issue.

I moved your thread to the E46 forum, hopefully get some more exposure to try and sort this out. Best of luck with it.
 
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Nuclear engineer
02/2012 X5 35d M57Y CPO 121K miles NOKIAN WR G3 30K miles
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23,957 Posts
Hey everyone,

I’ve hit a crossroads and I’m turning to the forum. I finally bought my dream car a 2004 330i ZHP. Only downside…. I can’t get the AC to work. System holds pressure just fine and ac compressor turns on when when I hit the ac button within the car. It just blows hot air. I’m in auto tech school so I hooked it up to the service machine and I’ll be as simple with the description as possible.
-Definitely has refrigerant
-Holds vacuum
-Holds pressure
-Drained and recharged system… still nothing
whats Interesting and I can’t figure out why, the ac compressor doesn’t regulate pressure just stays on when ac button is pressed and will turn off with button depressed. I have a gauge hooked up to the low side. When the AC compressor is running is running it will just hold around 35 and when I turn it off it will climb extremely high with no regulation so I assume it’s opposite with the high side. Is there some sort of pressure regulation relay/switch that needs to be replaced? Any info is helpful thanks for your time.
BMW E46 330i Sedan / Wiring Diagrams and Functional Description / Body / Heating and air conditioning functions / Evaporator control /
Evaporator control (compressor control)

Evaporator control is activated by pressing the A/C button in the operating unit. A/C standby mode is indicated by the LED in the A/C button. If controlled compressors are installed, the cutout threshold is dependent on the outside temperature and may be between 1°C and 3°C. If a standard compressor is installed, the threshold is reduced by 1°C at high outside temperatures (> 30°C). The compressor and auxiliary fan are controlled directly by the digital engine or diesel electronics (DME/DDE). Requests for A/C compressor and auxiliary fan are sent via the K-bus to the DME/DDE. The pressure sensor also monitors the refrigerant pressure and switches the A/C compressor off if the pressure is too high or too low.

Switching conditions for the magnetic clutch:
ON: A/C button ON and evaporator temperature > 4°C (depending on the outside temperature) and coolant temperature < 117°C and terminal 30 at control unit > 9.7 Volt.
OFF: A/C button OFF or evaporator temperature < 3°C (depending on outside temperature) or blower stage 0 or coolant temperature > 120°C or terminal 15 OFF or terminal 30 < 9 Volt.

Switching conditions for DME AC idle boost:
When the A/C button is pressed, the heating/air conditioning system requests an idle speed boost via the K-bus in order to provide adequate cooling capacity at idle speed.
ON: A/C button ON and outside temperature > -10°C.
OFF: A/C button and DME_KO OFF or blower 0 and DME_KO OFF or outside temperature < -10°C and DME_KO OFF

DME_KO compressor activation:
The DME/DDE receives the instruction to switch on the compressor via the K-bus. Provided full load cutout is not active, the DME switches on the compressor via a relay. The load moment of the A/C compressor is derived from the pressure sensor signal and passed on to the DME/DDE via the K-bus.
Infinitely variable auxiliary fan control:
The refrigerant pressure in the air conditioning is registered by means of a pressure sensor and converted by means of a table into an auxiliary fan stage which is then sent to the DME/DDE via the K-bus/CAN bus. From this, the electronic engine control system then generates the control voltage for the infinitely variable fan motor .

Important!!!
New function of the IHKR46 and IHKA46 as from SW: V005.0 :
Vehicles concerned: E46 as from production break PU99 and parts from parts sales. The new software is backwards compatible. The control units must be coded.
A protection function for the compressor has been integrated in the control unit. The A/C LED flashes during initial operation and new coding of the control units. Now operate the air conditioning system for 90 seconds at idle speed. The refrigerant and refrigerator oil are mixed and distributed during this 90 second period. The A/C LED then lights permanently. This procedure avoids an excessively high start-up torque and damage to the compressor.
 

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E30 325e, E34 535i, E46 330Ci, E60 530i, F10 528i, F10 535d
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Hey everyone,

I’ve hit a crossroads and I’m turning to the forum. I finally bought my dream car a 2004 330i ZHP. Only downside…. I can’t get the AC to work. System holds pressure just fine and ac compressor turns on when when I hit the ac button within the car. It just blows hot air. I’m in auto tech school so I hooked it up to the service machine and I’ll be as simple with the description as possible.
-Definitely has refrigerant
-Holds vacuum
-Holds pressure
-Drained and recharged system… still nothing
whats Interesting and I can’t figure out why, the ac compressor doesn’t regulate pressure just stays on when ac button is pressed and will turn off with button depressed. I have a gauge hooked up to the low side. When the AC compressor is running is running it will just hold around 35 and when I turn it off it will climb extremely high with no regulation so I assume it’s opposite with the high side. Is there some sort of pressure regulation relay/switch that needs to be replaced? Any info is helpful thanks for your time.
Don't make any assumptions when you are diagnosing. Hook up gauges to both high side and low side. Record the pressures with the compressor on and off.
 

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Wingnut
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5,483 Posts
35 is around normal for the low side pressure when compressor is running. lot to keep in mind when interpreting pressures, ambient temp, vent temp etc.
with the engine warmed up and A/C off, are the vent temps higher than expected? the heater control valve could be stuck open, or if its electrically disconnected, it defaults to open, or an IKHA malfunction could be holding it open. no voltage applied to the valve opens it to flow.
when the A/C compressor is turned off, pressure will equalize tween the 2 sides, around 100 psi isnt unusual.
 

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Discussion Starter · #6 ·
35 is around normal for the low side pressure when compressor is running. lot to keep in mind when interpreting pressures, ambient temp, vent temp etc.
with the engine warmed up and A/C off, are the vent temps higher than expected? the heater control valve could be stuck open, or if its electrically disconnected, it defaults to open, or an IKHA malfunction could be holding it open. no voltage applied to the valve opens it to flow.
when the A/C compressor is turned off, pressure will equalize tween the 2 sides, around 100 psi isnt unusual.
This is my second bmw and I’m unfamiliar with the manual heat/cold selector on the vent itself and I’m playing with it trying to figure it out. My entire diagnosis I’ve had it on the cold vent setting for obvious reasons. What’s the purpose of this function if you can change the temperature anyways? I’m at work right now but to answer your question the air being blown does feel very warm even when everything is set to cold. The ac digital display/the vent. I’ll look into the heater control valve and see if that could be an issue.
 

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Discussion Starter · #7 ·
Also can someone please explain the function of the ac pressure switch on top of the dryer? Could that also be an issue if it’s faulty? The ac compressor doesn’t turn on and off and regulate pressure, but I know that’s because the temperature inside is too warm for it to kick off. Really just exploring all my options at this point.
 

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If the pressure switch hadn't worked, the AC compressor shouldn't have worked too and if AC compressor works, the blower should blow cold air, so the pressure switch is not the issue. I think there are three options - clogged AC system, broken servos/flaps in the heater module or the climate control panel doesn't work properly. Find two AC hoses that come to the cabin and check if one is hot and the other is cold. If so, it should blow out at least some cold air.
 

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Wingnut
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this thread is for the E39 chassis, but will give you an idea of how the center vent dial works, look as posts #21 and 22.
the heater control valve has 3 coolant connections, 1 input, and 2 output, one for each side of the passenger compartment. hence the 2 temp control displays on the IKHA. if youve a way to safely clamp the input hose closed ( i use a pair small of needlenose visegrips with a split piece of fuel line covering the tips, clamp lightly), this will help eliminate heater control as the problem.
for the purpose of your troubleshooting the A/C issue, set the center dial to 3 blue dots.
the A/C compressor doesnt kick on and off to regulate pressure in the system, the switch is there to monitor for out of spec condition. the compressor is controlled by the IKHA panel, dependent on the temp settings and the other controls available on it. the IKHA contains a sampling fan to draw cabin air in to it to monitor cabin temp vs setting.

edit...at your school, do you have access to a BMW compatible scanner to read the IKHA module and the flap operation for the airbox under the dash?
 
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