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Discussion Starter #1 (Edited)
Ok so after getting a new to me E46, had a major issue with the ventilation HVAC system. Tons of searching out there, but everyone is just throwing darts and get lucky. So after digging into the system more, this is what I have learned.

The IHKA control system is pretty advanced in the car but also at the same time easy to troubleshoot once you have it figured out. I wont go into details about the system, but it does have an auto and manual feature. As long as all systems are working properly in the car, you have freedom to override the auto system.

The system works first off the control panel (10 or 12 button are interchangeable), the system reads the ambient temperature sensor under the drivers front bumper of the car, The heater core temperature sensor and the AC core temperature sensor. Then sends a voltage amount to the Heater Control Valve (HCV) under the hood, and the fan speed is regulated by the Final Stage Blower Regulator on the left side of the glove box. a/c is a manual option to engage.

Temperature is controlled by the amount of voltage given to the HCV. It is a constant voltage that is given by the IHKA. By default the valve is open (held open with a spring internal), thus allowing hot water to circulate with the heater core. Changing the voltage changes the position of the plunger allowing more or less coolant to circulate.

The position of the air stream is directed by 5 servo motors that open the different doors allowing different vents to function. There is NOT a blend/air door in the heater box in these cars that changes the amount of hot./cold air. Again, regulated with the HCV.

A/c can be manually turned on or off.

The center dash vent has the STRATIFICATION ADJUSTER that is more or less a manual override for the center 2 dash vents



So issues that I have found:

HVAC ONLY BLOWS HOT AIR ON ALL VENTS - HVAC would be a first step there to replace. They are under $65 on ebay shipped. Second would be the Ambient Air Temperature sensor. If the sensor is missing or damaged, it tells the computer it is -40* outside, thus the IHKA only wants to warm the car. Also if the heater core temp sensor is defective, same issue

HVAC ONLY BLOWS COLD AIR ON ALL VENTS - HVAC would be a first step there to replace. They are under $65 on ebay shipped. Second would be the Ambient Air Temperature sensor. If the sensor is damaged to the other extreme, it tells the computer it is 120* outside, thus the IHKA only wants to cool the car. Also check the coolant fluid level in the system and bleed properly. Also if the heater core temp sensor is defective, same issue


HVAC ONLY BLOWS AIR TEMPS TO CERTAIN VENTS - more than like a problem with one of the 5 servo motors for the vent doors. You can access 4 from the passenger side and the last one above the drivers pedal

AC NOT COLD - first check the ambient air temp sensor, second make sure the AC compressor clutch is engaged when the system is on with a quick visual inspection under the hood, and lastly inspect/recharge the AC coolant



Seems that is the most common issues there. Very common to search and not find answers as to what the culprits are. Also be sure the battery has good voltage and as a last resort you can change out the IHKA panel as they are cheap used on Ebay.

Also check all the fuses for the Heater, A/C and ventilation system. There are about 4 of them in the fuse box there. Lastly there is the heater core temp sensors.

Hope that helps everyone! Please add if I missed anything
 

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No Heat on Drivers Side...

Thanks for the info on the system operation. I have an '02 330ci that only blows cold air out of the drivers side vents. Everything was working fine after a thermostat change then I had a water pump failure on the road dumping a large portion of the coolant. Replaced the pump and pulley, filled the system, bled everything multiple times and now have minimal heater in the car. I have unplugged the heater control valve wire to make sure the valve is open to no effect. I get warm, but not hot, air out of the passenger vents, but only cold air from the drivers side vents. Also, the center dial on the upper dash vent is not functioning properly and is bound up so need to investigate.

I need some suggestions on how the flapper doors work and how each side is isolated. It's pretty cold here and I need my heater back. Any help folks?
 

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Good info. There's also the Heater Water Control Valve (64118369805) which seems to be not getting the proper voltage in order to close.

Has anyone fixed this issue?
 

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No Heat on Drivers Side...

Thanks for the info on the system operation. I have an '02 330ci that only blows cold air out of the drivers side vents. Everything was working fine after a thermostat change then I had a water pump failure on the road dumping a large portion of the coolant. Replaced the pump and pulley, filled the system, bled everything multiple times and now have minimal heater in the car. I have unplugged the heater control valve wire to make sure the valve is open to no effect. I get warm, but not hot, air out of the passenger vents, but only cold air from the drivers side vents. Also, the center dial on the upper dash vent is not functioning properly and is bound up so need to investigate.

I need some suggestions on how the flapper doors work and how each side is isolated. It's pretty cold here and I need my heater back. Any help folks?
I also have the same issue, I want cold air in the cabin but only the driver side blows the cold air and the passenger side blows hot air. after I delete the heater valve, the passenger side only blows air without cold or hot. Mine is e46 318 ci, since there is not dual climate control on e46 it shouldn't have this problem.
 

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BMW designed the AC in the E46 to keep only the driver cool when the AC system is low on refrigerant (R134a). So, if the drivers side blows cold air but the passenger side blows warm air the AC system is low on refrigerant. This can be aggravated by a bad heater control valve. Thus valve is located in the engine compartment on the left (intake side of the engine) steel inner fender. It has 2 hoses and an electrical connector. It’s open unless it’s getting 12VDC from the climate control module in the dash. The valve can become corroded if the coolant isn’t changed every 3 years or if the wrong coolant is put in the cooling system.
 

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BMW designed the AC in the E46 to keep only the driver cool when the AC system is low on refrigerant (R134a). So, if the driver's side blows cold air but the passenger side blows warm air the AC system is low on refrigerant. This can be aggravated by a bad heater control valve. Thus valve is located in the engine compartment on the left (intake side of the engine) steel inner fender. It has 2 hoses and an electrical connector. It’s open unless it’s getting 12VDC from the climate control module in the dash. The valve can become corroded if the coolant isn’t changed every 3 years or if the wrong coolant is put in the cooling system.
Thanks for your reply. After adding R134a, my AC becomes cold again. Also, I replace my heater valve with a ball valve as well to eliminate any possibility to cause AC to blow warm air.
 

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gunner, I hope you didn’t use one of those cans of R134a you can buy in any parts store. The E46 AC system is sensitive to over and under-filling.
 
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