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#4509298 - 09/06/17 05:27 PM 2004 BMW 325i heat and A/C blowing out of vents.
Kibitoshin Offline


Registered: 04/19/16
Posts: 708
Loc: Kaiōshinkai
Got to look at my aunts 04 BMW 325i with the complaint of poor A/C so the first thing I did was check the A/C pressures at a shop and A/C pressure is within spec. This car has the fully electronic climate control system so I tried fooling around with the controls to see if the vent door actuators are working and vent positioning is working. I tried adjusting the temp to 59F (max cold) or 95F (max heat) and the air coming out of the vents still feel lukewarm. Did some googling around and it might be the heater control valve failing or in the stuck open position (powered closed when car is running) so I might proceed with that fix considering BMW's poor cooling system design.
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#4509301 - 09/06/17 05:28 PM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin]
Chris142 Offline


Registered: 06/05/03
Posts: 16947
Loc: Deplorable in apple valley, ca
clamp off the heater hose. see if that helps.
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#4509334 - 09/06/17 06:08 PM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin]
Quattro Pete Offline


Registered: 10/30/02
Posts: 35956
Loc: Great Lakes
On this vintage BMW, it could be the FSU (final stage unit), also known as blower resistor, or hedgehog...

https://www.youtube.com/watch?v=7_D-Ki_Kk2k

https://www.youtube.com/watch?v=tvVsftVT-BM
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#4509600 - 09/06/17 11:10 PM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin]
Seventh Offline


Registered: 11/11/12
Posts: 234
Loc: NorCal
Sounds like a bad heater valve to me. I'd start there.

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#4509614 - 09/06/17 11:47 PM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Chris142]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
Originally Posted By: Chris142
clamp off the heater hose. see if that helps.


Is that because the heater control valve is inline on the heater hose ?

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#4509636 - 09/07/17 12:29 AM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Merkava_4]
Kibitoshin Offline


Registered: 04/19/16
Posts: 708
Loc: Kaiōshinkai
Originally Posted By: Merkava_4
Originally Posted By: Chris142
clamp off the heater hose. see if that helps.


Is that because the heater control valve is inline on the heater hose ?


Yep. This is one of these cars that shut off coolant flow to the heater core if heat isn't needed. However I'm trying to find out if this car also uses a blend door to control the amount of heat/cold coming through the vents or it pulses the heater control valve to control heat.

After bringing the car in and pinching coolant flow to the heater core, drv. side blows kinda cold and not really cold on the passenger side vents. Returning coolant flow to heater core drv. side vent becomes warm and pass. side becomes hot so that indicates bad heater control valve. Since this car does not have a dual climate system and doesn't appear to use a heater blend door (pls. verify) it's all pointing to low refrigerant charge. The evaporator is making a loud hissing noise and other people who had the same issue pointed low refrig. charge. I'm having second thoughts with the first A/C pressure check and might bring it to my mechanic friend instead.
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#4509640 - 09/07/17 12:45 AM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin]
Seventh Offline


Registered: 11/11/12
Posts: 234
Loc: NorCal

The E46 uses a single water valve and heater core to provide
passenger compartment heat. The water valve is electrically pulsed
to control the flow of coolant through the heater core.

Temperature regulation is based on the following inputs:

-Temperature control switch setting
-Interior temperature sensor signal
-Ambient temperature signal
-Heater core temperature sensor signal
-Evaporator temperature signal
-Solar sensor input (if applicable)

Hissing expansion valve in the firewall does often indicate low charge.

Although the charge may be low, I stand by my previous statement that it needs a new heater valve. I've replaced probably a hundred of those over the years on E46/E38/E39 due to the same symptoms you're experiencing.

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#4509642 - 09/07/17 12:59 AM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Seventh]
Kibitoshin Offline


Registered: 04/19/16
Posts: 708
Loc: Kaiōshinkai
Originally Posted By: Seventh

The E46 uses a single water valve and heater core to provide
passenger compartment heat. The water valve is electrically pulsed
to control the flow of coolant through the heater core.

Temperature regulation is based on the following inputs:

-Temperature control switch setting
-Interior temperature sensor signal
-Ambient temperature signal
-Heater core temperature sensor signal
-Evaporator temperature signal
-Solar sensor input (if applicable)

Hissing expansion valve in the firewall does often indicate low charge.

Although the charge may be low, I stand by my previous statement that it needs a new heater valve. I've replaced probably a hundred of those over the years on E46/E38/E39 due to the same symptoms you're experiencing.


I guess that confirms my observations. I've ordered a new heater control valve and will double check the refrig. charge with my friend.
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01 Toyota Tundra 2WD V8 4.7L - 170k mi
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#4519912 - 09/19/17 12:28 AM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin]
Kibitoshin Offline


Registered: 04/19/16
Posts: 708
Loc: Kaiōshinkai
Update:

Shop says they recovered .56lbs of refrigerant out of system which is supposed to hold 1.6lbs. They pulled vacuum and did not find vacuum loss so they added uv dye and fully charged the system and come back if it blows warm again. A/C blows ice cold and customer and I are very happy (even for an automatic BMWs are fun to drive!)

In my original post I said the first shop checked A/C pressure. I'm guessing it's not an accurate way to determine A/C performance or the amount of refrigerant in the system.


Edited by Kibitoshin (09/19/17 12:30 AM)
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01 Toyota Tundra 2WD V8 4.7L - 170k mi
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#4520121 - 09/19/17 09:18 AM Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin]
mightymousetech Offline


Registered: 04/03/17
Posts: 1470
Loc: Ontario, Canada
Originally Posted By: Kibitoshin
Update:
In my original post I said the first shop checked A/C pressure. I'm guessing it's not an accurate way to determine A/C performance or the amount of refrigerant in the system.


It is an accurate way to diagnose if you know what you are doing.
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