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2004 BMW 325i heat and A/C blowing out of vents. #4509298
09/06/17 05:27 PM
09/06/17 05:27 PM
Joined: Apr 2016
Posts: 815
Specific Ocean
Kibitoshin Offline OP
Kibitoshin  Offline OP

Joined: Apr 2016
Posts: 815
Specific Ocean
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.


Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L
02 Chevy Silverado C1500 V8 5.3L
Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin] #4509301
09/06/17 05:28 PM
09/06/17 05:28 PM
Joined: Jun 2003
Posts: 18,419
Deplorable in apple valley, ca
Chris142 Offline
Chris142  Offline

Joined: Jun 2003
Posts: 18,419
Deplorable in apple valley, ca
clamp off the heater hose. see if that helps.


02 Wrangler carlube 5w30
87 F250 traveler 15w40
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Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin] #4509334
09/06/17 06:08 PM
09/06/17 06:08 PM
Joined: Oct 2002
Posts: 37,051
Great Lakes
Quattro Pete Offline
Quattro Pete  Offline

Joined: Oct 2002
Posts: 37,051
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


'02 530i (Edge 0W-40)
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Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin] #4509600
09/06/17 11:10 PM
09/06/17 11:10 PM
Joined: Nov 2012
Posts: 234
NorCal
Seventh Offline
Seventh  Offline

Joined: Nov 2012
Posts: 234
NorCal
Sounds like a bad heater valve to me. I'd start there.

Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Chris142] #4509614
09/06/17 11:47 PM
09/06/17 11:47 PM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline
Merkava_4  Offline

Joined: Jan 2007
Posts: 17,501
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 ?

Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Merkava_4] #4509636
09/07/17 12:29 AM
09/07/17 12:29 AM
Joined: Apr 2016
Posts: 815
Specific Ocean
Kibitoshin Offline OP
Kibitoshin  Offline OP

Joined: Apr 2016
Posts: 815
Specific Ocean
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.


Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L
02 Chevy Silverado C1500 V8 5.3L
Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin] #4509640
09/07/17 12:45 AM
09/07/17 12:45 AM
Joined: Nov 2012
Posts: 234
NorCal
Seventh Offline
Seventh  Offline

Joined: Nov 2012
Posts: 234
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.

Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Seventh] #4509642
09/07/17 12:59 AM
09/07/17 12:59 AM
Joined: Apr 2016
Posts: 815
Specific Ocean
Kibitoshin Offline OP
Kibitoshin  Offline OP

Joined: Apr 2016
Posts: 815
Specific Ocean
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.


Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L
02 Chevy Silverado C1500 V8 5.3L
Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin] #4519912
09/19/17 12:28 AM
09/19/17 12:28 AM
Joined: Apr 2016
Posts: 815
Specific Ocean
Kibitoshin Offline OP
Kibitoshin  Offline OP

Joined: Apr 2016
Posts: 815
Specific Ocean
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.

Last edited by Kibitoshin; 09/19/17 12:30 AM.

Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L
02 Chevy Silverado C1500 V8 5.3L
Re: 2004 BMW 325i heat and A/C blowing out of vents. [Re: Kibitoshin] #4520121
09/19/17 09:18 AM
09/19/17 09:18 AM
Joined: Apr 2017
Posts: 1,520
Ontario, Canada
mightymousetech Offline
mightymousetech  Offline

Joined: Apr 2017
Posts: 1,520
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.


Mighty Mouse Tech
BMW Tech, Former Acura Tech
2010 Civic Si Castrol 0W40, Redline MTL
2013 BMW 135i M Sport Edition Castrol 0W40, Redline MTL
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