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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 07-12-2011, 08:58 PM
Toimaster Toimaster is offline
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E39 Climate Control Problem

Hello, I'm a newbie! Thanks in advance for anyone that can offer guidance.

While driving with the temperature setting set for cold air (between 60 and mid 70’s), and the snowflake button activated, sometimes the air goes warm; not as warm as if the heat were on, but as though the A/C were not on, and ambient air were blowing in through the vents, warm Texas air. This phenomenon occurs in a variety of conditions: while idling in park, while driving around town… the only time it doesn’t seem to happen is when I am at highway speed. In fact, when I get off the highway and begin driving through town, the air goes warm within a minute, nearly every time.

With all of this said, what I believe is the a/c condensor fan runs at high speed after the engine is started. It sounds like the car is about to take off!

- I have replaced the temp sensor on the lower radiator hose
- I have checked the A/C, the psi cycles low and high for the 10 seconds the fan turns off every now and then.

Can anyone help me please?!?
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  #2  
Old 07-12-2011, 10:54 PM
safety glasses safety glasses is offline
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Make sure the dial between the middle vents is at the white line or into the blue and not in the red.

Hope this helps!
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  #3  
Old 07-12-2011, 11:33 PM
granlund granlund is offline
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Also make sure the dial is NOT set at three blue dots. There is a thread here somewhere on climate control settings that describes the phenomenon as 'warm burping' when the system is set to max cold.
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  #4  
Old 07-12-2011, 11:53 PM
JimLev JimLev is offline
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[QUOTE=Toimaster;6187647]Hello, I'm a newbie! Thanks in advance for anyone that can offer guidance.

… the only time it doesn’t seem to happen is when I am at highway speed. In fact, when I get off the highway and begin driving through town, the air goes warm within a minute, nearly every time.

With all of this said, what I believe is the a/c condensor fan runs at high speed after the engine is started. It sounds like the car is about to take off!
QUOTE]


Sounds like the aux fan may not be running all the time allowing the condenser coils to get too hot. You said while driving on the highway it always cools fine. At highway speeds you have lots of air cooling the condenser coil.

The temp wheel with the dots only adjusts the temp of the air coming out of that center vent.
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  #5  
Old 07-13-2011, 08:44 AM
Toimaster Toimaster is offline
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Quote:
Originally Posted by safety glasses View Post
Make sure the dial between the middle vents is at the white line or into the blue and not in the red.

Hope this helps!
The dial is at the three blue dots.

Quote:
Originally Posted by granlund View Post
Also make sure the dial is NOT set at three blue dots. There is a thread here somewhere on climate control settings that describes the phenomenon as 'warm burping' when the system is set to max cold.
I will try putting it on the white line when drive to work today.

Quote:


Sounds like the aux fan may not be running all the time allowing the condenser coils to get too hot. You said while driving on the highway it always cools fine. At highway speeds you have lots of air cooling the condenser coil.

The temp wheel with the dots only adjusts the temp of the air coming out of that center vent.
Is there a difference in the aux fan and the a/c condenser fan? On the highway/higher RPMs, it gets cold, but it still cycles to ambient air also.
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  #6  
Old 07-13-2011, 09:07 AM
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Josh P. Josh P. is offline
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Quote:
Originally Posted by Toimaster View Post
The dial is at the three blue dots.



I will try putting it on the white line when drive to work today.



Is there a difference in the aux fan and the a/c condenser fan? On the highway/higher RPMs, it gets cold, but it still cycles to ambient air also.
The aux fan is also known as the condenser fan and the pusher fan...it is distinct from the primary radiator fan. Your symptoms sound like mine, which I have optimistically diagnosed as a failing FSR (final stage resistor unit) for the A/C. Typically this causes the fan speed to drop (or go off altogether) though there are a number of symptoms that can come and go, including lack of cold air. In my case, these tend to ease, like yours, when I get on the highway. I am assuming what happens is the circuit gets overloaded in stop and go traffic, while on the highway the aux fan is not working as hard due to airflow over the condensor. (That's the theory, anyway). I have the new unit here but have not put it in yet. But it is a very common failure.

See this thread.

And also this one.
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  #7  
Old 07-13-2011, 09:10 AM
pshovest pshovest is offline
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Sounds like AC compressor is cycling, possibly due to a low charge. I would check that the AC compressor clutch is engaged during these periods of no cooling air. Clutch is engaged if, with engine running, front plate on compressor is turning at same speed as AC compressor pulley. You may need to have someone stop/start AC to see the difference.

Can you measure your vent temperatures and post?
I run my AC on 3 blue dots continuously without these symptoms.

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  #8  
Old 07-13-2011, 09:16 AM
pshovest pshovest is offline
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The FSU shown in those links has zero effect on operation of the aux/condenser/pusher fan mounted on the condenser. The FSU controls the HVAC fan for the interior of the car.

Paul S
BMW CCA 69606

Quote:
Originally Posted by Josh P. View Post
The aux fan is also known as the condenser fan and the pusher fan...it is distinct from the primary radiator fan. Your symptoms sound like mine, which I have optimistically diagnosed as a failing FSR (final stage resistor unit) for the A/C. Typically this causes the fan speed to drop (or go off altogether) though there are a number of symptoms that can come and go, including lack of cold air. In my case, these tend to ease, like yours, when I get on the highway. I am assuming what happens is the circuit gets overloaded in stop and go traffic, while on the highway the aux fan is not working as hard due to airflow over the condensor. (That's the theory, anyway). I have the new unit here but have not put it in yet. But it is a very common failure.

See this thread.

And also this one.
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  #9  
Old 07-13-2011, 09:46 AM
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Quote:
Originally Posted by pshovest View Post
The FSU shown in those links has zero effect on operation of the aux/condenser/pusher fan mounted on the condenser. The FSU controls the HVAC fan for the interior of the car.

Paul S
BMW CCA 69606
Hmm. Well even so, it still sounds to me like his issue is with the HVAC fan, not his aux fan, hence FSU.
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  #10  
Old 07-13-2011, 09:50 AM
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QSilver7 QSilver7 is offline
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Quote:
Originally Posted by granlund View Post
Also make sure the dial is NOT set at three blue dots. There is a thread here somewhere on climate control settings that describes the phenomenon as 'warm burping' when the system is set to max cold.
Just to expound more on this topic.. the phenomena of very cold air flowing down the front of the dash and being drawn into the IHKA panel's thermistor (inside the left vent on the IHKA)...which then makes the IHKA think that the air in the cabin is colder than what it is....this causes the HVAC system to send warm air thru some of the other vents to adjust the interior's temp to the setting displayed on the IHKA control panel.

See the info below...and make sure that the center dash vent is blowing air upward...and is not flowing down toward the IHKA panel (which is how the "less than 3 dots" setting came to be)

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  #11  
Old 07-13-2011, 09:52 AM
cn90 cn90 is offline
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I agree with Josh that this is likely a failing FSR.
It fails intermittently then altogether.

If you ever replace the FSR (a 15-min job), use only BMW brand.
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  #12  
Old 07-13-2011, 10:54 AM
pshovest pshovest is offline
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Fascinating. OP says air gets warm. OP doesn't say air stops blowing. Concluding this is a FSR/FSU problem is not supported by the symptoms reported.

Paul S
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Quote:
Originally Posted by cn90 View Post
I agree with Josh that this is likely a failing FSR.
It fails intermittently then altogether.

If you ever replace the FSR (a 15-min job), use only BMW brand.
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  #13  
Old 07-13-2011, 11:23 AM
Toimaster Toimaster is offline
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Can the FSR cause the HVAC fan to sound like a jet about to take off?
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  #14  
Old 07-13-2011, 11:58 AM
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Josh P. Josh P. is offline
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Quote:
Originally Posted by pshovest View Post
Fascinating. OP says air gets warm. OP doesn't say air stops blowing. Concluding this is a FSR/FSU problem is not supported by the symptoms reported.

Paul S
BMW CCA 69606
In troubleshooting, it's generally best to address the most common thing (which in this case also happens to be the cheapest and easiest to fix) first.

By most reports, a failing FSU causes all sorts of problems: no fan, inability to control the fan function, only low but not high speed, and lack of cold air (I would describe it as cool but not cold air). I have experienced all of these symptoms, which is why I am replacing the FSU. If that's not the cause of my issues, then I will chalk it up to preventive maintenance and keep looking.

For the OP, since his symptoms generally (if not exactly) mimic those of others who have had this issue, replacing the FSU seems to me to be the obvious first step. It's a part that is known to fail.

No one is saying that is definitely the cause of his problem, only a likely cause. He could certainly check the AC belt and clutch as suggested.

And Toimaster: Yes, at high speed the aux fan is very loud. Normal vehicle function.
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  #15  
Old 07-13-2011, 12:08 PM
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Josh P. Josh P. is offline
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Quote:
Originally Posted by cn90 View Post
I agree with Josh that this is likely a failing FSR.
It fails intermittently then altogether.

If you ever replace the FSR (a 15-min job), use only BMW brand.
Cam, this is true, but see this thread about replacement FSU.

There is a new design with many more pins, which is sold by EAC and Autohaus, that is brandec OEM/Behr. However, as I noted in that thread, mine is branded " Behr Hella" yet also "Made in China."

I hope Behr is not outsourcing to China but it looks that way. Autohaus typically sells reputable parts and this is the only FSU they offer for our cars.
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"Mods": driveshaft, cooling system, Vanos, CCV, PSR, VCG, FSU, spark plugs, buncha belts-n-hoses, & other things I'd just as soon forget

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  #16  
Old 07-13-2011, 12:46 PM
cn90 cn90 is offline
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Quote:
Originally Posted by pshovest View Post
Fascinating. OP says air gets warm. OP doesn't say air stops blowing. Concluding this is a FSR/FSU problem is not supported by the symptoms reported.

Paul S
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I never concluded.
I only suggested to the original poster what potential culprit is.
This is why I used the word "likely" in my post above.

I have looked into the circuitry of the FSR, it has a rather complex circuit. So the symptoms that Josh mentioned above are all possible.

Last edited by cn90; 07-13-2011 at 12:48 PM.
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  #17  
Old 07-13-2011, 05:44 PM
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I just put in the new one. PITA, contortion-wise, but an easy fix. Starless's DIY is good, and very helpful, but I would only add that glovebox removal is totally unnecessary. Pulling the lower plastic panel off gives easy access. Getting the connector out was a b!tch: my existing FSU would not pull all the way out of the socket because there was no slack in the wiring, so I couldn't get it out first before removing the connector, which is the easy way, if you can get it out.

So far, the A/C is working properly. But I've only driven a few miles. Will report back in a few days.
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OEM M5 bumper, 40% Huper Optik ceramic tint, Dice Silverline Pro iPod adapter, 540SP radial spokes, Zimmerman Z-Coat rotors w/ Hawk HPS pads
"Mods": driveshaft, cooling system, Vanos, CCV, PSR, VCG, FSU, spark plugs, buncha belts-n-hoses, & other things I'd just as soon forget

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Old 07-13-2011, 07:17 PM
Toimaster Toimaster is offline
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Thank you everyone for your suggestions. Josh, I look forward to your report!
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Old 07-17-2011, 08:06 AM
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Update:

After 500 miles, the A/C is now working properly in all situations with new FSU installed.
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OEM M5 bumper, 40% Huper Optik ceramic tint, Dice Silverline Pro iPod adapter, 540SP radial spokes, Zimmerman Z-Coat rotors w/ Hawk HPS pads
"Mods": driveshaft, cooling system, Vanos, CCV, PSR, VCG, FSU, spark plugs, buncha belts-n-hoses, & other things I'd just as soon forget

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Old 07-20-2011, 07:50 AM
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Josh P. Josh P. is offline
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I have some new information, via the parts counter at the stealer. I asked to see the FSU, using Starless's part #. He brought out an FSU with an aluminum housing, which looks exactly like the one Starless used. Then, after asking exactly what car it was for, he said that was the "old one" and brought out the correct one, which looks EXACTLY like the one I bought from AutohausAZ, except (wait for it) it was labeled Sitronic/Valeo, made in Germany. The cost was $116 (versus the $52 I paid). It shares the part # that is in the image I posted above. He noted that all their electronics are made in Germany, and that any Web site/supplier can claim OEM if the part will work. He said the part was never made by Behr. Uh oh.

I will post an image of the label later today.
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2001 530 Steel Blue Metallic, purchased Dec 03
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OEM M5 bumper, 40% Huper Optik ceramic tint, Dice Silverline Pro iPod adapter, 540SP radial spokes, Zimmerman Z-Coat rotors w/ Hawk HPS pads
"Mods": driveshaft, cooling system, Vanos, CCV, PSR, VCG, FSU, spark plugs, buncha belts-n-hoses, & other things I'd just as soon forget

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