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Old 02-20-2011, 08:54 AM   #1
alpine86
2nd Gear Member
 
Join Date: Jul 2009
Location: toronto
Posts: 167
How to confirm if my FSU is failling? Battery drain related

How to confirm if my FSU is failling? Battery drain related

Anyway I had a battery drain problem. I parked my car like 5 days in underground garage and the battery is empty so I can't even open my car with a remote.

I just did a current leak test. Here is the photos.

When my car just opened with a remote (1.4A)



When my car just locked with a remote (before sleep mode)


When my car is in sleep mode






So 40mA is just a BMW regular current usage when it's in sleep mode which I think I don't have parasitic leak.

Now my only assumption is FSU is a fault so my blower is running when no one is in the car for few days. This leads to an empty of the battery.

Is there any ways to confirm that FSU needs to be changed?
There is no visible signs of FSU failing while I drive.

Should I take a fuse which related to a blower so even if FSU is at fault I don't get any drain?

Please help
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Old 02-20-2011, 11:58 PM   #2
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I have no idea what the pictures you showed mean as I dont know anything about electronics.

Do this test. Before shutting your car off set your HVAC to ANY temp (make sure you remember it ) and ANY speed. For example set it at 28C and 4 dashes speed. Now when you start the car the next day, if the HVAC is showing you something different then it was before you shut the car off, it'll mean your FSR/FSU is going out.

There are other things that are a tell signs of a bad FSR/FSU, like irregular or inconsistent speed.

But the test that I explained works very well, as the HVAC should return to the same setting when turned on as it was when shutting off.
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Old 02-21-2011, 01:12 AM   #3
alpine86
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Quote:
Originally Posted by new member View Post
I have no idea what the pictures you showed mean as I dont know anything about electronics.

Do this test. Before shutting your car off set your HVAC to ANY temp (make sure you remember it ) and ANY speed. For example set it at 28C and 4 dashes speed. Now when you start the car the next day, if the HVAC is showing you something different then it was before you shut the car off, it'll mean your FSR/FSU is going out.

There are other things that are a tell signs of a bad FSR/FSU, like irregular or inconsistent speed.

But the test that I explained works very well, as the HVAC should return to the same setting when turned on as it was when shutting off.
alrigh thanks for your advise. I will do that tonight.

Now I just unplugged a fuse belongs to a blower so that even if HVAC control is on there is no blow.

I will see if that helps me to prevent from the battery drain.

Your method seems very useful only if there is enough battery remain so at least I can read the numbers. Sometimes my battery totally gets drained.

0.040A or 40mA is normal current flow when the car is in sleep mode. It's for maintain a clock, an alarm and other functions and 40mA is a tiny amount of current flow which should not affect on battery.

Few years ago I parked my bimmer for 4 months and it still started the engine very well.

This is getting really annoying.
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Old 02-21-2011, 01:26 AM   #4
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Quote:
Originally Posted by alpine86 View Post
alrigh thanks for your advise. I will do that tonight.

Now I just unplugged a fuse belongs to a blower so that even if HVAC control is on there is no blow.

I will see if that helps me to prevent from the battery drain.

Your method seems very useful only if there is enough battery remain so at least I can read the numbers. Sometimes my battery totally gets drained.

0.040A or 40mA is normal current flow when the car is in sleep mode. It's for maintain a clock, an alarm and other functions and 40mA is a tiny amount of current flow which should not affect on battery.

Few years ago I parked my bimmer for 4 months and it still started the engine very well.

This is getting really annoying.
My friend had the same issue of his E46. He would come to start the car in the morning and the battery would be dead. Pinpointed it to FSR and he had to unplug the battery everytime he came home before his new FSR would arrive in the mail. He used to complain about it everytime I saw him, I can see how it can be a very frustrating situation.

Let us know how your situation turns out.
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Old 02-21-2011, 05:40 PM   #5
jetjockey
1st Gear Newbie
 
Join Date: Feb 2011
Location: Woodbridge, Ontario
Posts: 13
I did not have the battery problem with my FSU. Mine started as the fan speed fluctuating and then finally (after sevarl months) no fan at all. But the display on the control unit did not change. In other words if it showed 4 bars for the fan when I shut is off it would show 4 bars when i started back up again....just no fan.
edit.... Bentley manual has a good write up on the DIY.
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Old 03-30-2011, 12:38 AM   #6
Qube
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Join Date: Sep 2005
Location: TORONTO
Posts: 1,062
The FSU in my E39 failed twice. The first time I had the same symptoms. The second time, it just wouldn't "blow" at any setting.

Now back the first time, I did the same kind of test with a clamp meter to no avail. What I did was stay with the car for 10 minutes and then noticed the blower fan turning on by itself when the car is off when it's not venting. Bingo.
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