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E36/7 Z3 (1996-2002)
E36/7 Z3 Roadster, Z3 coupe, Z3 M Roadster and Z3 M Coupe talk with our gurus here.

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  #1  
Old 09-10-2007, 12:02 AM
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dwm dwm is offline
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Z3 deleting the battery safety terminal

Some of you may remember that when I deleted the battery safety terminal to accomodate the Voltphreaks and Optima yellow batteries and my distribution blocks, I used a .1A fuse in place of the BST. Well, that gave me an airbag light that I didn't notice because my V1 remote display is in front of it and I always have red glow from behind there in the garage from the parking brake light. Doh, smack myself in the forehead.

Out of coincidence, I noticed it after I had the seats out and back in for the new fire extinguisher mounts (I put one on each seat so I can have it on either side). The Peake tool showed table 06, code 0b. There's no table 6 in the Peake manual, sigh. But in other tables, 0b is battery disconnect circuit.

Unfortunately I had thrown out my battery safety terminal because I knew I couldn't use it again and didn't want a pyro device laying around in my box of battery box parts. My notes said it read .2 ohms. Apparently my notes were wrong. The .1A fuse I used to replace the BST measured 11.4 ohms on the DMM. Apparently the SRS module isn't happy with that. I swapped in a 1A fuse that read .2 ohms and tried to clear the code, but it came back. Lovely, now I had to hunt for the right resistance.

I found a Bosch application note that showed 2 ohm loads on the pyro firing circuits. Looked at some Cooper-Bussman AGC datasheets and found the DC resistance of their .25A AGC fast-blow fuses is 2.3 ohms cold. Ah, I bought some .25A fast-blow fuses when I bought the .1A fuses. I measured them, they're 1.8 to 1.9 ohms on my meter. I replaced the .1A fast-blow fuse with a .25A fast-blow fuse, cleared the code and it didn't come back. Took the fuse out and toggled the ignition, same code came back. Put the .25A fuse back in and cleared the code again. It didn't come back.

Moral of the story... if you're going to delete the battery safety terminal, replace it with a fuse that measures about 2 ohms DC resistance. I don't know the output current for the pyro firing, but from Bosch application notes it looks like 1.2A to 3A is fairly typical. At 1.75A, a .25A fast-blow Cooper-Bussman AGC fuse will blow in less than 1/100th of a second. Why care? It's a bad idea to have an airbag light on all the time, potentially hiding an airbag problem. I can live without the battery safety terminal, but not without airbags.

Thanks to Randy for loaning me his Peake SRS tool. It's on my shopping list (LeatherZ, of course).

Cooper-Bussman Fast-Blow AGC Fuses datasheet (PDF)

Bosch CG984 4 x Firing Loop IC for Airbag Systems High Energy (PDF)
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Last edited by dwm; 09-10-2007 at 12:07 AM.
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  #2  
Old 09-10-2007, 04:57 AM
The Other Tom The Other Tom is offline
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Good Job, Daniel. Thanks for posting
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  #3  
Old 09-23-2007, 03:32 PM
sierragli sierragli is offline
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Quote:
Originally Posted by dwm View Post
Some of you may remember that when I deleted the battery safety terminal to accomodate the Voltphreaks and Optima yellow batteries and my distribution blocks, I used a .1A fuse in place of the BST. Well, that gave me an airbag light that I didn't notice because my V1 remote display is in front of it and I always have red glow from behind there in the garage from the parking brake light. Doh, smack myself in the forehead.

Out of coincidence, I noticed it after I had the seats out and back in for the new fire extinguisher mounts (I put one on each seat so I can have it on either side). The Peake tool showed table 06, code 0b. There's no table 6 in the Peake manual, sigh. But in other tables, 0b is battery disconnect circuit.

Unfortunately I had thrown out my battery safety terminal because I knew I couldn't use it again and didn't want a pyro device laying around in my box of battery box parts. My notes said it read .2 ohms. Apparently my notes were wrong. The .1A fuse I used to replace the BST measured 11.4 ohms on the DMM. Apparently the SRS module isn't happy with that. I swapped in a 1A fuse that read .2 ohms and tried to clear the code, but it came back. Lovely, now I had to hunt for the right resistance.

I found a Bosch application note that showed 2 ohm loads on the pyro firing circuits. Looked at some Cooper-Bussman AGC datasheets and found the DC resistance of their .25A AGC fast-blow fuses is 2.3 ohms cold. Ah, I bought some .25A fast-blow fuses when I bought the .1A fuses. I measured them, they're 1.8 to 1.9 ohms on my meter. I replaced the .1A fast-blow fuse with a .25A fast-blow fuse, cleared the code and it didn't come back. Took the fuse out and toggled the ignition, same code came back. Put the .25A fuse back in and cleared the code again. It didn't come back.

Moral of the story... if you're going to delete the battery safety terminal, replace it with a fuse that measures about 2 ohms DC resistance. I don't know the output current for the pyro firing, but from Bosch application notes it looks like 1.2A to 3A is fairly typical. At 1.75A, a .25A fast-blow Cooper-Bussman AGC fuse will blow in less than 1/100th of a second. Why care? It's a bad idea to have an airbag light on all the time, potentially hiding an airbag problem. I can live without the battery safety terminal, but not without airbags.

Thanks to Randy for loaning me his Peake SRS tool. It's on my shopping list (LeatherZ, of course).

Cooper-Bussman Fast-Blow AGC Fuses datasheet (PDF)

Bosch CG984 4 x Firing Loop IC for Airbag Systems High Energy (PDF)
Hi Tom, My name is James and I am in Scotland and I have just read your advise on how to Delete your B S T, and would you please tell me the best place to put the 25 fuse, as I was thinking on removing the orange generator and putting the fuse on it's blue and brown wires, or on the end of the black wires on the yellow connection at the battery safety terminal any help would be appreciated. Regards James.
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  #4  
Old 09-23-2007, 04:08 PM
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dwm dwm is offline
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Quote:
Originally Posted by sierragli View Post
Hi Tom, My name is James and I am in Scotland and I have just read your advise on how to Delete your B S T, and would you please tell me the best place to put the 25 fuse, as I was thinking on removing the orange generator and putting the fuse on it's blue and brown wires, or on the end of the black wires on the yellow connection at the battery safety terminal any help would be appreciated. Regards James.
My name is Daniel, not Tom.

That's .25A (1/4 A), not 25A. Put it across the black wires for the battery safety terminal with an in-line AGC fuse holder.
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  #5  
Old 09-25-2007, 10:05 AM
sierragli sierragli is offline
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Quote:
Originally Posted by dwm View Post
My name is Daniel, not Tom.

That's .25A (1/4 A), not 25A. Put it across the black wires for the battery safety terminal with an in-line AGC fuse holder.
Cheers Daniel , James..
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  #6  
Old 10-27-2007, 06:57 AM
mikeibr mikeibr is offline
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Bst

Hi Daniel
Hi please help
I have a 2003 530I my airbag light came on I tried to reset the light but it would not turn off i got a code it says 11 BATTERY POSITIVE TERMINAL ISOLATION 1
i fount out that the BST is bad i read you add on how to delete the BST and turn off the light.
i got .25A fuse and i am kind confuse where to place the fuse
i got a wire with a yellow connector comming from inside the car and there is a short wire with a yellow connector going from battery cable and mate toghether
where should i place the fuse
your help is greatly apreciated

THANKS
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  #7  
Old 02-02-2009, 02:16 AM
lebovitz lebovitz is offline
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Did u get answer for this? I have the same problem with my 530i.
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  #8  
Old 02-02-2009, 03:46 AM
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bob lindquist bob lindquist is offline
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I have spent much less time than you Daniel, on the electrical system in our cars. I have observed the system is not just cut and dry +12 and ground. The system seems to rely on an odd potential.

I remember measuring float voltage in the brake light circuit.

Right now I am suffering from a cruise control failure. Studying the schematics I see a challenge to fault isolate the faulty component.

Should you be poking around that circuit or have the inclination to assist, I am trying to develop a plan of fault isolating the failed component. The a8 module is quite expensive so I don't want to buy one only to find it was not the cause.
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  #9  
Old 02-02-2009, 04:53 AM
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EOD Guy EOD Guy is offline
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Bob should you fix this...... I have the same problem!
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  #10  
Old 02-02-2009, 06:39 PM
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dwm dwm is offline
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Bob, what are the symptoms? The obvious thing to check is the clutch switch.
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  #11  
Old 02-03-2009, 03:51 AM
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bob lindquist bob lindquist is offline
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symptoms.

i checked the two obvious items fuses and clutch switch.

now I am looking at the two pages of electrical diagrams in the electrical troublshooting book.

takes a bit to understand what potentials are expected where.
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Dinan suspension, M rotors /Axxis pads
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seat tilt coupling nuts, spare tire

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  #12  
Old 10-28-2010, 01:43 AM
budahkan budahkan is offline
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Hi Daniel. Is it possible if you can post a pic of the Battery Safety Terminal the way it currently looks?
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  #13  
Old 10-28-2010, 07:04 AM
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amancuso amancuso is offline
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Bob, I know your post is old, but for everyone else... In Automatic equipped cars a faulty brake light switch can cause non-operative cruise control. Even though the lights work, something in the switch is faulty.
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  #14  
Old 10-28-2010, 08:47 PM
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dwm dwm is offline
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Quote:
Originally Posted by budahkan View Post
Hi Daniel. Is it possible if you can post a pic of the Battery Safety Terminal the way it currently looks?
I'm not sure what you're asking. I threw the battery safety terminal in the trash over 3 years ago, hence can't take any pictures of it. If you mean the fuse I used to replace the igniter... I don't have any pictures of it and at the moment don't feel like removing my battery to take pictures of it. What do you want to know?
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  #15  
Old 09-24-2011, 01:26 AM
chapmanw chapmanw is offline
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I apologize since this is an old thread but this is the only resource I could find concerning this topic.

I also have the same question as mikeibr. Where do I place the fuse after I get rid of the BST? My BST setup is the same as post #6 http://forums.5series.net/topic/9925...1#entry1180599

Thanks in advance! If you have a diagram of your setup, it would be greatly appreciated.




Quote:
Originally Posted by mikeibr View Post
Hi Daniel
Hi please help
I have a 2003 530I my airbag light came on I tried to reset the light but it would not turn off i got a code it says 11 BATTERY POSITIVE TERMINAL ISOLATION 1
i fount out that the BST is bad i read you add on how to delete the BST and turn off the light.
i got .25A fuse and i am kind confuse where to place the fuse
i got a wire with a yellow connector comming from inside the car and there is a short wire with a yellow connector going from battery cable and mate toghether
where should i place the fuse
your help is greatly apreciated

THANKS
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  #16  
Old 01-16-2012, 10:26 AM
kennye 68 kennye 68 is offline
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airbag light

Quote:
Originally Posted by chapmanw View Post
I apologize since this is an old thread but this is the only resource I could find concerning this topic.

I also have the same question as mikeibr. Where do I place the fuse after I get rid of the BST? My BST setup is the same as post #6 http://forums.5series.net/topic/9925...1#entry1180599

Thanks in advance! If you have a diagram of your setup, it would be greatly appreciated.
I'm having same issue with an M3 .have already posted thread in m section but no replies Please help because don't want to go to stealer for repair kit !!!
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  #17  
Old 01-16-2012, 10:41 AM
kennye 68 kennye 68 is offline
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Here's link to original thread :http://www.bimmerfest.com/forums/sho...d.php?t=593327

Regards

Kenny !!!!
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  #18  
Old 09-17-2013, 04:18 AM
frankge973 frankge973 is offline
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Hello to everybody,

I drive a BMW Mini Cooper S (2003)
I have from several months, Airbag LED on and I tried to check it with diagnostics software and cable but after a while, led comes on again.
The diagnostic reports BST termnial, resistance too high.
So I think more likely that is the BST circuit but I want to avoid to change all cable coming from battery in the rear of car to the front of car (around 600 EUR). The place where battery is placed have been wet due to rain and maybe this could be the reason of fault.
I read this article, maybe that I can use the instructions here, with the fuse?
What do you think?
What I have to do precisely?
Usually I repair and check myself so I'm a little bit skilled but I've fear, I don't know what to do.
there is someone that could help me?
Thanks to all!
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  #19  
Old 09-17-2013, 05:17 PM
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Clearancediver Clearancediver is offline
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Z3 deleting the battery safety terminal

Clean all your connections... A dirty connection will increase the resistance. Had an issue with an airbag light that was due to high resistance (BMW Tech) that was cleared by simply cleaning the connection ... In this case the connection was in the battery compartment. The trunk/battery had suffered from water ingress...


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