Just curious: What is the purpose of the three relays in the trunk battery box? - Bimmerfest - BMW Forums



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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 09-21-2011, 07:00 PM
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bluebee bluebee is offline
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Just curious: What is the purpose of the three relays in the trunk battery box?

Just curious what the purpose of these three relays in the trunk battery compartment is ...



The realoem diagram didn't help much:



I also looked in Realoem control units, modules, sensors, relays:




So, the colors, apparently, such as "pine green", indicate the 'type' of relay; but it still doesn't say what accessory the relay handles.

Do you know what component these three relays handle?
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Last edited by bluebee; 09-21-2011 at 07:08 PM.
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  #2  
Old 09-21-2011, 07:51 PM
solera solera is offline
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it depends on the type of DME you have, for example the further most left is probaly for the fuel pump
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  #3  
Old 09-21-2011, 08:06 PM
JimLev JimLev is offline
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Pretty sure in '01 the fuel pump relay got moved behind the glove box.
Unloader relay, rear window defogger relay, and central locking relay.
I have 4 relays, 4th is fuel pump.
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  #4  
Old 09-21-2011, 10:31 PM
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Quote:
Originally Posted by JimLev View Post
Unloader relay, rear window defogger relay, and central locking relay
Interesting.

Unloader relay.

Never heard of it.

Searching ... I find:
- What in His name IS the unloader relay?
Quote:
The Unloader kills power to the electrical system when the car is in start position ( cranking )
- Unloader Relay ????
Quote:
Unloader relays cut power to all but necessary electrical items when you are engaging the starter.
Quote:
Originally Posted by JimLev
I have 4 relays, 4th is fuel pump.
Does yours look like this?

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Last edited by bluebee; 09-22-2011 at 05:22 AM.
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  #5  
Old 09-22-2011, 04:28 AM
JimLev JimLev is offline
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Yup, that's mine.
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  #6  
Old 09-22-2011, 10:11 AM
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CoreyMNK CoreyMNK is offline
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Quote:
Originally Posted by bluebee View Post
Interesting.

Unloader relay.

Never heard of it.

Searching ... I find:
- What in His name IS the unloader relay?
- Unloader Relay ????


Does yours look like this?

If it kills power to all accessories while the starter is engaged, why does my radio not turn off. I've noticed this feature and greatly like it. On my other two cars, the radio turns off while the starter is engaged.
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  #7  
Old 09-22-2011, 10:15 AM
skylord skylord is offline
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if your radio turns off during start that means your switched power wire is on the accessory line instead of the ignition line.

When cranking the key your ignition system stays hot but the accessory system turns off during crank
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  #8  
Old 09-28-2011, 10:35 AM
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According to this thread today, apparently the 'fuel pump relay' is K96:
- Where is "MY" fuel pump relay? Pic inside

Quote:
Originally Posted by edjack View Post
According to Bentley, K96, the fuel pump relay, is the left-most one on that rack.
So, in the next post, I'll google for the location of K96 to see what I can find.

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Last edited by bluebee; 09-28-2011 at 12:07 PM.
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  #9  
Old 09-28-2011, 11:58 AM
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Doing a google search for K96, I find this wiki.bentleypublishers.com link:
- BMW E39 Fuel pump relay locations
  1. Home
  2. Support
  3. Tech
  4. Online Technical Library - Home
  5. BMW
  6. BMW 5 Series MY 1997 - 2003 (E39)
  7. BMW E39 Fuel pump relay locations
Location of BMW E39 fuel pump relay from 2001 onward:


Location of BMW E39 fuel pump relay up to 2001 (sedan):


Location of BMW E39 fuel pump relay up to 2001 (wagon):
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Last edited by bluebee; 09-28-2011 at 12:05 PM.
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  #10  
Old 09-28-2011, 08:36 PM
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champaign777 champaign777 is offline
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you don't need to touch K96 ( fuel pump relay ) behind the glove box which you need to remove

just remove main DME realy ( left side under salon filter ) and fuel pump will be disconnected as well

Last edited by champaign777; 09-28-2011 at 08:39 PM.
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  #11  
Old 10-29-2011, 05:22 PM
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For the record, JimLev just now showed a way to test the fuel pump relay by jumping contacts ...
- E39 (1997 - 2003) > No voltage at fuel pump connector?? E39 540i
Quote:
Originally Posted by JimLev View Post
The fuel pump relay is fused with F31, 10 amps
The fuel pump is fused with F54, 15 amps in your car.

The power to the FP is only there for a few seconds. After you turn the key to start and the engine is running power is there continuously.
Have you tried junping the contacts to keep it running without using the key?
At the FP connector brown is ground and white/blue is 12 volts from the FP relay.

This pic is from my '00 540
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  #12  
Old 02-28-2013, 11:47 PM
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For the record, I modified two of the pictures in this thread for this thread today:
- > E39 (1997 - 2003) > Picture & amperage & description of every single fuse & relay in the BMW E39


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Please read the suggested threads and add value, either by pictures or by descriptions, so the next person stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #13  
Old 01-14-2015, 02:05 AM
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bluebee bluebee is offline
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This thread today covered the various locations for E39 fuel pump relays...
> E39 (1997 - 2003) > Fuel Pump relay in 03 525i
Quote:
Originally Posted by rdl View Post
Fuel pump relay changed locations over the years.
These are what come in WDS



See also:
- How to test a BMW battery & alternator (1) & the most often recommended diagnostic procedure to test for overnight parasitic battery drain (1) & one user's attempt to locate, describe, and photograph all fuses and relays in the BMW E39 with a picture of every fuse & relay (1) & how to choose a good aftermarket battery (1) and a simple battery replacement DIY (1) & Cn90's explanation of where to get alternator rebuild parts (1) & how to troubleshoot a bad FSU final stage unit (1) and how to build a test jig for your FSR final stage resistor (1) & how to repair solder cracks in your blower motor resistor (1) & how to replace your HVAC blower motor control (1) (E46) & what FSU is the right one to buy based on user experiences (1)
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See also: E39 Bestlinks & How to easily find what you need
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