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Just curious: What is the purpose of the three relays in the trunk battery box?

77K views 12 replies 6 participants last post by  bluebee  
#1 · (Edited)
Just curious what the purpose of these three relays in the trunk battery compartment is ...

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The realoem diagram didn't help much:
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I also looked in Realoem control units, modules, sensors, relays:

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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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#3 ·
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.
 
#4 · (Edited)
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?
The Unloader kills power to the electrical system when the car is in start position ( cranking )
- Unloader Relay ????
Unloader relays cut power to all but necessary electrical items when you are engaging the starter.
JimLev said:
I have 4 relays, 4th is fuel pump.
Does yours look like this?

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#8 · (Edited)

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#9 · (Edited)

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#11 ·
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
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 ·
#13 ·
This thread today covered the various locations for E39 fuel pump relays...
> E39 (1997 - 2003) > Fuel Pump relay in 03 525i
Fuel pump relay changed locations over the years.
These are what come in WDS
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