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

it depends on the type of DME you have, for example the further most left is probaly for the fuel pump

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.

JimLev said:

Unloader relay, rear window defogger relay, and central locking relay

Click to expand...

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 )

Click to expand...

- Unloader Relay ????

Unloader relays cut power to all but necessary electrical items when you are engaging the starter.

Click to expand...

JimLev said:

I have 4 relays, 4th is fuel pump.

Click to expand...

Does yours look like this?

Yup, that's mine.

bluebee said:

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?

Click to expand...

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.

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

According to this thread today, apparently the 'fuel pump relay' is K96:
- Where is "MY" fuel pump relay? Pic inside

edjack said:

According to Bentley, K96, the fuel pump relay, is the left-most one on that rack.

Click to expand...

So, in the next post, I'll google for the location of K96 to see what I can find.

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):

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

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

JimLev said:

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

Click to expand...

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

This thread today covered the various locations for E39 fuel pump relays...
> E39 (1997 - 2003) > Fuel Pump relay in 03 525i

rdl said:

Fuel pump relay changed locations over the years.
These are what come in WDS

Click to expand...

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)