e39, 2000 model year battery drain. Fuel sending unit?

[ejj2000e39]

Hello,

My fuel sending unit is going bad.
It sometimes takes several minutes, 20-30, before it will get to the fuel tank level. Will this cause battery drain when the car is off?

Regarding battery drain:

Can anyone provide the most common causes for battery drain on an e39, 528, 2000?

In this instance it is not the temperature control module or trunk/CD player or stereo.

Thank you.

ejj

[ross1]

A failed auxiliary fan(control) is another common power draw when standing

[ejj2000e39]

A failed auxiliary fan(control) is another common power draw when standing

Thank you for the information!

[mattmar1]

and the FSU, the controller for the interior blower. check if the car goes to sleep. open the trunk, close the car doors, do not disturb the vehicle in any way by opening a door, using the key fob remote. wait 16 mins. does the trunk light go off? if so, your car went to sleep. unfurtunately you wont hear an audible snoring though, if the trunk light doesnt go off, its nut sleeping. dunno if its an auto trans or not, but if it is, you can ignore the previous and watch and see if the "P" shift indicator goes out.
and no, the fuel sending unit will not cause a battery drain.

[ViolinARC]

On both the 2000 and 2003, I caught the FSU failing and fans activating.When I was working on other things I kept hearing fan noises. Hang out around the car and if you hear the fans cycling on and off while the iggy is off without any user input...replace the FSU and see if that solves the issue.

[DennisG01]

As mentioned, no, the level sensor won't be the issue.

How old is the battery? Are you positive that something is draining the battery? What's the battery voltage (read it right at the battery) while the engine is running, a few minutes after being turned off and then a hour or two later?

If it's not a battery/charging issue, could he just pull the fuse (or relay?) for the FSU and see if that keeps the battery from dying overnight?

[JimLev]

No relay and the fuse is behind the glove box, PITA to get at unless you remove the box.
Measure the voltage like Dennis suggested, but then with the engine off, key on, turn on the headlights for 1-2 min and see if the battery voltage drops below 12 volts. If it does the battery isn't holding a charge.