View Single Post
Old 02-04-2013, 07:58 PM
bluebee's Avatar
bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
Just my luck - my battery & alt tested good at both O'Reillys and Autozone today ...
> E39 (1997 - 2003) > It's my turn again: Dead battery ... two days in a row ... (yeah, I know what to do)

Like everyone else, I had replaced my FSU somewhere earlier in this epic thread <=== EDIT: It looks like I first came here in post #138 on 3/26/2008
EDIT: Found the dates:
a) I had put in a new FSU in, oh, about three or four years ago (need to check) <=== here's the thread ... 2/2/2009
b) I had put in a new alternator & belt drive system a few years ago <=== here's the thread 7/26/2010
c) I had put in a new battery only a couple of years ago <=== here's the thread ... 9/19/2011
So now I'm gonna re-read this canonical thread backward, to try to figure out which fuse is the one for the FSU ...

I'll edit this post once I figure out which one it is.

EDIT: OK. I found it. It's Fuse 76. Ensconced deeply under the glovebox (not in the glovebox, where fuses F1 to F46 lie).
Doing my homework, I find these quotes scattered about the forum, which relate to unplugging the FSU fuses:

Originally Posted by pleiades View Post
That's a single, square socket housing for two large fuses, F75 & F76, unlike the individual socket arrangements shown in the attached photos. And yeah .... it's hard to get your hand up in there (be sure to disconnect the battery first), let alone finagle the fuses upward and out with your fingers. Be sure to put the right fuse back into the right slot, too. Easily interchangeable.....
BEHIND GLOVEBOX (look from underneath):
F75 = 50A, Auxiliary fan (some say it's red)
F76 = 40A, Heater blower (some say it's yellow) [cn90 says it should have 12V when HVAC is turned on]
Or, I can just unplug the FSU ...

Originally Posted by JimLev View Post
Pull the bottom plastic panel off that is under the glove box, pull it straight back toward the seat.
Then unhook the side supports for the glove box.
This is what your will see.

Originally Posted by rog5878 View Post
To access F75 and F76 ... close the glove box and behind the glove box is a plastic panel with a hole in it (the panel is directly behind the glove box) Pull it towards you. Takes a bit of a nudge.
Then there are all kinds of wires bound together and various connectors that if you pull out will probably incapacitate the car -- who knows. I had to contort myself to lay on my back and look up in the well on the passenger side.
Yes, the two large fuses -- 75 and 76 are in the middle of this mess, and yes, it is a tight fit (took forever to locate them with the little flash light; some say they are obvious but they weren't to me; of course, now I know exactly where to look). God knows how one gets them in. To get the fuses out, I had to nudge the first fuse on each side -- couple of sparks -- God knows what those shorts did -- and finally it came out -- the fan stopped.
Originally Posted by bluebee View Post
1. Car dies periodically (and blower has wierdities at the same time)
2. Unplug FSU ...
3. If intermittent battery death stops, then you've pinpointed the problem
4. Replace FSU
If it's not the FSU, then I'll need to go, one by one, down all 88 fuse slots (F1 to F114).
To measure the current drain from your battery you will need to connect your multi meter in series with the battery and NOT in parallel across the positive and negative terminals. This would be OK to do this if you are measuring voltage. To measure current disconnect the negative terminal (I use the neg but you can use either), set your millimeter to measure amps and connect the meter between the battery terminal and the disconnected cable. If you don't have an amp meter then use a 12V test light bulb. The bulb will have a very low glow due to the current drawl from your clock, computer, etc. If the trunk light is on you will want to pull the bulb or fuse. If it is brighter then a low glow then you have a short somewhere in your car. If you want to see what the difference between a low glow (low amp draw) and a high amp draw turn on your head lights. You can pull each fuse and see if there is a change at the amp meter or pull the fuse and insert the amp meter across the fuse terminals (need to reconnect the battery of course). Checking each fuse (by pulling or direct measurement) will tell most problems except if you have a worn wire short on the hot side (positive) of the fuse box which is very unlikely.
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

Last edited by bluebee; 02-04-2013 at 11:57 PM.
Reply With Quote