Parasitic Drain Fuse #48? Final Stage Resistor??

[McBegby]

Hi all, I’m suffering dead battery issues if my car is stood for a while.
I’ve let the car go to sleep mode & tested all the fuses for draw with a multimeter on 200m setting.

The only fuses showing a reading with their respective draw are:

#48 - 02.1 (heater a/c & heated spray nozzles?)
#54 - 00.1 (transmission control module [TCM]?)
#14 - 00.5 (multifunction control module 1 & servotronic?)
#79 - 00.3 (air suspension?)

I’m going to focus on the biggest draw for now. Is this likely to be the Final Stage Resistor at fault? Is there a test to check it? Or is it a case of installing a new one and just hoping?

It’s a 2003 3.0d UK spec if that helps?

Many thanks

[RocketyMan]

F48 (fuse 48) that goes to the A/C control module

The draw for this is NORMAL. Whenever you open the door, unlock the car...etc. This modules "wakes up" and you hear a little motor spin around. This unit will EVENTUALLY go to sleep after circa 15 mins..?

One test you can do for this is to sit in the car for approx 15 mins and see if you can hear the little module turn off. If you've noticed, that's why there's ALWAYS dust on the left side of those slats. The little fan is usually always circulating air when the module is not asleep.

[McBegby]

Originally Posted by RocketyMan

F48 (fuse 48) that goes to the A/C control module

The draw for this is NORMAL. Whenever you open the door, unlock the car...etc. This modules "wakes up" and you hear a little motor spin around. This unit will EVENTUALLY go to sleep after circa 15 mins..?

One test you can do for this is to sit in the car for approx 15 mins and see if you can hear the little module turn off. If you've noticed, that's why there's ALWAYS dust on the left side of those slats. The little fan is usually always circulating air when the module is not asleep.

Thanks RocketyMan - that was going to be my next point to check for a wiring diagram of what goes on with that circuit so that’s really helped

I did the 16min car to sleep step before testing. I think I’ll do it again and put my ear to the unit to see if I can hear the little fan. I was too busy grunting & moaning at the angle I had to lie in to test the fuses in the glove box at the time so all I got (& had time for) when I did it was to get the basic readings.

I’ve pulled the fuse out in the meantime to save the battery for now. Just need to figure out what’s making it stay on if it’s that

[RocketyMan]

Originally Posted by McBegby

Thanks RocketyMan - that was going to be my next point to check for a wiring diagram of what goes on with that circuit so that’s really helped

I did the 16min car to sleep step before testing. I think I’ll do it again and put my ear to the unit to see if I can hear the little fan. I was too busy grunting & moaning at the angle I had to lie in to test the fuses in the glove box at the time so all I got (& had time for) when I did it was to get the basic readings.

I’ve pulled the fuse out in the meantime to save the battery for now. Just need to figure out what’s making it stay on if it’s that

Do you have an amp clamp? I know it might be kinda hard, but you can take out the A/C control module and put an amp clamp around the battery supply to determine how much current it's actually pulling. It shouldn't be that much. I would expect it to be in the mA range...

[McBegby]

Originally Posted by RocketyMan

Do you have an amp clamp? I know it might be kinda hard, but you can take out the A/C control module and put an amp clamp around the battery supply to determine how much current it's actually pulling. It shouldn't be that much. I would expect it to be in the mA range...

Unfortunately no amp clamp. I think the project for the weekend is to

Put fuse #48 back in
Let car go to sleep mode
Listen for the hvac unit fan
Maybe pull out the HVAC unit - I believe it will just pry out?
Then see if the fan inside is doing anything
If it is, start unplugging stuff to see if it stops - maybe starting with the FSR/FSU?, then Aux Fan, a/c bits & bobs.

it’s literally consuming all of my thoughts at the moment.... electrics are my Kryptonite

Everything works so I’m not getting the usual things I’ve seen from other reports - blown fuses / ac not working / irregular/intermittent fan speed - none of that is happening.

[RocketyMan]

Originally Posted by McBegby

Unfortunately no amp clamp. I think the project for the weekend is to

Put fuse #48 back in
Let car go to sleep mode
Listen for the hvac unit fan
Maybe pull out the HVAC unit - I believe it will just pry out?
Then see if the fan inside is doing anything
If it is, start unplugging stuff to see if it stops - maybe starting with the FSR/FSU?, then Aux Fan, a/c bits & bobs.

it’s literally consuming all of my thoughts at the moment.... electrics are my Kryptonite

Everything works so I’m not getting the usual things I’ve seen from other reports - blown fuses / ac not working / irregular/intermittent fan speed - none of that is happening.

Awesome! Sounds like a good plan.

Yes, you can take out the A/C control module. Use a PLASTIC pry to carefully get it out. You will see the little fan in there spinning when it is active. Another way to see when you car is/is-not asleep is the master window switch. If you turn on the child-window lock, it will illuminate green. When the car goes to sleep, this green light will go out.

[McBegby]

So...... I reinstalled fuse #48, took the x5 for a good spin. Parked up back home, put the car into sleep mode, got distracted, went back to it about 2 hours later, listened for the fan in the HVAC unit (not the easiest to get yer ear-lug to the HVAC with the gear stick trying to poke your jaw/neck/face..... neighbours thinking I’m having an intimate moment with the interior of the X5 or stroking my face against it like a cat!!!!).

I managed to hear the little fan in the HVAC whirring away like a gud ‘un still.

Time to start unplugging stuff this weekend. Weather is pants today, better weather tomorrow, no brainer to tackle it tomorrow.

[Clavurion]

Originally Posted by McBegby

So...... I reinstalled fuse #48, took the x5 for a good spin. Parked up back home, put the car into sleep mode, got distracted, went back to it about 2 hours later, listened for the fan in the HVAC unit (not the easiest to get yer ear-lug to the HVAC with the gear stick trying to poke your jaw/neck/face..... neighbours thinking I’m having an intimate moment with the interior of the X5 or stroking my face against it like a cat!!!!).

I managed to hear the little fan in the HVAC whirring away like a gud ‘un still.

Time to start unplugging stuff this weekend. Weather is pants today, better weather tomorrow, no brainer to tackle it tomorrow.

So you left the door open and vehicle was still on sleep mode when you checked the fan? (The tell tales like gear selector lights were off.)

[RocketyMan]

Originally Posted by McBegby

So...... I reinstalled fuse #48, took the x5 for a good spin. Parked up back home, put the car into sleep mode, got distracted, went back to it about 2 hours later, listened for the fan in the HVAC unit (not the easiest to get yer ear-lug to the HVAC with the gear stick trying to poke your jaw/neck/face..... neighbours thinking I’m having an intimate moment with the interior of the X5 or stroking my face against it like a cat!!!!).

I managed to hear the little fan in the HVAC whirring away like a gud ‘un still.

Time to start unplugging stuff this weekend. Weather is pants today, better weather tomorrow, no brainer to tackle it tomorrow.

LOL! That was funny reading that!

So good! You were able to hear the HVAC module and the little fan spin. Next, were you able to confirm after 15 mins or so the fan stops spinning and the current draw on that fuse goes to a negligible level?

Originally Posted by Clavurion

So you left the door open and vehicle was still on sleep mode when you checked the fan? (The tell tales like gear selector lights were off.)

I forgot about the gear select being a good indicator if the car is asleep or not. For us manual guys, the master window switch has the child lock light on that indicates when it is asleep or not.

[McBegby]

So... update.
Car asleep - gearstick light off & all that jazz.
Pulled HVAC unit out with nonmarring plastic pry tool. HVAC fan was spinning.
Unplugged final stage resistor. HVAC fan stopped spinning.
Checked fuse #48 with multimeter, it was no longer pulling a draw.
Happy days, or so I thought......
I then plugged the FSR back in and the HVAC fan didn’t activate.
I took the car out of sleep mode HVAC fan started spinning and then put back into sleep mode by waiting >16min. HVAC fan stopping spinning.
Checked fuse #48 again, no draw.
So by unplugging the FSR and plugging it back in, it looks like it’s sorted itself/reset itself.
Next test I’ll take X5 out for a long spin tomorrow and see if the problem returns after a drive. I’m expecting it probably will.
If so I’ll order a new FSR - hopefully that seems to be the issue.