Battery drain - Fuses 36 and 42

Grumple

Member
Hi All,

I've tried to get help for this by piggybacking on old posts, and have read through countless other threads to try and work out how to diagnose this issue myself - I just need some help interpreting what I've found please.

Battery reading 12.65v

Testing current between the negative terminal and lead with a multimeter it reads 2.64A

I knew fuse 36 was an issue, and removing that takes it down to 0.37A.

Problem solving what else could be causing the drain, I plugged fuse 36 back in and disconnected the following and noted the drop in current after each item was unplugged:

Driver's door leads unplugged = 2.55A (-0.09)
Passenger door leads unplugged = 2.38A (-0.17)
(Door leads total drop = 0.26)

Front interior bulb = 1.73A (-0.65)
Front interior 'spotlights' = 1.06A (-0.67)
Rear interior bulbs = 0.23A (-0.83)
Boot interior bulb = 0.23A (no change)
(Bulbs total drop = 2.15)

With all the bulbs out, plugging the door leads back in takes it up to 0.53A (+0.30)

Removing fuses (including those in the passenger footwell), these are the only ones that made any change to this:

Fuse 01 = 0.38A (-0.15)
Fuse 36 = 0.21A (-0.17)
Fuse 42 = 0.07 (-0.14)

Disconnecting the CCU took current from 0.53A (bulbs out, door leads and all fuses in) to 0.30A (-0.23).

It seems very similar to this issue, but the bulbs rather than the door controllers seem to make the biggest difference:
https://www.a2oc.net/community/inde...ain-in-4-days-how-to-trace.22992/#post-177598

Does this give any indication to what is causing the problem?

What can I test/try next to help narrow it down?

Thanks in advance!
 
Door leads being disconnected:
20230217_112659.jpg

CCU lead disconnected:
20230217_124224.jpg
 
Have you checked the boot light doesn't stay on, while the boot is closed and the car is locked? Parasitic drain can be a headache for sure, I've been dealing with a low-current one myself :/
 
Boot light definitely not staying on.

Battery doesn't seem to hold its power as long now. When this first started I could leave it with negative disconnected for a few weeks, it's now only lasting a week after a full charge (and I'm currently broken down waiting for a friend to come and jump start me...)
 
Boot light definitely not staying on.

Battery doesn't seem to hold its power as long now. When this first started I could leave it with negative disconnected for a few weeks, it's now only lasting a week after a full charge (and I'm currently broken down waiting for a friend to come and jump start me...)
Time to invest in one of those little jump start battery packs. - Andy
 
Boot light definitely not staying on.

Battery doesn't seem to hold its power as long now. When this first started I could leave it with negative disconnected for a few weeks, it's now only lasting a week after a full charge (and I'm currently broken down waiting for a friend to come and jump start me...)
Perhaps the battery is on it's way out as well?
I recommend removing it from the car for 4-5 days and to check the voltage every day with multimeter/unplugged charger. When I tried to deal with the parasitic drain, I took the battery out, to see how it actually holds voltage, and turned out it lost charge in a few days, went from 12.4 to 9.5v in 4 days.
I got a new battery, and meanwhile the odd drain is still there, it'd only cause issues after not driving for weeks, but I drive almost daily, so for now I rather sort out other issues.
 
Perhaps the battery is on it's way out as well?
I recommend removing it from the car for 4-5 days and to check the voltage every day with multimeter/unplugged charger. When I tried to deal with the parasitic drain, I took the battery out, to see how it actually holds voltage, and turned out it lost charge in a few days, went from 12.4 to 9.5v in 4 days.
I got a new battery, and meanwhile the odd drain is still there, it'd only cause issues after not driving for weeks, but I drive almost daily, so for now I rather sort out other issues.
Good idea to check the battery, but having gone through all the testing I know there's current being drawn from something.
 
If you push the switches for the door closing on all doors and the boot while observing the meter (bulbs in), does it fluctuate ?

And did you try it with Blubs in and CCU disconnected. My car came to me as a project (dead) and it was the CCU casing parasitic drain. TBH i didn't really isolate this properly, I just went on "best guess" as its was one of the early units that were prone to it.
 
If you push the switches for the door closing on all doors and the boot while observing the meter (bulbs in), does it fluctuate ?

And did you try it with Blubs in and CCU disconnected. My car came to me as a project (dead) and it was the CCU casing parasitic drain. TBH i didn't really isolate this properly, I just went on "best guess" as its was one of the early units that were prone to it.
Hi mate, do you mean the physical switches on each door that activate when you shut the doors?

I'll try with bulbs in and CCU disconnected.

Thanks for the input - gives me some things to try!
 
Disconnected the cigarette lighter and stereo completely today and neither made any difference...

Where are the door switches? I couldn't see any physical switch around the doors or boot...


After getting a jump start on Sunday and driving roughly 15 minutes home, I tested the battery voltage:
Running = 13.72
Switched off = 12.99

It was reading 12.77 (-0.22) today - 2 days after not starting and being disconnected. I'm confused how if that drive home charged it enough to hold charge for days, why hadn't the drive there? Is it possible the immobiliser had kicked in for some reason, rather than it being battery issue?

What to try next?!
 
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Does the car alarm function correctly? If the sounder has failed the alarm may be triggering but you hear no sound. If this happens frequently this will drain the battery.

When you pull fuses etc and reconnect the circuit and lock the car it takes time for all the systems to go to sleep. Quite often you will see the current draw decrease as the systems shut down over a period of time.
 
I'd really suggest to scan the ccu, it's: engine-46. I reckon you'll have a few codes stored there, that might give you a hint.
 
Hi All,

I've tried to get help for this by piggybacking on old posts, and have read through countless other threads to try and work out how to diagnose this issue myself - I just need some help interpreting what I've found please.

Battery reading 12.65v

Testing current between the negative terminal and lead with a multimeter it reads 2.64A

I knew fuse 36 was an issue, and removing that takes it down to 0.37A.

Problem solving what else could be causing the drain, I plugged fuse 36 back in and disconnected the following and noted the drop in current after each item was unplugged:

Driver's door leads unplugged = 2.55A (-0.09)
Passenger door leads unplugged = 2.38A (-0.17)
(Door leads total drop = 0.26)

Front interior bulb = 1.73A (-0.65)
Front interior 'spotlights' = 1.06A (-0.67)
Rear interior bulbs = 0.23A (-0.83)
Boot interior bulb = 0.23A (no change)

(Bulbs total drop = 2.15)

With all the bulbs out, plugging the door leads back in takes it up to 0.53A (+0.30)

Removing fuses (including those in the passenger footwell), these are the only ones that made any change to this:

Fuse 01 = 0.38A (-0.15)
Fuse 36 = 0.21A (-0.17)
Fuse 42 = 0.07 (-0.14)

Disconnecting the CCU took current from 0.53A (bulbs out, door leads and all fuses in) to 0.30A (-0.23).

It seems very similar to this issue, but the bulbs rather than the door controllers seem to make the biggest difference:
https://www.a2oc.net/community/inde...ain-in-4-days-how-to-trace.22992/#post-177598

Does this give any indication to what is causing the problem?

What can I test/try next to help narrow it down?

Thanks in advance!

You have provided data on the current when disconnecting various circuits (red text above), but you didn't see any reduction when checking the boot interior bulb, did you find out why this was? If it's a non-led bulb then you should see a similar reduction to the other circuits (assuming it's illuminating in the first case that is).
 
You have provided data on the current when disconnecting various circuits (red text above), but you didn't see any reduction when checking the boot interior bulb, did you find out why this was? If it's a non-led bulb then you should see a similar reduction to the other circuits (assuming it's illuminating in the first case that is).

Sorry for the delay, had no notifications for some reason.

The bulb is standard. I assumed no drop when taking it out just meant it wasn't affecting the current when everything is off (as you'd expect)?
 
I'd really suggest to scan the ccu, it's: engine-46. I reckon you'll have a few codes stored there, that might give you a hint.
Sorry for the delay - had no notifications.

I don't have a scanner at all, and when I've looked into it before I don't think I'd have a clue how to use one anyway!

Anyone in the Basingstoke / Fleet / Guildford / Reading area I could visit for a scan?
 
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