Battery Drain 'DOME' fuse

[mr2tourist]

Hey all.

So, I bought a new battery and checked the alternator is charging.
The battery was still lasting about a day so I did the 'parasitic drain' test and on pulling the 'DOME' fuse the needle (yes, my multimeter was used by Noah) dropped to almost nil.

I believe that I have a problem with the aftermarket 'adjustments' someone has made to my otherwise stock headunit that (I believe) is causing huge battery drain.

There's a 10 disc changer in the usual place but there appears to be some wiring around the footwell fusebox and some sort of box of tricks that I assume makes the changer talk to the stereo.

BUT: It all looks like it's been wired OK. So I am assuming it's just been wired up wrong.

Possible 12v constant instead of switched?

Problem is I have no idea where to start now!

[markstevieandmads]

Sometimes the alarm.is on that circuit too.

Next I'd disconnect each audio component until you narrow down the one causing the problem.
If disconnecting the lot still doesn't help then start looking at aftermarket alarms and I believe interior lights are on that circuit.

Just for your info, i have the same problem but narrowed down the problem to my Clifford alarm. The battery backup siren doesn't do battery backup anymore so this causes the drain.
I haven't got round to changing the siren as the car is locked in a garage with another car behind it. It doesn't get used for weeks on end so I just discon the battery when I'm not using it.

It will last about 3 days Max with a brand new battery fully charged without disconnecting.

[Nails]

My first mr2 had a drain and that was the alarm was furbarred. If the lights are on that circuit then your boot light could be staying on also.

[mr2tourist]

Hadn't thought of the alarm. The siren is in the engine bay. Would it just be a case of disconnecting the siren? Is that where the brains are?

How do I go about disconnecting parts of the audio system. Where are the amps and associated components powered from?

[Nails]

How I tested mine was just to lock it with the key and not arm the alarm. Battery was fine the next day so got a new alarm fitted. Not exactly scientific but it worked lol.

[mr2tourist]

Mm. Well locking the car without arming the alarm makes no difference. Could it be the aerial as this is stuck halfway, but the motor to retract / extend can be heard to run and stop when you turn the stereo on or off. Going to pull fuses in the footwell if I get time this weekend.

[Nails]

Have you checked the boot light is switching off? Stick your mobile in the boot while video recording.

[mr2tourist]

Ok. Checked the light in the boot, it's not that (Thanks Nails).
I pulled all the fuses in the footwell. Didn't make any difference.
And I started to remove the box of tricks that controls the electric windows when the alarm is armed.
I've lost the plot of what is on the 'DOME' circuit and don't know what to check next.

Forgot to say the 'box of tricks' is not anything to do with the cd changer as previously thought.

How do you disconnect the factory alarm? That's my next attempt.

[markstevieandmads]

The aftermarket alarm on mine doesn't make no difference to the drain if armed or disarmed but when actually downpowering the alarm it does.
So don't rule out the aftermarket alarm until u completely discon it.

[mr2tourist]

Still no idea where this battery drain is coming from...

[Torero]

Hi Mate,

I'm having a similar issue on my UK Rev 5 - well pretty much the same as you actually - but I realised that every time I've had an issue I've been doing something with the dome light (interior light in the roof) and twice after I've messed with the unit the new battery runs down.

So I decided to disconnect the unit completely and the moment I put the screwdriver into the fixing screw the doors locked without me touching anything so there must be a short somewhere.

Anyhows, I did this on Sunday night and the battery drained so I tried to arm the alarm and it just kept going off. However, when I COMPLETELY disconnected the battery the alarm sounder was still going off (apaprently there's a battery in the sounder). I can tell you it's located below the passenger side front light, just disconnect the lifting arm from under the car (unscrew the trays) or wheel off and remove arch liner and you can get to it. You may be able to trace some of the alarm circuitry and wiring from there as well.

Just a note, disconnecting the sounder does not disarm the alarm circuit.

Keep us all posted and I'll do the same.

John.

[mr2tourist]

Hey. Misery loves company. At least I'm not the only person having this problem! Thanks for your reply. My alarm siren is in the engine bay (Rev2) however I did know the siren on yours had battery backup.
I think it's possible that the battery backup on the siren can drain your battery so perhaps try diconnecting the siren?

I think the alarm 'detects' the doors are opened if the interior light comes on. At least that's how many alarms take their signal feed. Maybe that's why your door locked?

I'm not sure where to look next. I will, however, try and detect a short in the interior light. Is this fused off the drivers footwell fusebox? because if so it's not that. I was still getting the drain with all those fuses pulled.

[mr2tourist]

So it's not the alarm as with that disconnected there is still a huge draw.
It's not the amplifier behind the drivers 3/4 window.
It's not the CD changer power itself.

Still hunting... Open for ideas?

[Peter Gidden]

Still hunting... Open for ideas?

Try the alternator. Had a few caught me out over the years.

[mr2tourist]

Interesting. Hadn't thought of that. With it charging ok I assumed that it wouldn't be the problem. Is it easy to disconnect in situ?

[Peter Gidden]

Is it easy to disconnect in situ?

Disconnect battery.

From underneath, undo main alternator terminal and cover wire terminal with tape to insulate it from surrounding metalwork.

Umplug the 3 pin plug.

Reconnect battery.

[mr2tourist]

Guess I know what I'm trying tomorrow then...

[mr2tourist]

Not that then...
How many audio amplifiers are there?

I think they might be live all the time.
I found one behind the drivers seatbelt and disconnected it but if there's more than one then there'd still be a significant draw.

[Peter Gidden]

This is not a difficult job - an hour a the most.

You've pulled each fuse in the car?

[mr2tourist]

Yep