Electrical System - gone crazy!

[din888]

Hello guys....

Early this morning I found the rear light of my CS '04 turned on (just the RHS). And the alarm somewhat disengaged/turned off. Thought I had left the lights on overnight and hence the battery had gone flat. But then the engine could easily start. BUT right after the engine is turned on, all electrical stuff went haywire - the rear wiper was moving randomly, the air-cond and PCM turned on and off every 5 seconds (at random too in no predictable fashion). The horn and signal lamps do not work at all. Checked the battery and it was kinda weak. Changed the battery but the situation persists. Any idea what sort of problem this is? Struck by lighting? Short circuit somewhere? Appreciate all thoughts and guidance on this. Many thanks....

[NelsonMX]

I have seen something similar when water has gotten into the interior...This is usually caused by a drain becoming disconnected at the sun roof. I notice you are in Malaysia.....any heavy rain lately?

Bob

[mudman2]

You don't say what year but i would change the battery right now, all sorts of funny things start to happen when battery is bad

[odix]

I agree with mudman2 -- for an '04 if you have not replaced the original battery suggest you do immediately -- and NelsonMX's water tip is also excellent.

Keep us posted!

[din888]

Thanks Bob. We get heavy rain all the time! Worst still, I only have "half a garage" at home, hence half of the car is exposed to sun and rain all day. Mechanic now will investigate the wiring at rear section of the car but the car boot can't be opened.

Does anyone know how to open the boot manually? Thanks!

[NelsonMX]

You may be able to open the glass part of the rear hatch. It is an electric release though so depending on your electrics problem it may not work....

There is a button under the wiper arm mount when you press it the glass should unlatch. Once inside there is a square plastic panel at the bottom of the door about 3 inches by 2 inches that you can pry off. Once it is off you can use a finger to move the lever to the right and the hatch will release.....

Hope this is of some help.....

Yes I have experienced some Malaysian rains!!!

Bob

[din888]

Many thanks Bob. As of today, the mechanic has stripped off "all" electrical stuff on the car ie external lights, internal lights etc in an attempt to trace where the short circuit could have taken place. Just wondering if short circuit is indeed the cause.....

[din888]

Oh yes, the mechanic somehow managed to open up the boot... Cheers Bob!

[wvicary]

Does your Cayenne have two batteries and if so which one did you replace?

[ManMN]

I have 2 batteries. Do I replace both? or are there such thing as "cranking" battery and "aux" battery?

[rizzo]

It's my understanding that the battery in the rear is for starting the engine. The one under the seat is for everything else...

I have 2 batteries. Do I replace both? or are there such thing as "cranking" battery and "aux" battery?

[Loren]

It's my understanding that the battery in the rear is for starting the engine. The one under the seat is for everything else...

I have 2 batteries. Do I replace both? or are there such thing as "cranking" battery and "aux" battery?

You are correct - in a two battery Cayenne the one in the rear is used for starting only and the one under the left front seat is for all other vehicle electrical.

[din888]

I only have one battery. Mechanic is still unable to rectify the problem. Unable to find the orginal battery hence mechanic has put on "temporarily" a locally-made DIN 100 battery. Do you think this is causing the problem to persist?

[NelsonMX]

Was the problem there before you changed the battery to the DIN 100?

I am vaguely familiar with the DIN spec but I seem to remember DIN 100 is approximately the same size as the original. It shouldn't cause the problem your having unless the new battery is no good or not properly charged.....

Keep us posted...

Bob

[din888]

Yes Bob, the problem was there before i changed the battery. In fact I changed the battery thinking that was the culprit (it's 4 yearls old....hence good idea to change).

The mechanic has now found a blocked sunroof water outlet. This could be the reason for short circuit but he has yet to open up the dashboard to take a closer look. Any tips/past experience on this so that we could zoom in straight into the source? I also realize there's a "damp" smell when aircond is turned on.... this could also be related to the short circuit. My guess > sunroof water outlet blocked -> water trapped somewhere near or at the aircond louvre/blower and eventually causing the short circuit?

[NelsonMX]

Usually the water ends up in the passenger side foot well, and the carpet is wet. There are wiring harnesses running in plastic raceways under the carpet on both the drivers and passengers side so I would look there to be sure. In most cases just drying out everything thoroughly is enough to resolve things......

Bob

[din888]

Many thanks for the guidance Bob. Appreciate it. Will prompt the mechanic. Cheers.

[din888]

Hello guys.... found the culprit (and I hope it's the only one). There's somekind of lighting module located at the back of the car that got wet (due to leaking sunroof hose). It says "7LO 959 930 D" on it. Need to replace this. Do you know what this thing really is? Price? Thanks for the help...

[din888]

Oops it's 7L0 959 933 D .... thanks.

[din888]

After changing the "rear module", the car was back to normal (ie wipers are no longer activated by themselves, air-cond works, signals work) EXCEPT for

i) the rear boot could not be opened and

ii) the remote/central locking has somewhat been reconfigured - to lock the doors and boot, I press the usual lock/unlock button. Pressing the usual lock/unlock button again does not unlock the car. To unlock, I now need to press the "rear boot" button. And even then only the doors are unlocked. The boot remains to be locked.

Today the mechanic changed the "lock module" at the front door - and now the locking and unlcoking of doors are back to normal.

BUT, the boot still cannot be opened.

Any idea where the problem is?