Parasitic battery drain, Mercedes GL420 CDI (2008)

[Chrislane]

Hi guys,
I seem cursed with battery drain, I had a Range Rover P38, and that always drained the battery overnight, it was intermittent, but always caught me out on a cold morning, the battery completely drained!

My Merc GL420 CDI is also internment & will hold a full charge for about a week, but when I go to start it, all the interior lights, are bright, the radio comes on but when I turn the key, the engine just clicks and doesn't turn over, the odd time it will start if I try turning the key again. I have a small Halo battery pack that will turn over the engine and start the car. I have a connected volt meter and shows 14.2 volt when the engine is running and immediately when you turn the engine off it drops down to 12.1 volt and quickly drops down to about 10 volts.

I've tried turning all the interior lights off and the radio/media system off when I park up, but makes no difference.

I've had a new battery fitted and a new, small accessory battery ready to fit(I don't know what this small battery runs, and what effect it has on the car)
I've read many things about parasitic drains and it seems its a matter of systematic search of all fuses and relays, which is like finding a needle in a haystack. The problem tends to be worse in cold weather.

Had anyone had this problem, and can you narrow down my search.

I've contacted an auto electrician who says he can't give me a price, as it could take 5 minutes or 5 days to identify the drain

Thanks for taking the time to read this long post, and any suggestions will be great fully recieved.

Have a GREAT Christmas everybody and a very Happy New year.

Regards
Chris V Lane

 

[Lenny63]

Do you have command in this beast? Cd changer or tv tuner? Im assuming if so its.fibre optic?.
I had a drain on my w219 cls and it was the old analogue tv tuner unit...and the sat nav unit...both were faulty and had been exposed to water ingress ...turns out the w211 and w219 have a seal in the teat bumper which allows moisture in..yhis was causing my drain.
May be worth looking at where the nab unit and rear sam is in the GL to see if you can see any water ( i have read GL and ML both have water ingress issues)
On another note ..
How are you find the gl420? Id love one

Regards

Lenny

 

[Petrol Pete]

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

Might give you a few pointers. Best of luck.

 

[Chrislane]

Do you have command in this beast? Cd changer or tv tuner? Im assuming if so its.fibre optic?.
I had a drain on my w219 cls and it was the old analogue tv tuner unit...and the sat nav unit...both were faulty and had been exposed to water ingress ...turns out the w211 and w219 have a seal in the teat bumper which allows moisture in..yhis was causing my drain.
May be worth looking at where the nab unit and rear sam is in the GL to see if you can see any water ( i have read GL and ML both have water ingress issues)
On another note ..
How are you find the gl420? Id love one

Regards

Lenny

Hi Lenny,
It had an aftermarket media/satnav when I bought it which was naf! I bought another and everything seems OK with that.
I LOVE my GL420, but alas its failing me badly , I took it in to sort out the drain, but....it hasn't moved since before Xmas, it's bang in the centre of their workshop and they can't get it out of park!
It seems the intelligent servo module has given up the ghost (Nowt intelligent about that!)
The auto electrician has been looking around for one and there are loads out there, but none to fit my car! Then if we find one, it will need coding to my car!
As soon as I get it back on the road, it's probably going on webuyanycar, one thing after another is failing on the bloody thing

If anyone knows of a reputable ISM repairer and coder please give me a shout
Thank you

 

[Lenny63]

Hi Lenny,
It had an aftermarket media/satnav when I bought it which was naf! I bought another and everything seems OK with that.
I LOVE my GL420, but alas its failing me badly , I took it in to sort out the drain, but....it hasn't moved since before Xmas, it's bang in the centre of their workshop and they can't get it out of park!
It seems the intelligent servo module has given up the ghost (Nowt intelligent about that!)
The auto electrician has been looking around for one and there are loads out there, but none to fit my car! Then if we find one, it will need coding to my car!
As soon as I get it back on the road, it's probably going on webuyanycar, one thing after another is failing on the bloody thing

If anyone knows of a reputable ISM repairer and coder please give me a shout
Thank you

That's a shame mate - sounds like a rough ride. If its any consolation once you do the ISM itll be done and likely not fail again? Battery drains are common on Mercs of this era...as frustrating as it is !
But just check those modules listed above. If they still have a power source going to.them and are still on the OEM fibre optic loop then they could still be causing issues