2004 CL500 Electrical Issue and possible ABC Fault?

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New Member
Jun 20, 2022
CL500 C215 2004
For a while now I’ve been having small issues with my cars electrics, the main interior Dome Light which contains Courtesy and Map lights, the control switches for the sunroof and one of the interior climate control sensors has been causing one or two issues including a power drain which discharges the battery totally if the car has been stood for a couple of days.

I keep the car on a trickle charger when I’m at home which helps a lot.

I took the car in to have the power drain checked and I was told it was the dome light. So I purchased a fully tested second hand replacement and had it fitted, however it made no difference and the power drain has persisted. A few weeks ago I tried another dome light but that too made no difference but when I put my light back in, the courtesy lights didn’t work on both the dome light and the doors and an issue with the sunroof appeared where the roof would only inch open unless it was reset. Then it would work fine for a while before starting to play up again.

And this has continued until last night where things seemed to go very strange indeed.

My car has keyless go but it only works off the drivers door sporadically, mostly on locking but very occasionally on unlocking but over the past week its stopped working again.

I was out in a heavy downpour last night and visited a friend. When I came out the car unlocked on the keyless go and all of the courtesy and door lights came on, much to my amazement. But then when I pulled up at home my headlights refused to switch off! I had to sit for a good ten minutes turning the headlight switch on and off as well as the ignition and eventually they turned off.

When I came to the car this morning I didn’t even try to switch the headlights on but I noticed that the courtesy lights no longer worked and then after arriving at work I was told that the back of the car had dropped on the nearside left by a couple of inches.

I replaced the nearside rear ABC damper last year so I’m not sure if that has failed or this is linked to the electrical issues too.

There are no warning lights on in the car, the ABC lifts and lowers as it should but again the rear nearside left of the car is still sitting lower than the rest.

Is the damper likely to be a separate issue or is all of this potentially linked to the electrical issues?

I have booked my car in with my local Mercedes specialist, but they are incredibly busy and can’t take the car until the 18th July.

I can’t help but think there is water getting in around the sunroof and into the void where the dome light electrics are?

Any tips or guidance would be greatly appreciated.

Many thanks

Kindest regards.
It's highly unlikely that the ABC problem is tied into all of the other crazy stuff going on.
As a point of interest, when things go haywire, try to open and close the doors very slowly to see if that changes the electrical issues. I had one Daimler/Chrysler that had broken wires in the flex joint between the door and body. After repairing the 9 broken wires, all was good.
The flex joint between the door and the car body is a known defect. I experienced similar problems with my CL500. Unfortunately (and v e r y "bean-couterish") MB decided not to use connectors for the door cable harness. In my car, several cables were broken. It was a tedious work since the rubber hose is fragile and prone to cracking when loosening from the car body.

I also had to remove the door inner lining in order to reach for the cables.

If fixing it yourself, be careful, since there is an AirBag in the lining. Disconnect the battery prior to any operation and wait at least 1 hour so that the capacitors in the SRS is discharged. Then arm yourself with a soldering iron, a bunch of shrink tubings of different sizes and patience.

If at any time the SRS-chain is broken while the car ignition is in pos 1 and battery is connected, the SRS will set an error flag which has to be cleared using a diagnostic tool.

According to MB, the ABC-system oil was never to be changed which is pure BS. It should and must be replaced as the oil rots. When new, it is green and transparent but the aging process makes it go grayish and smelly. Also the filter in the top of the ABC oil container needs to be replaced. The ABC-oil pump is a coaxial type with two circuits. One for the ABC and the other for the steering servo. If the pump fails, metal particles will find their way out in the system. Not good.

There is a test called "Rodeo" that rocks the car during which the system is put to the test. Performing this will make the system set error flags if it detects any malfunctioning component.

Many electrical problems are in reality mechanical. Corroded connectors with water ingress is the cause of most of them. One typical example is the rear license plate illumination.
Go down on your knees and look. The lamps can be water filled as there is no way for any water to escape once it has gotten inside the lamps. This is also a known problem. Also the boot lid mach locking mechanism can be destroyed by water, something that most drivers never notice as they use the keyless functionality and never checks the lock.

(Water leaks in from a cracked 3rd brake light or a bad gasket. It can be fixed by lifting it out and by applying non-agressive clear silicone.)

If you suspect water ingress via the sun-roof gasket, check the dome light module connectors.

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