Can anyone help with this problem.

[Matt45]

Been having some electrical problems which are baffling me and the MB dealership. This is all warranty so should be OK but need some help in diagnosing the problem.

2 weeks ago on monday went to the car to go to work and the car would not open. Eventually opened the car with the metal key and started the engine. 2 faults showed: 'light sensor, drive to workshop' and 'convenience functions temp unavailable'. Went to MB dealer and they took the car there and then and ran a full diagnostic check but NO FAULT FOUND. They changed the rear battery just in case it was that which was causing the fault.

Following sunday the car would not open and had to open with key again. Only one fault: 'convenience functions temp unavailable' indicating rear battery not fully charged. Drove 150 mile round trip to Midlands GTG - car fine. Booked it back in for another check as suspected there was a proper drain on the rear battery.

Car went in last thur/fri and they checked for a drain but again NO FAULT FOUND. I put the battery on a low charge [3.7 amps] for fri evening to give the battery some more juice but it never reached full cahrge [?]. Went away for the weekend in wifes car and left the SL in our garage but not on charge.

Yesterday when we got home went to check the car but it would not open. Opened it with metal key, again, and started the car. 2 faults showed: 'light sensor, drive to workshop' and 'convenience functions temp unavailable'. Went into MB this morning and told them the whole story, again. They said it can't be the battery and they don't think it's the lighting sensor but could be 3 other things including the PFP pump??

Car seems OK if run every day but if left for more than 48 hours it's flat and I can't open with central locking fob. All faults clear within about 2 or 3 miles of driving. This is driving us mad as it has been fine for 10 months and I've not had anything done or changed to cause an obvious problem and we obviously don't want this to go on. I know the SL electrics can be sensitive, but surely the battery should not discharge in 48 hours after a run or a charge.

Does anyone have any experience of this or any ideas of what could be the problem. It's booked back in to MB next monday for the week to try and fix but I'm concerned. Any help gratefully received. thanks, Matt

[BlackC55]

You have a current drain and it needs to be tested properly. It is not a thing that can be fixed quickly either.

[Matt45]

Thanks, but they said not even though I'm with you on this one.

Any sugestions where the drain is commonly from or is it just too complicated to guess.

[BlackC55]

Too complicated to guess really. I suspect it is an int drain which is the worst. The most likely culprits are SAM modules, PSE pumps, and the command unit.

[glojo]

Too complicated to guess really. I suspect it is an int drain which is the worst. The most likely culprits are SAM modules, PSE pumps, and the command unit.
Totally agree and been there, got the t-shirt.

What are the usual journeys\mileage you do with your vehicle and how often is the car used?

Regards
John

[sheff1972]

I have had a few SL like this , it would be worth checking the boot area for water leaks , this then gets into the pse pump and causes a drain and in total failure mode blows the fuse , I would edge my bets at the pse pump.

[Matt45]

Totally agree and been there, got the t-shirt.

What are the usual journeys\mileage you do with your vehicle and how often is the car used?

Regards
John
I do only about 6 miles to work mon-fri and use the car for longer journeys at weekends and holidays. Been fine for months but now....

[Matt45]

I have had a few SL like this , it would be worth checking the boot area for water leaks , this then gets into the pse pump and causes a drain and in total failure mode blows the fuse , I would edge my bets at the pse pump.
Funny you should say this. The car has been modified with the new seals and up until a week or so ago has been dry in the boot. We went to France a month ago and the car was left out where it got damp but not wet on the carpet floor but only a bit. Seems odd it should suddenly leak and I have checked the drains etc and see no reason for water to ingress now but it did. The timing of the dampness and the fault are suspiciously similar so maybe you're right. Thanks for the help, I hope they manage to fix it cos I'm getting pee'd off with it always being in the garage. Matt

[glojo]

I do only about 6 miles to work mon-fri and use the car for longer journeys at weekends and holidays. Been fine for months but now....
Those short journeys will crucify the battery but it will take time to show up, plus the week-end mileage will effect this.

My money is on a slight leakage, but the 6 mile journeys are taking out more than is going in. Do you have any comfort features that operate before the engine starts? That is also going to take out a few buckets of volts.

I accept you might not like this, but modern cars, especially our vehicles, are loaded with electrical gadgets and they need that alternator to replenish everything we extract, otherwise over the weeks\months, the battery will gradually deteriorate :o :o

I am speaking from bitter experience. ;)

Regards
John

[Matt45]

John, Thanks for that. Over the last 10 months I only occasionally [4 or 5 times] get a low battery warning in the form of 'conveniance functions temp unavailable'. I have a battery charger that I can use to top it up but I accept that the gel battery gets used hard. It has, however, never drained flat until these last three times - and the battery is brand new so I'm starting with a fresh cell. I am generally sympathetic to the battery by not using features I don't need to. The only things that come on at start are folding mirrors, my phone and auto lights but I never leave anything on more than a few seconds as I always drive off straight away and get power back into the battery soonest. I have few extra features on the car so I'm concerned. It should work after only 48 hours of being parked even if the SL is complicated. I have never had any alternator or battery warnings. Matt

[bigtruth]

This issue is very similar to what I am currently having with my CLS. I guess I need to visit the workshop.

[jaymanek]

I had a drain on a W203.. after battery drained a little it caused locks to lock/unlock constantly.. we changed the whole system.. all locks, rear SAM, various relays etc...

it ended up being the ignition switch drawing a large current as it was not shutting down once the car was locked...

[glojo]

John, Thanks for that. Over the last 10 months I only occasionally [4 or 5 times] get a low battery warning in the form of 'conveniance functions temp unavailable'. Hi Matt,
Our E-class has been back to the workshops on about three occassions in four years for the exact same symptoms you are talking about.

The dealership have always been extremely helpful. They have kept the car connected for days on end to try to locate the seepage. They have replaced variosu expensive bits, but after three or four months the battery would be flat.

It happens so rarely, and always appears to happen without warning, but what I eventually did, was to record every single journey the car did and then picked a figure out of my hat regarding distances to re-charge the battery.

I estimated\guessed the car would need to travel a minimum of ten miles without switching the engine off to top up the battery, anything after that would start putting a charge into it.

Most of our journeys were actually six miles or even less, so in my non technical opinion, our driving habits were taking out more than was being put in. The problem, or plus side being that we would occassionally go on a longer run which would charge up the battery.

Our car has numerous electronic options that when we add things up I guess there will be a very minimal, very slight power usage, and I now have the main battery connected to a trickle charger. Touching wood as I type, we no longer get these very annoying warnings about comfort options being switched off! :o :o :)

I am NOT saying our problem is the same as yours, but I am suggesting you try recording the distances you travel in the car and record the mileages between engine stop. (A big three litre engine needs a fair degree of energy to start)

Regards
John

[Matt45]

I had a drain on a W203.. after battery drained a little it caused locks to lock/unlock constantly.. we changed the whole system.. all locks, rear SAM, various relays etc...

it ended up being the ignition switch drawing a large current as it was not shutting down once the car was locked...
I'm interested in this aspect because: when I came back from the garage on friday I drove the car into my dark garage, the lights came on as they were set to auto. I turned off the engine and the lights stayed on, not just for 15 seconds that they are set to but for about 4 or 5 minutes when I finally locked the car and they went out. Now I was sure they should go out, ie. I can park the car in the dark and remove the key and shut the door and not lock it, but on this occasion they stayed on. Am I right - should they stay on or go off? The dealer says they 'should stay on' until I lock the car - this doesn't seem right.

[Matt45]

Hi Matt,

I am NOT saying our problem is the same as yours, but I am suggesting you try recording the distances you travel in the car and record the mileages between engine stop. (A big three litre engine needs a fair degree of energy to start)


John, many thanks and I agree in principle but my SL has 2 batteries; the front acid battery for starting and a gell battery for the vehicle. It always starts adream and so I must be putting enough back into that battery. It's the rear vehicle battery that seems to discharge. Matt

[glojo]

John, many thanks and I agree in principle but my SL has 2 batteries; the front acid battery for starting and a gell battery for the vehicle. It always starts adream and so I must be putting enough back into that battery. It's the rear vehicle battery that seems to discharge. Matt:D Snap,
The E-class has tgwo and it has ALWAYS been the rear battery that has let us down

regards
John

[Matt45]

:D Snap,
The E-class has tgwo and it has ALWAYS been the rear battery that has let us down

regards
John
Didn't realise. I'm convinced it's something to do with the lighting circuit as per the 'light sensor' warning but the lights do go off so it could be a drain through the circuit or a connection with the ignition switch to the auto lights. I'm adiment that they shall sort it out as I only have 2 months left on the warranty and I don't feel inclined to pay them to fix a fault at a later date. My wife is cross that such a prestige car should have so many problems. I feel a new car coming on. Thanks for your help. Matt

[Diesel Benz]

:D Snap,
The E-class has tgwo and it has ALWAYS been the rear battery that has let us down

regards
John

The difference here is that the front battery on the E-class does not start the car like it does on the SL. If the rear goes flat, the E won't start but the SL does. The front battery on the E is only a backup for the SBC brakes (does not exist on the face lift with normal brakes).

[Diesel Benz]

I'm interested in this aspect because: when I came back from the garage on friday I drove the car into my dark garage, the lights came on as they were set to auto. I turned off the engine and the lights stayed on, not just for 15 seconds that they are set to but for about 4 or 5 minutes when I finally locked the car and they went out. Now I was sure they should go out, ie. I can park the car in the dark and remove the key and shut the door and not lock it, but on this occasion they stayed on. Am I right - should they stay on or go off? The dealer says they 'should stay on' until I lock the car - this doesn't seem right.

I'd have to cover my light sensor to be able to test this at my garage but according the manual, lights should never stay on more than 60 seconds. If you switch off the engine and don't open the doors, lights would stay on and wait you to leave the car, but not more than 60 seconds.

I'm not able to interpret the manual if the delayed switch off time starts from closing doors or from doors locked, the manual states:
Setting night security illumination
(Exterior lamps delayed switch-off)
Use this function to set whether and for
how long you would like the exterior lamps
to illuminate during darkness after exiting
the vehicle and the doors closed.

If you have seen lights on for 2 minutes, it sounds to me like some sort of an issue with the appropriate SAM (water or something else) or some other control unit? :confused:

[jaymanek]

they do normally stay on for longer if the car is unlocked.. this is so you would be able to find your way away from the car in the dark... for example pulling up in a dark car park.. you walk off, get to a lit area and then lock the car and lights go off..

[Diesel Benz]

they do normally stay on for longer if the car is unlocked.. this is so you would be able to find your way away from the car in the dark... for example pulling up in a dark car park.. you walk off, get to a lit area and then lock the car and lights go off..

The manual says:
If you do not open a door after removing
the SmartKey from the starter switch, the
lamps will switch off automatically after
approximately 60 seconds.

But this is different from the scenario you mention so the manual may not conflict with what you say (and I take you talk from experience and the car behaves like you describe).

But do the lights then stay on forever if you don't lock the doors at all? Or is there another timer for this that the manual does not mention?

I guess the time as set from the cluster is just the minimum time then that lights stay on (like if set for 30 seconds, lights would stay on 30 seconds if doors were locked immediately but would switch off immediately when doors are locked if that happens 60 seconds after leaving the car?).

I've had this feature on several cars, I guess from W210 onwards but you can see that I've never really used it, I have it switched off.

[jaymanek]

no they will go off after a few minutes if left unlocked... im sure its programmable somewhere..

[l5foye]

I await with interest the cause of Matt's problems as I had the same ones. In my case, getting the gel or AGM battery charged at the dealers cured the problems even though dealers' machine said ' Replace battery' (?)

[Dieselman]

they do normally stay on for longer if the car is unlocked.. this is so you would be able to find your way away from the car in the dark... for example if drunk..

:eek:

[Matt45]

I await with interest the cause of Matt's problems as I had the same ones. In my case, getting the gel or AGM battery charged at the dealers cured the problems even though dealers' machine said ' Replace battery' (?)
After I got home last night I put the battery on charge, determined that there would be enough power to save the 'Light Sensor' warning for the garage to see it on monday. Got it to full charge in about 1.5 hours. No prblems this morning but then there wouldn't be as I'd not left it for more than 48 hours. I shall re-charge the battery tonight and compare the charging time to try and guess the state of the battery after one night and 2 drives to work and back.

On the issue of the auto lights for Jay and DB. Car worked as advertised last night as follows:
Pull into garage with lights on auto. Lights come on.
Turn off ignition. Headlights go off but fogs and side lights stay on to illuminate area.
Remove key. Same but interior lights come on too.
Open drivers door. Same.
Shut drivers door. Lights stayed on but switched off after pre-set 15 seconds [10 seconds for interior].
Locked car. No change.

MB dealer was wrong about them staying on forever. Did note that when opening the boot with car locked or not the lights come on then too and seem to stay on for a long time. Didn't find out how long as I wanted to preserve energy and locked the car to switch them off.

On my original thread, the lights stayed on past the 15 second pre-set and after about 4 minutes I had to lock the car to switch them off. That was my concern, associated with the 'Light Sensor' warning that has come up twice with a flat battery.

Hope this fills in some gaps. Matt

[Matt45]

OK, just got the car back from MB. They've had it all week and have run a test on every circuit in the car and, guess what, no fault found. They are convinced that the car is behaving perfectly but to be on the safe side they have replaced the new battery with yet another new battery [rear gel] and have said if I have any more problems with it being dead after being left over the weekend they will send a techie out to my house that morning so he can see the problem for himself. Can't say fairer than that really as they really are stumped by what's causing the problem. They weren't convinced of the reliability of the first new battery and think it could have just been bad luck that I got a duff one.
For those of you with similar problems, I'll keep you posted if things develope. Sorry to not have a concrete answer but then the gel batteries are a bit prone to problems so I understand. Matt