Display problems on hot days

[Mikep]

C180 - 2001 : Intermittent problems . Get the message "Visit Workshop Display Faulty" , the petrol guage doesn't work, the indicator lights on the display go on but don't flash and car is difficult to lock or unlock. Has happened 3 times now - after car has been left in car park on hot, sunny day. Take it home , leave overnight, no problems . Any ideas?

 

[ianf]

I have the exact same problem, except on a C200.

Any ideas, thoughts, pointers or suggestions very much appreciated - no matter how silly

Ian.

 

[colechelle]

the problems you both have is the rear sam unit, this is located n/s boot behine a panel, if you remove trim from near side boot its the big block with fuses in, couple hundred quid but at mo your lucky if the fault is clearing with restart, easy job to do, but fuel guage has to be coded in using star machine, if you dont get it done you will find it will fail completly and put rear tail lights and number plate light on, sorry guys but you will have to call 24hr or into dealers

 

[ianf]

Thank you very much for your swift reply. Not the news I was hoping for (Contact cleaner or a similar solution would have been nicer to hear!), but thanks for the heads-up.

Ian.

 

[PINBALL]

Sounds like soldering dry joints or fuse holders weak/corroded, but mostly a poor earth will give these symptoms, particularly when the temp rises.Hope it helps,
Keith.

 

[jberks]

Does sound like it may be little more than dry joints as Pinball says. As an alternative to the £200 option, unless you are handy with a soldering iron, it may be worth contacting some of the ECU repairers who may be able to offer a cheaper solution by fixing your own unit.

 

[D.C]

this could be water ingress on the rear sam!! they are prone to leaking in on the front of the boot on the nearside!!

 

[colechelle]

some good replys guys but trust me on this one, yes water ingress could be poss but sam unit to high seen it so many times now the unit was just never a long term unit, new one is a lot better, by all means if you handy with printed curcits etc have a go but i never once sorted one, it will fail big time and the first your know is when you come out in morning to find a dead car

 

[ianf]

The problem occurs without rain so I can't see it being water ingress. I've monitored the problem with intense detail and there appears to be a number of faults (stemming from a single problem or simulataneous failures I cannot know), here's a breakdown:

1. Petrol gauge intermittent - seems to be working okay at the moment, but it was acting up a lot a couple of weeks ago (mostly zero reading, but occasionally incorrect level reading), lately it's been perfectly fine.

2. Indicators intermittent (no jokes please!) - when the indicators don't work the rear-window demist light appears half-on (dimly on) and doesn't respond to presses - also the windowscreen wiper doesn't work on the first click (slowest setting) - but does work in the two successive settings. Hazard lights are also inoperative when this happens. I suspected earthing problems but all seems well on the earths I know about.

3. Overheating - The temperature gauge goes above the normal 'level' setting of 80degrees. I noticed this after I'd left it idling for a while and it overheated (120degrees and steam coming out!) - the front fans were not operating at that point... but the fans HAVE worked since (all fuses are happy and intact). I suspect this is an unrelated problem, but I have mentioned it as I have noticed it since my first post.

Forgive me for burdening this forum with excessive detail, but this has become a serious problem (the indicators rarely work any more) and I'm hoping the extra detail would help clarify the diagnosis.

Thanks for all the previous posts - I shall investigate based on your suggestions, but if you can help further then I would be truly thankful (and the other drivers in my area will stop swearing at my lack of indication!).

,

Ian.

PS I realise this differs from the first post in this thread, but I have since had time to analyse my problem in great depth.

 

[alancolvin]

On my C240 (W203) the rear SAM (signal acquisition and activation) module failed, due to a single burnt out small component, and it took the voltage control unit (built in to the alternator) with it. The symptoms were the failure of many electrical items, including wipers, turn indicators, fuel gauge, boot release etc.

My local BM dealership said it required a new rear SAM module and a new alternator.

Even with MB's 'car more than 3 years old' discounts (10% off parts and 20% off labour) the bill for this came to £850.

For me, this was the last straw in a continuing series of expensive component failures.

In my opinion, Mercedes reliability is now poor, MB parts and labour are extremely expensive, and residual values no longer strong. You still pay a premium price but now get average or below-average value.

Reluctantly, because I love the car's design, looks and drive experience, I shall sell the car and buy Japanese.

 

[ianf]

The symptoms were the failure of many electrical items, including wipers, turn indicators, fuel gauge, boot release etc.

If it's going to cost more than £600 I'll just buy a new car, however my failures are intermittent and not identical to your own - does everybody still agree that my problem sounds rear SAM related?

Ian.

 

[robbo]

I feel sorry for the poor bugger who has to pick up the pieces and repair their nice new car.

 

[ianf]

Yeah, I would too - so I'd mention it. As it goes I've solved part of the problem.

The fuse box under at the front of the car has a covering plate, I unscrewed that and uncovered a number of relay-boxes. When I pushed down on the big black one (descriptive powers are maxed-out here I'm afraid and I don't know their names) the electrical faults I had went away - so I whipped out all the relays, contact-cleaned their legs & and sockets and presto, the intermittent indicators and wind-screen wiper problem is now solved.

So can anybody shed light on why my petrol indicator works 100% fine now, but didn't a few weeks ago?

The overheating is undergoing further analysis (by myself), but I'm suspecting a faulty sender unit.

I hope my solution proves useful to somebody (at some point) - again, thanks to everybody who has taken the time to post suggestions thus far.

Ian.