Weird electrical problem W204

[markg14]

I own a 2007 C-Class W204, and I have recently experienced some weird electrical problems.
The first problem I noticed was when I switched on the wipers, using the rotary switch on the stalk.
The wipers struggled to move, and eventually did a very slow, erratic sweep.
I selected another setting (double speed) and the wipers remained stationary. The wipers seemed to have a mind of their own, and so I booked it into an independent dealer for diagnosis.
On the day the car was booked in, the wipers behaved perfectly normally, but I still went ahead with the booking for diagnosis.
After doing their diagnosis, the independent’s analysis (for which they charged £125) was that I needed an new wiper motor - cost £510 inc parts and labour.
The car is booked in for next week.
Quite separately, I reviewed my house CCTV last night, and was shocked to see my car offside sidelights flashing on and off at 3am in the morning. Both front and rear offside sidelights were the only lights which were flashing on and off, quite randomly. This lasted for about 20 minutes, before the lights eventually went out.
Now I beginning to wonder if I have a more serious electrical problem which is not just involving the wipers.

Has anyone else experienced similar electrical problems?

All opinions would be welcomed.

 

[M80]

1st check battery voltage,
then look for water ingress that might screw with the SAM.

 

[markg14]

Where is the SAM? Although the car is 15 years old, the battery is the original and has never failed to start the car (the car is an automatic). Do you think the independents diagnosis is accurate? I am doubtful, as the wipers have been behaving ok since.

 

[M80]

I'm struggling to understand why the wipers would run slowly, other than low battery / alternator voltage.

The weird o/night happening would indicate a confused SAM. Here I'm assuming it would be your indicators that should flash had the alarm been triggered.

It might be water that's got into the wiper motor, and now dried out some.

 

[markg14]

I switched the wipers on to the first position (rain sensor position) and the wipers normally do one sweep before parking. On this occasion they struggled to make 1 sweep before parking. I then tried to activate the wipers by selecting the ‘constant’ position, and also the ‘constant, double speed’ position, but the wipers remained parked. This erratic behaviour disappeared as quickly as it came, and the wipers are now behaving normally. I am wondering if the independent dealers assessment of a faulty wiper motor is being mislead by another, more serious, electrical problem.

 

[tpn]

If your battery is the original one, since 2007 I would not attempt anything else before replacing it. These cars are so sensitive to failing batteries.
Otherwise it could be water/dampness in the front sam, as suggested, or a problem with the CAN bus

 

[markg14]

Just been out in the car today, and the fault has returned! The dealer says the diagnostics show that there is a fault code that indicates the wiper motor is faulty. Is it possible that the diagnostics are incorrect?

 

[LostKiwi]

Do you have the codes?

I've never seen any codes for wipers (not saying they don't exist just I've never seen one)!

 

[Blobcat]

If the wiper is slow then I can see a motor or mechanism fault - lack of lube is a regular issue

 

[Rotorhead500]

Offside sidelights being on would also suggest parking function has activated, so as well as battery age/condition and possible water ingress to SAM, as suggested, could also be a dodgy earth leading to electrical gremlin behaviour.

 

[mioba]

Wiper motors are not connected to anything readable by diags.
A slow wiper indicated - tired motor, did you access the mechanise and give it a lube?
Merc original batteries are fab, I am on my second battery in my 2004 W220 and on my original in my W251.

 

[markg14]

Well it turns out that the mechanism was partially seized, and the wiper motor has frazzled trying to overcome the stiff mechanism. Wiper motor and mechanism replaced, now working fine.

N.B. This work was carried out pre-MOT. MOT has subsequently revealed serious rust in the rear subframe, both sides have holes the size of golf balls. Mercedes contacted, and after an inspection by the local dealer, have immediately agreed to replace the rear subframe under warranty. Not a bad response from MB for a 15-year-old vehicle, but still a bit shocked that the steel used in the manufacture could rust so badly.

 

[ajlsl600]

Well done on subframe deal as u say at 15 Yr I suspect its done as a safety matter. They must have bought a crxp load of China steel or from fiat