No power, won't unlock

[ItalianTuneUp]

Strange thing happened yesterday: the key remote failed to unlock the car. I had to use the detachable real key from the fob to gain entry.

Then the next surprise: after putting the fob in the ignition, it would not turn!

Comand will not turn on, no radio etc.

I took car for a long drive only 3 days earlier and it's a new decent battery. It's possible the battery has run flat but I'm a bit surprised.

Three days ago, I remember that the remote was also having difficulties opening the car...I had to press the unlock button multiple times before the car unlocked.

Any ideas?

Edit: I'm wondering if rain/damp has somehow got into the electrics. We've had a lot of rain and wind recently, so perhaps it just needs to dry out?

I tried two fobs and I checked the IR signal was being emitted, with a smartphone camera (good tip).

 

[Harrythedog]

Does sound like the battery

 

[ItalianTuneUp]

Thanks Harry, so just try jump leads to get it started/provide power to get ignition working?

 

[Harrythedog]

I wouldn't know about that. Just for reference the same happened to me a while back and the battery (from MB) was less than 6 months old and I went one morning and had the same systems as you. They tested the battery, a full days job!, confirmed it was US and replaced it. If you can I'd try and put it on charge as a first port of call

 

[ItalianTuneUp]

Thanks for the advice. I don't have a charger so will have to try the jump start method for now. It was a silver varta battery, and it's only about 3 months old, so I'm puzzled.

 

[IanA2]

It was a silver varta battery, and it's only about 3 months old, so I'm puzzled.

That should still be good and under warranty.

 

[ItalianTuneUp]

That should still be good and under warranty.

Yes, it should be fine.

After connecting jump leads, it started straight away, so it was a flat battery.

After driving about 30 mins up motorway, the speedo started moving rapidly up and down...when I was driving at a steady speed, then the car slowed down, and I was thinking "so this is limp mode?" And expecting to have to call the RAC.

The dash controls and lights were flashing and I was beginning to fear the worst.

After considering options, I decided to continue and see if I could blast the gremlins out, suspecting moisture from all the rain had got into the electronics, with the additional electrical problem of the battery having run flat.

I pulled off the hard shoulder and it seemed to drive fine, and no more funny business, so hope things ok.

One thing I did notice though was that when I put the right indicator on, the relay ticking seemed twice as fast as normal, and dash message told me to check indicator bulb. Upon parking up, I noticed that the mirror-mounted indicator was indeed not flashing and was showing that it contained moisture.

I'm wondering if the mirror indicator has shorted with all the rain, and has caused a short circuit that has drained the battery due to high drain? Plausible or not?

 

[E270 Owner]

Alternator / Battery Control Module












.

 

[ItalianTuneUp]

I hope it's not the alternator

The thing is that I drove it little in the last couple of weeks, so I'm hoping it's just lack of use that allowed battery to go flat, due to the usual devices draining it whilst parked up. But perhaps you're right. Will check it again later.

 

[ItalianTuneUp]

Well today the car unlocked, started and drove fine. No issues except the fault with the mirror indicator, which I'll have to take a look at, but I suspect it's just rain that's got in there.

It could still mean there is an issue with the alternator, but only time will tell.

 

[mbnerd]

Yes, it should be fine.

After connecting jump leads, it started straight away, so it was a flat battery.

After driving about 30 mins up motorway, the speedo started moving rapidly up and down...when I was driving at a steady speed, then the car slowed down, and I was thinking "so this is limp mode?" And expecting to have to call the RAC.

The dash controls and lights were flashing and I was beginning to fear the worst.

After considering options, I decided to continue and see if I could blast the gremlins out, suspecting moisture from all the rain had got into the electronics, with the additional electrical problem of the battery having run flat.

I pulled off the hard shoulder and it seemed to drive fine, and no more funny business, so hope things ok.

One thing I did notice though was that when I put the right indicator on, the relay ticking seemed twice as fast as normal, and dash message told me to check indicator bulb. Upon parking up, I noticed that the mirror-mounted indicator was indeed not flashing and was showing that it contained moisture.

I'm wondering if the mirror indicator has shorted with all the rain, and has caused a short circuit that has drained the battery due to high drain? Plausible or not?

Had the same crazy erratic speedo, rev counter and dash stuff with my SL500 for ages. Even got messages about SRS not working and "Drive to Workshop" which was a bit scary but, everything would go back to normal quite quickly so I just ignored it.

Problem was water getting in through the air conditioning intake due a blocked drain hole and basically flooding the passenger side of the car. Was in the workshop for nearly 2 weeks while they dried everything out and fixed all the wiring that had got damaged under the seat. They have modified the drain hole now to stop it blocking up again and admit that it's a design fault. When I collected my car another SL500 had just gone in with the same problem

 

[ItalianTuneUp]

Yes, that sounds exactly like what happened to my car too. Quite worrying when it happens out of the blue when driving along, eh?

I will see if I can check for a similar issue. The air conditioning intake is just under the bonnet near to the bottom of the passenger side windscreen isn't it? And where is the drain hole located? What was blocking the drain hole, leaves?

 

[ItalianTuneUp]

Well, well, after another spin out in it today, zero problems surfaced.

The indicator works normally, and the indicator relay ticks at the usual speed, so I assume that the moisture issue with the indicator has gone away. :bannana:

Does anyone know whether moisture inside the mirror-mounted indicator could cause a short / high drain that would sap juice from the battery?

If not, then I assume that a combination of little use over a period of time, plus sustained heavy wind and rain has caused this issue.

 

[ItalianTuneUp]

mbnerd, where is the blocked drain hole that you mentioned? I will check my car's drain hole to check that it is not blocked.

 

[mbnerd]

Looking at the car from the front; under air conditioning filter located below the grill in the bonnet at top right, next to the battery. Below this is a kind of water trap funnel which tapers down to the drain hole.

 

[ItalianTuneUp]

My battery is in the boot, but I know roughly where you are referring to, so I can maybe take a look. Hopefully that drain can be seen by looking down from the bonnet area.

 

[mbnerd]

Koolvin mentioned the same drain block problem in the Check your A and B class for wet carpets thread.

 

[ItalianTuneUp]

Yes, I have been looking at that thread, thanks

 

[prestige lease]

My car doesn't start either and alarm keeps going off which drains ths battery. Someone told me its your wiring under the passenger side footwell which gets wet and croded.

Please let me know how you got on and some advice please.

 

[ItalianTuneUp]

My car doesn't start either and alarm keeps going off which drains ths battery. Someone told me its your wiring under the passenger side footwell which gets wet and croded.

Please let me know how you got on and some advice please.

The first question is, has the car had little use recently?

The symptoms described earlier have more or less gone, but not completely.

The mirror indicator was erratic for quite a few months but seems to have fixed itself now. I had SRS warnings, ESP warnings flash up randomly, even EPC messages. These spurious messages have all come and gone.

The only message of concern remaining is a red battery charge message, which seems to appear in known circumstances: when cc is off and the foot is taken off the accelerator, letting the car slow down naturally. Weird.

I think these cars have so many computers that the chance of some random error message appearing is quite high, and wind and rain seems to bring all these errors out of the woodwork.