Car won't unlock

[dursleyman]

We have 2001 C200K Avantgarde that has suddenly developed a problem with unlocking. It only happens if the car has been left for a while, such as overnight. We obviously suspected the key fobs so the dealer replaced the batteries in both but the problem still persists.
Most mornings we can spend about 10 minutes walking round the car pressing the fobs like idiots until it finally unlocks. Very frustrating, not to mention embarrasing.
Any ideas please?

 

[OmniCognateNeutronRangler]

have you tried it against the driver side door? The fob has both an RF (radio) and an IR (Infrared) transmitter. If the RF one is dodgy, as it is on mine, you will need to open it using the IR. Point it at the little square at the left hand end of the drivers side door.

if that works then you'll need to get it looked at and it may not be cheap. Cost £600 last time (under warantee) and only fixed the problem for 6 months. Mine's in again this week or next, when they can get the parts, to have it fixed again.

 

[television]

As Neal says have you tried the IR locking.

Can you put up part of car number is it 203745.743, 742,245,242,042 or 045

Malcolm

 

[dursleyman]

Yes, we have tried the IR by holding the key fob close to the little square on the drivers door and it does not seem to make any difference.

The chassis number starts 2030452

 

[mioba]

could there not be a main battery problem of the car itself, if the battery is low on juice, surely the reciever will not be functioning as it should.

check your main battery,as you mention this occurs after car is left for a while.

 

[s999sws]

Hi there, this once happened to me, and it turned out that after an overnight stop the main car battery had reduced in voltage by only about 1-2 volts. This was enough to give remote opening problems. Get the car battery checked at a battery specialist.
regards
Stephen W-S

 

[television]

Yes,before i do a search, this is the time of the year when batteries fail fast

To test, engine off,headlights on should be 12.5 volt, 12volt min.

malcolm

 

[dursleyman]

Good suggestion ref the battery, When I finally got it unlocked the battery tested at 12.4v, with headlights on it was down to 11.9v.
The car still starts fine and then the voltage tests at 14.6v with the engine at tickover, and even with the lights on, so the alternator is obviously good. But then I had to try several times to lock it !!
I think its down to my local battery man tomorrow.

 

[television]

After a all night stop in the cold,the voltage could drop even more, your figures (voltage) were not too bad. If your battery man supplies good makes and you know him well.what are the chances of just swapping over and testing the remote.

malcolm

 

[dursleyman]

I like the idea of a swap test, but then we will have to drive the car there and its usually OK after being driven.
I may just go for a good quality new one to eliminate that from the possibilities. Hopefully it should not be too bad on price ( I guess about £60-£70) and a lot less than time in the dealers workshop.
Watch this space.

 

[s999sws]

Hi there
remember, when a battery is tested at a specialist, they put a full load, or almost full, on it. That's when any problems will show. You cannot just put a light or 2 on, it is not a proper test.
Stephen W-S

 

[television]

Hi there
remember, when a battery is tested at a specialist, they put a full load, or almost full, on it. That's when any problems will show. You cannot just put a light or 2 on, it is not a proper test.
Stephen W-S

Leaving all the lamps on you are drawing 14-16 amps, that will soon show on a poor battery,give it a few mins

Malcolm

 

[s999sws]

I have to disagree, the test used at the specialist draws about 300-400 amps for a few seconds, which is what a starter motor draws on a cold day.

 

[television]

I have to disagree, the test used at the specialist draws about 300-400 amps for a few seconds, which is what a starter motor draws on a cold day.

I do not mind if you disagree, the testing methods you are refering to went out of the window a few years back and do nothing to confirm the condition of the battery. The testers of today are small devices drawing a few amps over a time period.
the early ones that you descibe can in the case of a poor cell, temporily weld or fix. The effect being the following day mainy in a temperture change condition can leave the faulty cell high ressistant and US, you may get it to charge again with a voltage in excess of 20 volts, but its all a waste of time.

With our cars and modern electrics a difference of 1volt can be the stopping point for the car starting or not.
It is not the discharge rate, it is the amount of stored energy that counts, you see when the voltage falls off,on the battery the cranking amps go up,this can damage the starter. it is a complex subject where means of testing have changed to High Tech and not in brute force.
If you would like details of modern testers just ask.

malcolm

 

[dursleyman]

Couldn't do the battery swap so it will have to wait till the dealer has a look after Christmas but I just came across another post with similarities.
Have a look at post 14 on http://forums.mercedesclub.org.uk/showthread.php?t=22954&page=2
On a cross country journey last weekend I had an aftermarket sat-nav plugged in the cigar lighter and it cut out twice after running for about 1hr 45mins. We didn't use the radio much so cannot tell how that was.
I wonder if this is one of those SAM problems?

 

[television]

I think when Omni and you have got fixed up it will a good indication.

As in the other thread,the cigar lighter is a Key 1 switched item,that means direct from battery, the only way that this could turn off is by being switched off if the battery is low, or the running voltage has dropped below 11.75 volt. this can happen when one cell goes down as the residue voltage in the battery would drop to 10 volt, and running voltage of 11.75, certainly the locking would be effected.

Re the SAM, they rarely fail on their own account, in this case it would be the rear sam in the boot.

I still think this is a battery problem.

malcolm

 

[Iain the gadget]

Try these people.


www.tayna.co.uk;)

 

[ralphphilip]

my r reg has a key fob it will not open the doors or the boot i have changed the batteries and still does not work i can slide the key out open the doors but the alarm goes off so my will not start can any body help can i disarm so i can use it i need my car so i can take my out and about as she is disabled help would be app please

 

[dursleyman]

The dealer has now replaced what they call the "EIS switch" which apparently is part of the ignition and the car now seems OK. It locks and unlocks fine.
Cost of the part was over £180 +vat and labour.

 

[philfricker]

We have 2001 C200K Avantgarde that has suddenly developed a problem with unlocking. It only happens if the car has been left for a while, such as overnight. We obviously suspected the key fobs so the dealer replaced the batteries in both but the problem still persists.
Most mornings we can spend about 10 minutes walking round the car pressing the fobs like idiots until it finally unlocks. Very frustrating, not to mention embarrasing.
Any ideas please?

I've got exactly the same problem on a 2001 C200K Elegance. Key fob batteries have been renewed - worked OK from 30 yds away for one day then same again. RAC man checked the main battery yesterday and said it's OK. I also have a ESP warning message coming on now. Engine starting sounds fractionally more sluggish recently but still starts well once I get the car open. Could it be that the main battery is down a bit? How did dursleyman eventually solve it? Would really appreciate suggestions.
Was a new EIS switch the answer as shown in #19 above?