Key fob related issue

[Moby2005]

The other day my battery went flat as I don’t drive it that often, the key fob unlocked the doors from a distance before I tried the engine and realised it was flat.

I got a jump start to the car and drove to my destination to realise it only works now if they key fob is touching the sensor on the driver side door handle .

I have also lost the radio stations as it cannot find any and will just continue to search .

Not sure what the solution is, I have tried checking the fuses and non are blown , they say if you place the key fob sensor under your mobile camera you can or should see the light transmitting . However both fobs only show the red dot light at the front of the key fob and the batteries are new, taking into consideration the fob was fine up until the battery went flat.

I have had the battery checked too and is certified in working order therefore can put the battery being flat to minimal use but did not think it would have a knock on effect to the key fob signal and radio stations.

I would appreciate any assistance .

 

[mioba]

I would be inclined to get the car battery on an overnight charge if possible.

Did you spark anything the battery when jumping.

Oh and welcome to the forum, do stick around!!!!

 

[Droverunner]

If you are trying to self diagnose you really need a voltmeter so you can see the actual battery voltage and as said above use a good slow conditioning charge overnight. A battery may start the car but still have voltage problems that affect the electronic modules.

Also you need a Mercedes specific code reader to see if any are logged to give a clue to any issues.

Sadly these days with electronics a simple jump start needs avoiding or great care.

 

[Blobcat]

The keys work on IR and RF, the IR is the short range to the door receiver and the RF is the long range to the antenna (normally in the rear glass).
If you lose long range on both keys at the same tim3 the antenna pre-amp is a likely candidate for failure.
If you drop your keys then there is a coil which can become detached which also stops the RF long range opening.
Jump starting can cause some voltage spikes which can also knacker the car electronics.

 

[alexanderfoti]

The keys work on IR and RF, the IR is the short range to the door receiver and the RF is the long range to the antenna (normally in the rear glass).
If you lose long range on both keys at the same tim3 the antenna pre-amp is a likely candidate for failure.
If you drop your keys then there is a coil which can become detached which also stops the RF long range opening.
Jump starting can cause some voltage spikes which can also knacker the car electronics.

+1 check the fuse for the antenna amplifier (maybe marked as radio) on the fuse chart. It is quite common for the amps to fail as well though

 

[Moby2005]

I would be inclined to get the car battery on an overnight charge if possible.

Did you spark anything the battery when jumping.

Oh and welcome to the forum, do stick around!!!!

Hello

Thank you for replying , no when I jump started it there was no sparks at any point, I had the battery tested and was told nothing wrong with it, I just don’t drive the car often enough .
To date I have no radio stations and the fuses are awkward to get to under the bonnet however those have been checked along side the driver door side and none are blown .

 

[Moby2005]

If you are trying to self diagnose you really need a voltmeter so you can see the actual battery voltage and as said above use a good slow conditioning charge overnight. A battery may start the car but still have voltage problems that affect the electronic modules.

Also you need a Mercedes specific code reader to see if any are logged to give a clue to any issues.

Sadly these days with electronics a simple jump start needs avoiding or great care.

Hi thank you for your response .
I had the battery checked out and I was advised it is holding charge did not need replacing.
It was odd to lose the radio signals and fob usage as the battery has gone flat before as I don’t drive the car often .

 

[joderest]

I note you say battery holding a charge, but what voltage is it at ?
anything under 12.5 volts ( might be corrected on that) is low, hence may affect systems. It may well be you need a new battery, i can leave our car un started for two weeks or more, and its all fine on start up, battery is quite new as well.

 

[Moby2005]

I note you say battery holding a charge, but what voltage is it at ?
anything under 12.5 volts ( might be corrected on that) is low, hence may affect systems. It may well be you need a new battery, i can leave our car un started for two weeks or more, and its all fine on start up, battery is quite new as well.

I have just located the back fuse box which I did not think i had , I replaced the fuse 7.5 and it blows straight away