Hey Guys, I've been able to solve the remote-unlock-lock-from-a-distance problem....and guess what was the problem that not even the dealer could figure out.... it was just fuse#8- out. Incredible, huh? Just had to replace that fuse in the trunk and voila!!! Everything is back to normal. Gee, I should request to be a MB dealer here.

 

Good job!

 

Thanks for posting the answer... this will be helpful for others in the future. Was that fuse in the rear, front, or interior fuse box?

 

Rear box

 

Thanks for letting us know

 

What distance are we talking about?

 

are you referring to fixing the horrible range on the remote keys?

 

Not really, I was talking about the problem of locking/unlocking from a distance and not having to aim at the IR port at the driver's door to unlock/lock it. I spent weeks searching for answers.... but all I got was, bad antenna booster module, the tint at the rear glass,rear SAM... anyways.... after spending time.... I finally went to check the fuses and voila....fuse#8 was out... that was the whole problem to this nightmare. :-)

 

Hi there -
It has been a while since the last post on this, but I have the same problem in a 2001 C240. Found fuse #8 was blown, but when it keeps blowing all of the replacements.

Does anyone know what I can check to keep the fuse #8 from blowing?

Thanks!
WW

 

Yep.

I looked around at the other forums, found out that the alarm siren, which is located (in US cars) in the right front fender well behind the tire, leaks acid from it's built-in backup batteries over time which eventually shorts out the circuits in the PC board within the siren unit.

By simply unplugging the siren from the wiring harness you remove the short.

Evidently you don't need to have the siren connected for everything else on the car to work ... however you just won't have an audible siren in the car anymore, nor will you have a battery backup to the alarm unit (and remote operation?)

To get to the siren you need to get under the rear portion of the right front wheelwell, where it meets the undercarriage panels, remove a bunch of fasteners, and get to the unit. The videos I watched had you jack up the car and remove the wheel to get access, but I was able to drive my front wheels onto a ramp and do it from underneath.

I removed one 8mm bolt holding the corner of the under-engine pan, two 10mm nuts, and two pushpin plastic rivet fasteners ... from there I was able to bend down the bottom of the fender well enough to reach in and undo the three 8mm nuts that hold the siren mounting bracket to the car, swing around the unit so I could see the wire connector, and remove the connector (it has a squeeze latch on it but not hard at all to remove). I bagged the connector to keep the dust out, and put the panel back on with fasteners.

30 minutes start to finish having done this for the first time ... when I put the new (or fixed) siren back in it will take me half that time.

Sirens cost $150-200 new so it's not necessarily a no-brainer expense to replace one ... there is a blog out there that shows how to cut open the old unit and replace the two batteries inside it ... not trivial, but maybe a fun project if you are handy with small tools and a soldering iron. I found the batteries for sale around $15-20 each and you need two of them (COMP-18-3NMH, 120H3A3H, 3XV150H, BN-24B, MBH0060 3.6V 150mAh). I don't know that I would buy a used siren because the batteries will be almost as old as the ones on your car -- unless you like doing this annually

-- John