2002 W203 Wagon 88,000mi

Just found the range is suddenly and severely decreased on my key fobs (Both Fobs).

The fobs work perfectly on Inrared, but apparently NOT RF.

Interestingly, both fobs worked both by Infrared AND RF prior to my changing the batteries in both remotes, though I am not sure if I ever checked the RF after the new batteries went in.

New batteries (now, again) apparently not the cure, and I checked their voltage, and it's good. And the reds flash when any remote buttons are pressed indicating it is transmitting.

I have read a LOT of threads on this problem, but mostly on the W202 cars, and I suspect things are a tad different on the W203 Wagon like I have.

The general consensus on the W202 posts is that it's the cars RF amplifier, or the connections between the car antenna (Presumably on the driver's side rear cargo area window?).

I understand that Fuse 8 on the trunk SAM/Fuse Panel (left side of cargo compartment in the wagon) controls the RF Amp, and is good, and reads 12v on both sides of the fuse.

I'd more blame a Fob, but but since both don't work, I'd doubt both would fail at the same time.

The owner's manual says that just plugging the key fob into the ignition switch will re-synchronize the fob, and no additional re-programming procedure is mentioned.

Anyone faced and found the likely cause?

FM Radio workes fine, but AM seems very weak (but I never really ever tried it before) I understand the AM shares antenna w/ Fob RF receiver?).

IR Portion of remote works fine (when pointed at the little black square in the driver's door handle).

Anyone know where the Amp is located on the Wagon (I understand it is either on the rear glass or the C Pillar on the sedan/coupe)?

Any suggestions welcomed-
Bob

 

I'm guessing it's where the rest are installed, at the top of the rear hatch glass.
Under the trim.
Lately I have a problem, that sometimes the key doesn't work to lock and unlock the doors..

I have 2 keys. One original, one replacement.
Original takes 2 batteries, replacement only one.
Been picking up new cells at the dollar store, (probably part of the problem)
and I've noticed the following.
The antenna seems to ...the backing...ie double sided tape, or whatever is holding it to the glass, appears to be failing.
And as such, not making perfect contact. Don't really want to mess with it though. Removing it can be a disaster and only should be done in the event it's completely hosed, which happens when water comes in contact with it,
frequently from tinting the back window with it left in the up positions, and water running into the
amp. There are these little rubber conductive pieces which will break and stay stuck...
I have a few spares if anyone ever needs and sees this, as I had a few spare antennas and sold them on ebay,
from breaking my glass twice (antenna comes with the glass).
And 2nd, I've noticed that the battery in the new fob, need to be replaced like every month!
2 was better than one!
Now, not sure if the loose antenna creates a need for a stronger signal, and therefore a stronger battery,
or the batteries from the dollar store are perhaps crap. But new batts always seems to work.

 

I have photos of two kinds of antenna amplifiers, with the one looking like an aluminum box reportedly coming from a W203 Wagon, and the others (flat, long, black) being stuck to the back glass with no mention of which car it fits.

The wagons are so much more rare, trying to get information is tough.

Because the wagon uses antennas on BOTH sides of the vehicle (on the rearmost side glass), I thought perhaps the amp might be located elsewhere (the silver box has mounting tabs for screws vs the stick-on long plastic one).

Given how easy it is to break trim pieces, I didn't want to pry at, and maybe break something until I was fairly sure I was in he right location.

Long, black, thin type: https://www.screencast.com/t/37JTE1qrE2

Silver box type: https://www.screencast.com/t/Q9DYwP5e

I think the long thin one is the type under the headliner card?

Bob

Fobs: I have one older black remote that uses 2 batteries, and a newer chrome/black one that uses one battery as well. As long as the little red LED near the tip flashes, I think you are sending a good signal with a good battery. There are testers at auto parts stores that actually receive the fob signal and confirm it is sending a strong signal, BTW, if you have doubts.