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Smart key - line of sight?

5K views 33 replies 14 participants last post by  inamoto 
#1 ·
I've done a search and not seen this exact question, so here goes.
Had the 2006 SLK350 a month. I've seen posts that say the long whip antenna plays a role in reception of the key signal so that the door can be locked/unlocked from a distance. I have the original long antenna but I have to point the key directly at the door handle to unlock / lock the car. If I am out of the line of sight for the handle, no response, even if I am three feet behind the car.

What is normal operation with the key? Could there be a problem with the antenna?
 
#2 ·
#3 ·
From your owner's manual:

Hold the SmartKey in
close proximity towards the antenna
base when locking or unlocking the
vehicle.
 
#4 ·
The key uses RF for locking/unlocking, which isn't line of sight - the signal is picked up by the antenna, and passes to the amp/splitter. It is not unknown for corrosion to occur in the antenna base which can greatly reduce the range of the key. Again, it is not unknown for the co-ax connections to work loose from the splitter. Are your radio/phone functioning correctly?

If you have 'remote roof operation', this operates by IR and is therefore 'line of sight'. You must point the end of the key at the receiver in the door handle. The system is a waste of time - as Jeff said, get a SmartTop - THE best mod for an SLK :)
 
#5 ·
Sounds like as if your key is only sending IR signal ..can you operate the roof with key pointed to the door handle
 
#6 · (Edited)
First, buy a $4 CR2025 key fob battery and replace (Panasonic or Energizer) and then recheck. No use doing a lot of effort for a weak battery.

Gordon

PS Just checked: With new key fob battery I can lock and unlock my car in the garage from my desk in the den. Thats more than 60 feet, passes through 4 walls, a walk in freezer in kitchen, 2 motorcycles and a Weber BBQ before the antenna.

I am still suggesting fob batteries. For roof opening I need to be close but I am unlocking and locking my car from anywhere in my house no matter which way I am facing and no matter which way the car or antenae are positioned. There are 2 batteries in my fob and if they are not positioned correctly or one is weak or dead, performance is degraded
 
#7 ·
First, buy a $4 CR2025 key fob battery and replace (Panasonic or Energizer) and then recheck. No use doing a lot of effort for a weak battery.

Gordon
I've had my car a bit over a year and on Monday, I got a message to replace the battery in the key I always use (wife has the other, but she seldom uses it). Went to WalMart yesterday and picked up a pack of two 'CR 2025' batteries for less than $5. Went ahead and replaced the battery in both keys and I noticed this morning that the 'range' to unlock the car did seem to be a bit better.
 
#14 ·
Wow. Thanks for all those replies. Love this forum. Right after I got the car, I replaced the batteries in both keys, so they are strong. The remote open/close of the roof works fine if I point the key at the door handle and hold the button down during the full cycle. This is cool because you can better observe the admiring glances of passers-by. :)

GBD069, that's a great range you are getting, and I see that you have an 05, so I should be able to get something similar. Now that I know it's supposed to be RF, I'm going to follow-up on Wolly's comment about the antenna, and remove and clean the base, then do some testing.

By the way, in defense of Gbarringer100, that jaw trick can work. I first saw it when I left my car parked in a marina parking lot and I was down at the boat. I tried the key from my location and... nothing. I was going to have to walk back into range. My son, who had worked at the now defunct Circuit City said "put the key up by your jaw and open your mouth" and try it. I did and the lights flashed and the car locked. Scouts honor. I've done it since in similar situations.. sometimes it works, other times not so much. Now for you doubters - "If I use my wife's jaw, I get twice the range!"

Thanks for the key input. I'll report back after I try some things and I'll look at SmartTop.
 
#15 ·
...
GBD069, that's a great range you are getting, and I see that you have an 05, so I should be able to get something similar. Now that I know it's supposed to be RF, I'm going to follow-up on Wolly's comment about the antenna, and remove and clean the base, then do some testing...
I should have asked if you are having the same issue with both keys. In any case I swapped out the dead key fob batteries in an S series with some no-name batteries and they never worked right. You mentioned you have changed the batteries so maybe you can mention why you changed them? Same problem? If so then then the antenna solution is likely.
 
#16 ·
When I first got the car, the range on the key seemed pretty short and one key was a little quirky, so the first thing I did was pop into Best Buy and get a pair of new batts. Now both keys work the same but need to be line of sight with the door handles, and I think need to be within 10 to 15 feet of the car.. I'm out of town now but next Monday, I'm going to start checking the antenna....
 
#17 ·
Been away for awhile, but to update this post, I did pull the antenna and check for corrosion (there was none), but it was not on very tight. I cleaned it and tightened it hand tight, and checked for loose connections in the wiring. Nothing there either. Still only works from about 5 to 10 feet line of sight from the sensor on the door handle. I think Smart Top is in my future!
 
#18 ·
You missed the smarttop sale while you were gone!
 
#20 ·
Blown fuse to the Antenna amp - does the radio pick up stations as per normal ..?

Cheers
Sean
 
#22 ·
Sounds like the key only transmits in IR. RF part may not be be working. Was the remote key fob ever exposed to high humidity?

Unscrew the whip antenna and check the integrity of the antenna base, and the integrity of the central "pin" located within the threaded base of the whip antenna itself.
 
#24 ·
Just a teaching grandma to suck eggs post ....

these little button batteries are extremely easy to short out. Just holding them normally between your fingers can do it. So you think you have put in a new fully charged battery when in fact you haven't.

Either don some rubber gloves or use a plastic pair of tweezers to install.

Grandma is spitting out the shells as we speak!
 
#25 ·
Just a teaching grandma to suck eggs post ....

these little button batteries are extremely easy to short out. Just holding them normally between your fingers can do it. So you think you have put in a new fully charged battery when in fact you haven't.

Either don some rubber gloves or use a plastic pair of tweezers to install.

Grandma is spitting out the shells as we speak!
You are welcome. (No one ever listens to me)
 
#28 ·
Sean wins the prize

I'm happy to report a resolution / solution to this problem. It's been a while since Sean's reply to this thread but I'm happy to report that he seems to have nailed it. I was busy and don't drive the car much, so I just lived with this key remote being line of sight and limited to about 6 - 8 feet, BUT recently I had the car in for service and I mentioned the issue to the mechanic.


After he checked it out, he said the fuse to the "radio portion of remote locking" was MISSING. He put a new fuse in and now I can lock/unlock the car from halfway across my house with the car in the garage.
 
#29 ·
Great! get a SmartTOP and do it from 300 feet away!
 
#32 ·
Hi Dr!

MB wants the money so they probably won't program it unless you have an 'in' with them. specifically they cannot guarantee the key not theirs will work at all. so the answer is NO! :D

Oh and don't forget to post an intro! and check out the smarttop!

Your 1st thread should be your introduction so we can welcome you properly so post an introduction in the ‘New members introduce yourself here’ section, if you haven’t already. New Members Introduce Yourself Here - Mercedes Benz SLK Forum

Welcome to SLKWorld.com: The #1 Mercedes-Benz SLK Forum from Valrico, Florida!

owner's and maintenance manuals great R171 info:

later year owner's/maintenance/comand manuals, top right in the link below:
Bill's Den: Documents

Lube those seals:
http://www.slkworld.com/226839-post1.html

your brochure:
http://www.slkworld.com/general-discussion/167265-mercedes-brochure-archive.html#post1511249

mods you should do:
smarttop

http://www.slkworld.com/general-discussion/121481-what-smarttop-all-members-keep-talking-about.html

clear or tinted side markers
shorty antenna
led license plate bulbs
led parking lights
carbon fiber on the C pillars http://www.slkworld.com/general-modifications-r171/50849-ive-taken-cf-plunge.html
oem windscreen or lighted/etched windscreen
Post your vin in the Vehicle Datacard Request section to get a free datacard (options on your car).

http://www.slkworld.com/vehicle-data-card/67706-free-how-get-free-datacard.html


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