Need a little help. The last time my S500 was in the shop to repair the soft locking hydraulics, it came back with a new problem, The key fob would not unlock the doors nor the trunk from a distance. I have to place the infrared part of the fob about an inch from the driver's side doors infrared receiver to unlock. Most of the time it will work but at other times I have to manually unlock then lock it back in order for the fob to work. (tired of the alarm when I open the door.) :-) I took it back to the mechanic and was told they checked all the possible problems and suggested I purchase a new key fob. that might be the answer except both of my key fobs will not work when they were working just fine before going to the shop. Any suggestions will be appreciated...NOTE: I did not check the fuses as I'm taking the mechanic at his word that they checked everything.

 

moved to W220 forum...

 

While it doesn't appear to be too likely that this is the problem, my first suggestion is that the fob battery might be getting weak. Use the tiny serrated slide to release the metal key inside the fob.Then insert the hook end of the key into the slot on the end of the fob and pry out the battery tray. Look carefully at the battery before removing it from the tray so you can insert the new battery the same way. Get a proper replacement battery, insert it into the tray, put the tray back in and put the key back in.

Let us know what happens.

 

WallyP…Sorry, I should have mentioned that I did change the batteries using ones purchased from Amazon several years ago, so I suppose those batteries could be too old. I’ll purchase fresh cells and update. If others have suggestions please let me know.
thanks!

 

Be aware that a significant percentage of the name-brand button cells on Amazon and eBay are counterfeit Chinese knock-offs.

 

90 percent likely it's the battery. Lasts only like 2 years, CR 2025

 

Hello all, well purchased 2025 Energizer Ultimate Lithium buttons, replaced the old ones, which checked out as good and in the green, and it did not solve my issue. Would the problem be with the antenna receiver? As I stated before, the shop replaced and repaired the hydraulic locking mechanism and the remote issue came about immediately as I tried to pick up the car. I took it back and they can’t seem to run down the problem. They suggested It’s probably the actual remote and to take it to the dealer. I don’t think that would be the problem with both remotes. What say you…

 

A similar problem on my 2003 S500 turned out to be either a failed antenna amp or a faulty connection between the antenna amp and the rear window antenna.

The connections between the rear window antennas and the amp are spring fingers on the amp touching connector pads on the window. I purchased a used amp from my local pull-a-part very cheaply, pulled the rear part of the headliner down and installed the replacement amp. Since I cleaned all of the electrical connectors, spring fingers and window pads during the installation and added Stabilant connection improver, I can't say for certain that the old amp was actually bad, but the problem is fixed.

 

I seem to go through key fob batteries like candy.