drummerdimitri

Lately, every time i try locking the car by pressing the button on the door handle, the car locks but then i hear a weird clicking sound with a light pulse from the hazard lights and the car unlocks by itself.

This happens most of the time but doesn't seem to happen with the regular key only the keyless entry card. It sometimes works normally but does this most of the time.

What could it be?

ibeforreal

Could possibly be your car battery. How old is the battery?

drummerdimitri

I actually replaced the car battery with a UPS battery and ultracapacitor hybrid.

The battery has plenty of juice and never had any other problems with the car since the modification.

cybertronicify

These Mercedes really do not like voltage fluctuations. To my knowledge, a Supercap will self discharge pretty quickly if not constantly topped off. If the voltage when cranking drops below 8v, computers starts to drop out and cause all sorts of problems. Try to revert back to the oem battery and see if the problem still occur.

ibeforreal

You can easily check the voltage of your battery by doing the following:

With the engine off and the window in the instrument cluster set to miles or kilometers, turn the engine switch to the second position (just before starting the car). Push the "R" (reset button) on the instrument cluster 3 times. You will get a "UB" on the cluster followed by your battery voltage.

Then, leaving that indication on the cluster, start the car, without doing anything else. Once the car is running the display will switch to the charging voltage. This way you can see how many volts your car is receiving.

tusabes

You can't use a UPS power supply battery and expect the cars electronics to work correctly

The voltage drop while starting can trigger the faults

drummerdimitri

Guys, there is nothing wrong with the batteries or the capacitors.

I realized that as soon as i get close enough to unlock the car by grabbing the handle, the car automatically unlocks itself without having to touch the door handle.

To lock the car, I now have to press the button and get away from the car ASAP otherwise it will keep trying to unlock it.

Can I reset the system or is there some other problem here?

cybertronicify

You have keyless go. There are sensors on the door handle that detects your hand and unlocks the car. Pushing the button will lock the car. My guess would be you have an overly reactive door handle sensor? And since these sensors are based on capacitance measurements, you may have interference from something else.

ibeforreal

Does it happen all the time, some of the time, at home, anywhere?

drummerdimitri

Most of the time and anywhere.

ibeforreal

Don't know what year your car is. Do you have the Keyless Go card along with the key fob or do you have just a single smart key. Depending on the year they are different.

I have keyless go but mine has a credit card type sensor attached to the key. If I take the card off of the key ring and say leave it in the house I can still unlock and lock the car with the key fob but the keyless go doesn't work. The car will still start with the key fob just as if the keyless go didn't exist.

drummerdimitri

I have the card type keyless go.

ibeforreal

Try the simple stuff first. Have you changed the batteries in your Keyless Go card?

drummerdimitri

They are brand new so nope.

jnash

you have a bad keyless Go door sensor and the handle needs replacing. Try standing at another door, lock it, and walk away. See then if it stays locked.
You may have more than one bad so try all four doors separately.

drummerdimitri

Problem seems to have gone away. If it ever comes back, I will just lock the car and move far away from it as quickly as possible to avoid unlocking again.