Mercedes-Benz Forum banner

Infrared keyless entry 95 sl500

26K views 10 replies 9 participants last post by  adrianmariannegrei 
#1 ·
It seems that my keyless entry is not working. I tried new batteries with no luck. What is the next logical step in this troubleshooting procedure? thanks for the help.
 
#5 ·
only if the car is flashing green and red, but locks are not operating...

that doesnt sound like it is the case here...



Test the remote itself to make sure it is still operational, hold the button for 3-5 seconds, make sure the tip flashes in red.

next, try to resync the key, lock, unlock the driver door with the key blade, put the key in the ingnition, turn to position 2, then off again, then cycle the key blade one more time in the door, while the green light of the door is still flashing green, aim the remote and push the lock switch. the flashing will pause if the car recieves a signal..

at this point, the key must be resynced, and you should be able to lock and unlock normally with the remote.

if the flashing stops (as mentioned above) but the car still does not recognize the key, you either have the wrong remote, or a bad module.
 
#6 ·
Keito, the electronic internals of key-fob do become damaged or defective over time. High chance that solder joints have become dry, or fatigue fractures developed around a component.
Question - is the keyfob creating an infra-red signal?
Even the visible light 'flash' seen after 2/3 seconds does not always mean an infra-red signal is going out.
Quick way to test this - use any digital camera (or camera-phone). Hold fob pointing toward your phone / camera. Press activation button, watch camera for 'flash' from module that naked eye cannot see. If no 'flash' (which is more like pulses, than a flash) then internals are defective and need re-soldering etc.
Try with any tv or stereo remote to see camera spot what naked eye cannot see.
There is a post of about two years back with photos, where a fob was opened and internals / battery posts re-soldered.

Good luck and regards,
Ali D-C.
 
#7 ·
3ali,

the key fob internals consist of surface mount components with a slim to non chance of delaminating under regular to extreme conditions...

also, all components in the key fob are solid state, except for the switch itself.

as far as the infrared beam, it is visible if you look at it in a dark room, so no need for the camera.

furthermore, the PCB, by design, makes it very hard to fail in a fashion that allows the test red LED to be excited, (notice the name "test LED", infrared not to be emmited...

basically the key for circuity is so simple, that you may get all or none in 99.999% of the cases...
 
#8 ·
Hi,

R129 SL500 129.67 - Imported from Japan. 1995.

I lost my key with remote. Everything was working perfect: locking/unlocking, green and red light was flashing.

When I lost the key, car was open, so i don't have any problems with alarm. I was using normal key without remote.

Few days ago i ordered new key with remonte in local Mercedes dealer.
Yesterday I received Key and employee Mercedes tried to pair key with the car.

After several attempts they said that the problem is in the car. They check something with the Star Diagnosis but they can't said what's wrong and i must leave them car for all day.

I don't think that the infrared system is down.
The key number is 140 760 14 06.
The red light in the key is working.
 
#9 ·
Do only certain locks lock/unlock?
Do the flashing lights flash with the IR? If so, how?
Does pointing the IR to a different sensor on the car change anything?
Does the door lock/unlock button inside the car do anything?
Does the physical key work the locks in the door? In the trunk? All the locks?

These will help you determine if your IR is sending, if your sensors are receiving, if the processor is processing, if the actuators work, if the pump works, etc.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top