Wednesday, June 11, 2014

Keyless entry replacement on the W124

My wireless entry failed recently due to the siren wiring short circuiting and thus I am no longer able to use my remote to unlock or lock the doors.

Not too much of a problem as I'd always wanted to replace the system as the range of the old one was quite limited.

I had bought a keyless entry system from Aliexpress since 2 years ago and had no good reason to install it until a week ago when it rained so heavily that it shorted my siren +12V wire to ground and rendered the old keyless entry system useless.

This was the system that was purchased and the instruction manual looks like this.

Honestly, even for an electrical engineer, the instructions were quite useless...

Then I found help,at Peachparts forums, where many classic Mercedes owners, contribute technically to helping other owners, in this thread.

Monday, June 2, 2014

Flickering headlamp aka dash bulb warning light

If your W124 is experiencing a dash bulb warning light that comes on and off, it may be a hint that your headlamp connectors is not as tight as it should be anymore.

If the cause is not an actual faulty bulb, it is likely a loose connector.

This connector is one of the causes of a flickering bulb warning on your dashboard.

W124 Euro Headlamp Connector
It is the connector that connects to the headlamp.

After 20 or more years, the connectors might be slightly deformed and may not latch as well onto the male pins. A simple solution will be to add a layer of material on the non-conducting pin as shown below. This will introduce some friction and tightness onto the way the plug connects and will also increase the contact of the conducting pins. The material used was a 5mm diameter heat shrink.

DIY increase contact and better latch for headlamp connector

If this had solved your issues with the dash warning indicator, do share with other W124 owners!

Thursday, March 13, 2014

Update #1 on Airflow potentiometer replacement project

Following my post about replacing the airflow potentiometer with a modern alternative, here are some updates

Parts are in.

Simulated input vs output testing.

Using a truck throttle position sensor to vary the input signal and created the output signal.

Using PWM to drive a RC circuit to achieve an analog signal to be seen by the ECU correctly.

The results are quite pleasing. Achieving less than 10ms of delay between the actual response of the output signal mirroring the input PWM.

Click to enlarge to see the 2 lines more clearly

The best way to reduce the haze is to drive

Every car is equipped with an intake air filter.

The engine draws in filtered air, combustion occurs, carbon dioxide and water comes out of the exhaust.

So technically speaking, the dust in the hazy air is trapped by your intake air filter.

Dirty hazy air goes in, carbon dioxide and water comes out.

The perfect environment air filtration device for the haze that we are experiencing now.

There's your lousy excuse to bring your W124,W201,W126,W140,R129s etc for a drive.

And if the missus asks, show her this page!

Share if you like this article

Monday, March 3, 2014

Marshall Protocol Explanation and Location

Bought a "Mobius" action camera and created a small video of my journey to the weekly Marshall Protocol meetup for Singapore W124 owners group in Facebook .

Video is best viewed using desktops/laptops to see the annotations.
Annotations will not appear in mobile devices viewing this video

For the W124 owners in Singapore unaware of what is Marshall Protocol, it is a weekly gathering of classic Mercedes Benz owners such as the W124,W201,W126,R129 etc.

Friday, February 28, 2014

Air Flow Potentiometer Alternative Replacement

I am starting a project to replace the ancient air flow potentiometer that is present in most KE-Jetronic  (CIS-E) driven engines such as the ones present in pre-1991 W124s, W201, W126 etc.

This potentiometer is one of the most critical component of the KE Jetronic air-fuel metering system and it cannot be repaired. Bosch is said to have stopped the production of this item and whatever remaining stock out in the world is getting scarce.

To replace it with another old unit salvaged from another vehicle would be like swapping time bombs.

Hence this project to R&D a suitable replacement.

Modern electronics will be used to provide the same output as the air flow potentiometer that measures the swing of the air flap, which tells the KE Jetronic ECU how much air is entering the throttle body.

Air Flow Potentiometer with worn out tracks

The 3 pins of the existing potentiometer is namely the ground(0 volts), voltage supply(+5 volts) and the output voltage ( between 0.5v to slighly below 5v ) to tell the KE control unit what is the air flow.

We hope to garner as much interest, to KE(CIS-E) driven car owners, as possible and also to find out more if there were other efforts from other groups of enthusiasts around the world that had embarked on the similar project and would like to know their experience encountered during the design of this replacement air flow measuring sensor.

I can be reached at

Thursday, January 23, 2014

Steering wheel lock and key ignition barrel

At times when the key ignition is turned off and key is no longer in the ignition barrel, if you accidentally rotated the steering wheel as you exit/enter the car, you might hear a click sound which means the steering wheel has been locked.. [ fat thighs ].

That will cause the steering lock and when you re-insert the key again, there will be a problem turning the key to position 1.

Most might use brute force to turn the key to position 1, but this will cause the ignition barrel/tumbler to fail in the long run.

To be able to turn the key smoothly to position 1, you will need to unhinge from the steering lock by wiggling the steering wheel towards the position it was accidentally rotated to.

eg, if it was rotated clockwise by a notch after engine was turned off, rotate a little bit clockwise and hold it at that position while you turn the key to position 1. That will unhinge the steering lock and the key will be able to be turned easily and once it is in position 1, the steering wheel will be freed from the lock position.

Doing this will prolong the key ignition barrel/tumbler lifespan and also prevent the unfortunate occurrence of breaking the key within the barrel.

Share if you find this information useful.

In the meantime, here's a good looking W124 for you to ogle at.

W124 300E