Ir Door sensor repair – Mercedes W203 C class.

I have a W203 Coupe that had dodgy central locking. The central locking operates in 2 ways on this Mercedes. Infrared on the drivers door handle and radio frequency through the antenna amplifier.

Its common for the antenna amplifiers to fail, and on the coupe W203, requires removal of the rear window to replace. Its also common for the IR receivers to be absolute rubbish and barely work.

When your in that situation, you are stuck with a car that has very intermittent central locking. Here is a cheap fix for the IR side at least.

First thing to do is remove the door lock. One Torx bolt through from the inside of the door and it comes off.

You will then have to snip the metal tabs to get the sensor removed:

Once removed, you will have to remove the silicon conformal coating. Its best to start in the opposite corner that I did, and try and pull it off in one piece. IF you do as I did, you will have to pick bits out with a sharp knife, without damaging the PCB.

Once I had it off, it was obvious that there where 2 dry solder joints on the sensor pins:

Re-solder the 2 pins with some nice LEADED solder (Lead free solder is the reason there are cold solder joints):

Once done, cover with some more conformal coating (or something equivalent):

Once dry, I used a bit of metallic epoxy to secure it in place:

I can now use the IR locking from afar without any issues, even in direct sunlight!

Happy days.

74 total views, 1 views today

Switchable Dashcam powerbank circuit

So I wanted my dashcams to run for 12+ hours whilst parked, and I did not want them running down the main car battery whilst doing so.

There are a few commercial solutions available. Namely the Cell link B, which is basically a UPS for your dashcams. You connect the dash cams to it, and it powers them whilst your ignition is off. When the ignition is on, it charges the pack, and also powers the cameras.


Problem is, that its £180, which is too much.

So, I built a relay solution that does the same things with Ravpower USB power banks.

Here is the diagram:


It looks complicated, but it isnt. All it does, is use 2 relays to switch the USB connection from the vehicle to the powerbank, when the ignition is turned off. Keep in mind you could use a DPDT relay to do the same thing, but with one relay instead of 2.

This is what the end device looks like :


The 2 USB feeds are at the top. The output is on the right, and the two wires on the bottom left go to switched 12v. (there is a 1 amp inline fuse in these).

Keep in mind some devices support “chargethrough”. They say they support charging a device, whilst itself is charged. I find this dangerous unless it bypasses the battery circuit inside, and as we cannot be 100% sure, this is much safer solution.

I get roughly 16 hours on a “20,000mah” ravpower battery pack. I also use quick charge 2.0 chargers to replenish the packs, as short journeys will not put much into them.

Time will tell how long the Memory cards in the cameras last too.


340 total views, no views today

Mercedes S65 AMG M275 Airbox repair

My S65 AMG has the right hand side airbox tab broken off.

As a result, the airbox isnt secured into the inlet of the turbo, no good!

I designed and 3d printed a replacement.

Here is the bit that is broken.


and here is what its meant to look like:


Now I was not about to pay £500 for a new airbox so I set about 3d printing a replacement.

Some time later, I had a template:


After some measuring and printing, I had something usable.

I trimmed some of the broken pieces from the airbox and then epoxied it into place. Annoyingly, it dried in a slightly odd angle, but it should be fine!

img_20160930_074340521 img_20160930_074345774


592 total views, no views today