Over time, it became apparent that the issue wasn’t the soft close.  All the electrics had stopped working on the tailgate.  This became obvious when the bulb out warning came on.  The number plate lights were not coming on, the wiper was not coming on and so on.   Since the 3rd brake light is a bit of an afterthought on these cars, it is not linked to the bulb out sensor, but it was also not working.

It was clear that the issue was my tailgate electrics.   As everything was not working, it was obvious the ground wire had broken in the harness.   The ground wire is the thickest and is the most likely to break.

I had a couple of options.  Repairing this wire, or replacing the harness.  I elected to replace the harness.   I figured that after 30+ years and almost 400,000km, I would be playing whack-a-mole with the rest of the wires if I tried to fix them.   The trim in this area is very brittle and taking it on and off wasn’t ideal.  Plus it would end up being more time consuming and expensive.

I purchased a new harness from Kurth in europe and waited for it to arrive.   This job was also an opportunity to fix a few other things that needed doing at the time.   Some of my trims around the rear aperture were broken and I found a much better set for sale.   My 3rd brake light housing was cracked, so I got a reproduction one from OctoClassic.   There is also a long plastic piece that goes on the bottom of the tailgate.  Mine was all cracked, but I was able to buy a complete spare tailgate.  That car had been white with a palomino interior.  I took a piece of broken trim and went to autolac who made me a spray can in the correct cream colour for my car.

I was going to try and do this job myself, but after almost a year of not getting to it, it was time to send the car to a professional.    I’m glad I did as the job took four hours for somebody with experience.  It would have taken me at least double, probably more.

In the end the old harness was ok other than that one broken wire, but I am still glad I did it this way.

Its great to have the soft close working again.  When it is not, the tailgate rattles.  In addition, the broken 3rd brake light cover, aperture trim and the bottom trim all look so much better.   Now the car goes to the panel beaters to fix the damage from the P-plater earlier this year.

The post S124 Tailgate Wiring harness appeared first on Classic Jalopy.

I’m taking my 1990 Mercedes 300TE on this drive.  Now I could have taken my wife’s modern car – a Mercedes E350 Wagon.    However, I far prefer driving the 300TE.   The E350 is not as irritating as most modern cars, but I would still rather drive the 124.   I also think any issues are more likely to be dealt with easily.   An ECU or Airmatic problem is going to end the trip.

In order to reduce the odds of any issues, I had a few jobs to do to the car.    None of them were mandatory, but I think good preventative maintenance.   I have previously covered some other work I did on the car such as refurbishing the instrument cluster, attempting to change the centre vent and changing the speakers.

This trip should take me past 380,000km for the car.

Starter motor replacement

A few months ago, I noticed that when I started the 300TE, the starter motor did not seem to full disengage, and I could hear a bad noise like it was still just touching the ring gear.  It only did this a few times, but I really didn’t want to be stuck with a bad starter by the side of the road.   A Bosch remanufactured starter wasn’t all that expensive and seemed like good insurance.    I had this done at a workshop.

Tailgate soft close mechanism

The S124 has a soft close mechanism for the tailgate.   All you need to do is gently close it, and the motor will latch the tailgate.   Recently, mine has started play up.   The motor does not engage when it should, but there is a sound coming from the back like the motor is trying to work at other times.   This was mostly when I closed it firmly to bypass the soft close, or when I turned off the ignition.

I bought a second hand soft close mechanism, and gave it to the same workshop who did the starter.   They swapped the two mechanisms over, but it was still playing up.   They also did some troubleshooting.   Using a multi-meter the microswitches seemed to register when the mechanism was in a position, but they did not trigger the motor.   When the motor was triggered, it was at extremely low voltage, and the noise was coming from something else in the mechanism.

After troubleshooting for a bit, and getting nowhere, we agreed to simply disable the mechanism for now, so it doesn’t flatten my battery while I am away.   The car still works, without the soft close feature.

Oil and Filter change

As part of my trip preparation, I did a routine oil and filter change.  My hoist is currently broken, so I pumped the oil out manually.  I used Penrite HPR15 – 15W/60 Full Synthetic.

When I do an oil change, I like to remove the fuel pump relay and use the starter until oil pressure registers on the gauge.  I don’t think its strictly necessary, but its something I like to do.

Bluetooth Module wiring

When installed the correct Becker 1402 in the car, I wired in a hidden Bluetooth FM injector.   This had mostly stopped working.  Occasionally it did work, which made me think the unit was bad.

The Bluetooth unit is under the dash wood in front of the shifter.  I removed the dash wood to get to it, assuming it would need replacement.  When I removed the radio, I immediately saw the problem.    In my install, I used a relay to trigger the blue tooth unit to turn on from the antenna trigger wire.  One of my crimp connections was loose.  When I moved the radio, it came out.  To fix the issue, all I had to do was put on a new connector.

New Battery

When I first purchased the car, my battery tester noted that the battery was a bit marginal.   From the service history, it had been installed in 2017.   It probably had another year or so in it, but in November, Supercheap had a big sale.   I got a new battery for 30% off and installed it for the trip.

Auxiliary fan cut in

I’ve never been happy with the temperature of the car in stop/go traffic with the A/C on.   It sits just above 100C.   Since I owned the car, I put in an 80C thermostat and replaced the viscous fan coupling.  Those made improvements, but I it was still hot in traffic.   Given the properties of R134A, I find that it works better if the radiator is not that hot.   I’ve planned to make a fan controller box with a variable resistor like I did for the 560SEC.   However, I’m terrible at soldering, so I have not had time.

For this trip, I just wrapped the resistor around the pins for the fan sensor, and put a new plastic housing around the pins for the wiring.   This is not perfect, but should bring the fan engagement point down to the mid 90s.

Key spare parts

One advantage of driving a very common car, like a Toyota Camry, is that there are parts available wherever you go.   This is not the case in a 30 year old Mercedes.   I packed a few parts that are probably not necessary, but may be helpful on the road.     The first is a new serpentine belt and tensioner.   As a rule, I don’t like serpentine belts.  If you lose an accessory, you can’t just remove that belt and continue.    However, that is what the M103 is equipped with.   This is not something I can do by the side of the road, but having the right belt and tensioner means I can be towed to any garage for a belt change.

I also brought a voltage regulator, and a distributor rotor and cap.   Plus a few standard Mercedes relays, fuses, some wiring, cable ties and basic tools.   I take more when I go on the road trips with my friends, but I have a whole boot available, and we are pushing the cars harder.

I managed to get all this stuff squeezed into the side storage areas in the cargo area.

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