560SEC Climate Control repairs part 1

When purchased, my 560SEC did not have working climate control.   Not only did the A/C not work, but the heater had a mind of its own, occasionally bursting in to life and turning on full heat.  Curiously for a car that has been in Australia since the early 2000s, the car had not been converted to R134A.

My first step was to see if the system could work.   Overseas readers may not know that in Australia it is illegal to sell freon to the general public.   R12 has not been available for many years.   Therefore, I booked the car into a mechanic who does A/C work to have the system converted and gassed up with R134A.   First steps were quite positive, when the Klima relay was bypassed, the system would blow quite cold if you jiggled the ignition key a little.    That left some obvious repair items though.   I had a new ignition switch (the electrical part) fitted, and ordered a new relay.   I also ordered a rebuild climate control unit.

The old Klima relay and ignition switch

While the ignition switch was out of the car, I planned to put in a new tumbler.   It used to be possible to purchase these from the Mercedes-Benz classic center.   They would then set them up to use the right key for your car.   The part has been NLA (No Longer Available) for years on the W107, but I purchased it for my 300SE about 18 months ago.   In that time, it is now NLA for the W126 except for the 1990/1991 models.

The new freon had dye inserted, so I was able to check if the system was holding pressure.   In general, it was, but there was a small amount of dye around the compressor.   In particular, between the two halves of the compressor.   The mechanic who gassed up the system had seen success with a product that can be added to the A/C system to seal up minor internal leaks.  We added that component and I waited for the relay and climate control unit to arrive.

The Climate control unit is quite easy to fit.   I have done this job on my 300SE when I was troubleshooting its climate control system.   First, the ashtray is removed, then the radio.   The dash panel can then be pulled down and out to expose the climate control unit.

560SEC Climate control

it is easier to remove the connections to the other switches first.   Care must be taken to keep the fiber optic cable with the switch, so the back lighting will work when it is re-attached.

In the series 2 cars, the climate control unit is screwed into the back of the wood panel, and there are two big connectors that connect the unit into the cars wiring harness.

560SEC climate control

I am getting quite fast in removing this part of a W126 dash after doing it quite a few times on the 300SE.  Taking the dash apart also allowed me to fix a few other annoyances.   The first was the illumination of the gear selector when the lights are on.   It is a tiny 1.2w bulb that slots into a hole in the underside of the unit at the front.   Not only was my bulb blown, but it had come out and was floating around in the dash.   The second was plugging in the cigarette lighter properly so I could charge my phone.

560SEC climate control

I had couple of these bulbs in stock, so it was an easy change.   The Ashtray illumination was flickering as well, so I changed that bulb while I was there.   After putting the dash back together, I had a MBCNSW twilight drive to attend.   I had originally planned to take the 250SE, but the weather was rather poor.  Based on this, the 560SEC was the better choice, especially as I could test the Climate Control.

My results were generally positive, but with some more work to be done.  My 560SEC climate control sort of works.   The climate control unit regulated the temperature well, although once or twice it went from cooling to heating.    The new relay worked fine, and I had no problems with the ignition switch.   The three main problems I had were that the A/C just wasn’t all that cold, the centre vents are not working properly, and the electric fan never kicks in for the condenser.  I’m pretty confident that the centre vents will be the vacuum pods under the dash.   That is a job for another time.   As the weather heats up I need to get the electric fan working as the car gets quite hot during prolonged idle.   After coming so far, I also wold like to get the A/C cooler than it is now.

Next step is to take it back to test the freon level, and see if that sealer has worked at all.   I also need to see if the Aux fan will work if plugged into 12v directly.

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