The signal from the AC control panel arrives on the CAN bus/OBD.

Looks like switch that disables AC in case of low pressure was fiddled with by someone who broke off the retention clip and "fixed" it with a zip tie. So thats the next suspect that gets investigated.

Temporarily reassembled this mess... but was interrupted by rain. Can't run the engine with some plastic covering the currently non-waterproof front of the car. Moving parts, hot etc...

So I switched the reverse light switch and its connector last week.

Indeed, the parking brake was unhappy about the inconsistent signals.

Reverse light works again.

ASR is happy after driving a few meters.

Apparently there is the option for TPMS but they are not fitted. Ok, I dont care.

Apparently there is a short for the steering column lock sensor. I will ignore this one for now.

The #iCarasoft thingy can show/plot the climate request signal. As the fan blew 100% in the meantime but just for 1 day I assume the climate controls have a bad CAN bus contact/loose connector.

Please applaud my elaborate oil filling contraption. I spared no expense and bought a new funnel.

Yay Indeed, the switch AND the connector were bad. And the transmission got new oil, while at it.

The switch indicates reverse (pin 1 white and 2 yellow bridged) and neutral (pin 2 yellow and 3 brown bridged).

This explains the "catastrophic electric handbrake meltdown service immediately" display in case the car is on a red light in idle. The car wants to engage the electric brake but is missing this signal and is soooo sad.

Hmmm... why is the connector for the magnetic clutch unplugged and grinding on the drive belt?

If plugged in, and driven by a lab PSU I hear a click and it draws ~50 W.

So I guess at least the magnetic clutch thingy and wiring is good.

So I need to debug this at the CAN bus level and see why it does not switch on.

As the replacement connector for the reverse light switch will arrive next week I can stop here for now, and do a fun thing. Like watch paint dry...

The #Renault #Scenic II saga continues.

Yay, I got the correct reverse light switch.
Nay, there is a bad contact in the connector in addition to the original reverse light switch not working.

Done:
- replace protection and switching unit (original one is fine)
- fix unit connectors (someone damaged the old ones)
- get new cover/enclosure (someone broke the old ones)
- replace battery mount bolts (had to drill them out due to rust)
- replace headlight bulbs (they failed, just to annoy me)
- derusted (left) wheelhouse mounting bracket (most rusty part on this car I am aware of)

TODOs:
- paint wheelhouse mounting bracket
- replace reverse light switch connector
- test new reverse light switch with new connector
- replace reverse light switch in gearbox
- swap gearbox oil
- debug AC magentic switch (the thing that started all of this)
- mount towbar + wire trailer outlet
- mount bumper, headlights, ...

Lol, the headlight bulb just decided to die at the exact same time I swap the unit. It decided to turn into a 5,6kOhm resistor, leading me in the direction of a bad contact somewhere... Its required to remove the bumper and headlight to switch it anyway... so I'll just replace both now.

Wiring from the unit to the reversing lights is fine.

Schematic for wiring to the reversing switch is inconsistent. The pinning and wire colors do not match between control unit and the switch itself and Renault placed the 3rd pin on a completely unrelated schematic page for maximum confusion.

The reversing switch seems to be dead - no contact between any of the 3 pins.

Gearbox oil will spill out if I remove the switch, so first I want to try a new switch outside of the gearbox and see if the reversing lights work again... and figure out the right spot to put the gearbox oil back in.

This does not explain the AC not working, but I'll tackle the issues one after another.

Ok, so I replaced the broken connectors/wiring. The car goes to sleep after 15...20 minutes, which is good.

I tried the old and a new unit.

Result: Old issues still remain, plus left headlight stopped working, and the car says "ASR off" which just seems to be normal after unplugging the battery for a few days and should go away after driving some distance.

Good news:
1. most likely its not the unit itself (or the other one got the exact same issues, which is unlikely).
2. now something else stopped working, indicating that I am at the correct spot.
3. with the additional connectors I can now build some debug cables

Bad news:
Looks like I need to drink a lot of red wine to get to the same state of mind as the Renault engineers 20 years ago.