Ok, update time.
Parts (climate module and pressure sensor) arrived from @enuff_zed this morning, cheers mate! So of course I tried it as soon as I could, delaying lunch by an hour and angering the wife. Oops. I disconnected the AUC sensor (just in case it's at fault), and plugged in the new module.
Nope.
I then left the original sensor in the system hooked up the one he included just sitting in the engine bay and still also read 0V - I'd assume something even at atmosphere. Hooking it up out of the car to a source does show some voltage, so I think both switches are fine. At this point, I'm really frigged as to what the issue could be :? . It's highly doubtful that TWO modules and TWO sensors are not working ok, so really, I have to suspect the wiring or other electrical gremlins _somewhere_.
Aside from that, some more interesting notes.
- Both fuses (F22 and F39) for the climate module are ok.
- The new climate module seemed to light up and work/control just fine but it does throw an additional code for the aux. water pump, which my m54 engine doesn't have - so the module will work, but there will be errors without coding the feature out. No biggie.
- I used ISTA to engage the compressor manually (you can do this for 8 seconds at a time). This _actually works_, I see the clutch engage and I can feel the cold kick in, so there is pressure in the system for sure and the compressor isn't dead! Component eliminated for now.
So, what next? Honestly, I'm not 100% sure. To 100% rule the module out, I would need to de-pin the 3 wires for the pressure sensor AND the 2 sense wires for the AUC sensor, which I don't have the tools or know how to do (yet...) but that should allow me to read 5V from source/return on the module. Given I've had 2 modules now behave exactly the same, I doubt it's this.
To 100% rule the sensor out, I'd need a more reliable hookup of 5V to it, my *cough cough* dodgy battery packs joined together are a bit of a hack. Always wanted a nice bench power supply anyway so I might just buy one! The AUC sensor I don't care about right now, so will probably leave it disconnected for the foreseeable.
I saved the best til last. I have a new code:
Code:
LSZ2: Headl.v.a.c, front load sens, sh.circ.to earth
. Now *this* is interesting. I'm off to do more research into these circuits. I wonder if they share a ground and something's amiss with it...