B7 Climate Control and Engine Start/Stop dead after heavy rain

[buzzmaster]

Hi all,
I am really scratching head on this one.

I think I'm dealing with multiple problems, but perhaps they're all related.

I live in Brisbane and over the last few days we had some seriously heavy rain and my 2014/15 Passat TDI 2.0 Highline was out in it and parked facing downhill and she sprung at least one leak.

When I started her yesterday morning there were 3 problems that I noticed.

1. The reversing camera system didn't work (bluetooth and stereo fine, but no camera signal)
2. The dash lit up with "Engine Start/Stop Error" - and yep, the start/stop functionality is not working. This error just appears whenever I stop at lights, but the engine keeps running.
3. Most importantly - the entire climate control system is completely dead. In an Australian summer, this is what I'll be rushing to fix. It's not just the control panel lights either. There is no functionality. i.e. No fan. No rear demister.

The reversing camera problem is sorted. Kinda.
I followed this information and found my camera control module was swimming in about 15mm of water in the boot. I dried and cleaned the board but it seems to be completely fried, so I'll end up buying a second-hand one and I've taken steps to lift the unit up to higher ground, plus I've modified the rubber seals around the boot arms to hopefully prevent future leaks. It’s raining again today, and that seems to have worked as everything is still dry.

The Start/Stop error and the climate control problems I feel are likely related to one-another, but I don't know where to even begin with these problems.
I very much doubt they're directly related to the drowned reversing camera controller, but perhaps someone can confirm that or please point me in the right direction.

I immediately thought it must be a blown fuse, however I pulled and checked every single fuse in all 3 fuse boxes (right side of dash, left side of dash, and engine bay) and none of them were blown. I haven’t found any other water leaks or wet patches of carpet, but I won’t rule them out. It seems likely that there’s more water somewhere. Is there a separate controller unit for the climate control somewhere? Is there yet another fuse box?

At the moment I'm stumped. I love this car, but the idea of living through a Brisbane summer without air con is not something I look forward to.

I would seriously appreciate any and all suggestions to how I can diagnose and fix this.

Could someone also please point me in the direction of a fuse box diagram for my car? Mine is the B7 variant (late 2014/early 2015 with the HID headlights) I can't seem to find a fuse diagram that is accurate)

I will be thankful for any help.

Cheers
Col

[MIG]

This PDF has most of the wiring; fuse box locations are flipped on our models.
Volkswagen Passat B7 - Wiring Diagrams -vw-passat-b7-wiring-diagrams-eng.pdf

Do you have a trailer module? it and the AC controller sit on the convenience CAN bus. The other side may have got water ingress too


How is the battery voltage? The water may have drained the battery while it was shorting out.

[Lucas_R]

Have you checked the condition of your battery? If your battery is on its way out or simply low on charge then you will have all sorts of weird electrical gremlins in the car, and the start/stop system is one of the first things to be disabled when the battery is low on power.

I understand you may not be able to hook up a battery charger while its raining, but if you have one, when it stops raining id be hooking one up or at the very least taking the car for a 30 min drive to put some charge in the battery.

[Guest001]

This will help with ALL diagrams for a B7 Passat Just sort through it as I downloaded them all into the same folder



Update your browser to use Google Drive, Docs, Sheets, Sites, Slides, and Forms - Google Drive Help

[buzzmaster]

Hi guys. Thanks for all of your responses.

Yes, I do have a trailer module. I haven't hooked the trailer up, but will try on Friday to see if it has power to the lights.

The battery seems fine. I have driven the car for several hours yesterday and today. All seems good, plus it's a relatively new battery. The battery connections are solid. The car has been driven each day for a few hours, but just to be sure I will charge the battery today.

I removed the glovebox to get to the Convenience Control Module yesterday.
The Convenience Control Module itself seemed dry, but the fabric cloth wrapped around the wiring harness was definitely damp, so water did get behind the dash. Not much, but there's obviously a small leak or seepage which makes me think this whole problem is definitely water related. I just need to figure out precisely what component/s are affected.
I sat the CCM in the sun for a while and I dried out the wiring with a hair dryer before reassembling everything.

Thanks heaps for the wiring diagrams and manuals! You guys are super-helpful.
I also finally found this fuse box diagram for the B7:
Fuse Box Diagram Volkswagen Passat B7 (2011-2015)

Some things make me think I'm looking at a blow fuse, but I've checked them all, and some things make me wonder if I may be dealing with a dead relay, but I'm not sure how to diagnose. I'm hoping it's not a dead CCM, but I would expect all of it's features to be kaput, not just some.
Overall I'm still stumped, but determined to solve this.

I've ordered this ANCEL VD700 OBD2 scanner to see if it can give me any clues.

I'm really hoping to free up some time in the next few days to keep looking, because I really want to get this sorted.
If you have any ideas, let me know.

I really appreciate the assistance so far!

[buzzmaster]

Another symptom that I just noticed is that several automatic convenience systems that normally rely on sensors to activate are now on by default.

The radiator cooling fan is on full-time as are the headlights if set to the Auto setting and so are the auto-sensing wipers (they are now just intermittent timed wipers)

🤔

[MIG]

That almost sounds like a few different issues; the BCM is in control of the wipers and headlights.
I think you are on the right path; you need more data to track down the issue; scanning this car is a good start.

Even checking powers and grounds at the climate control unit would also be a thing to check.

[buzzmaster]

It was actually a simple cause, and an embarrassingly simple fix - a blown fuse - caused by a water leak, a short and an oversight on my part (and in part, poor design)


I'm putting the solution up here simply because I want the next person to know what to look for.


The cause: The reversing camera control module was absolutely fried by the water leak in the boot. This resulted in the camera module shorting out and causing fuse number 15 (10A) to blow.
This fuse is shared between the reversing camera module, the climate control system and multiple other systems, as listed below.


Rain and light sensor -G397-
Heated rear window relay -J9-
Heated windscreen relay -J47-
Climatronic control unit -J255-
Air conditioning system control unit -J301-
Reversing camera system control unit -J772-
Control unit for terminal control and engine start -J942-
Remote control receiver for auxiliary coolant heater -R149-
Tyre Pressure Monitoring System control unit -J502-


Now, I'm old school, so the first thing I went looking for was a blown fuse, and I actually pulled and checked EVERY fuse in the car, but obviously I didn't check closely enough and missed this one. Grr.
Only when I found none to be blown did I go looking for other problems.


The solution: Unplug the reversing camera module AND LEAVE IT UNPLUGGED, otherwise it will blow new fuses too! Replace the blown 10A fuse and enjoy the cool, cool air after sweating for a week without it during a Queensland summer.


The further solution will be to ensure that it doesn't happen again, so I'm plugging these water leaks.
I've actually found two sources. The first was the terribly over-engineered seals around the boot lifting arms that I found had collected leaf litter and blocked the drainage hoses causing an overflow around the seals.
I've removed the factory seals and used my laser cutter to fashion some new ones out of neoprene that completely seal around the arm when the boot is closed, AND don't cover the drain outlet.


Unfortunately I've also discovered water leaking in through one of the taillights in the boot lid, so I'm going to have to pull this out and have a further look to rectify this.
However, it's all looking good.


Once I get a new reversing camera module, it will all be sorted.
I'm thinking to not, and instead put the money towards a new stereo head unit that is Android Auto/Apple Carplay enabled.
It seems most aren't compatible with the factory camera module, so I may just save that money.


In any case, thank you to all who offered help.


Cheers,
Col