I'm going to check the fuse to see if that is the problem.
Just ran a diagnostic with VCDS and I have two errors one of wich is a comunication error with the auxiliary heating and the second error has something to do with CAN central comunication 1 wire (hope I rememberd corectly). i'm hoping it to be a blown fuse as this might turn into something realy expencive.

I've checked the link and the links posted on that topic and didnt seem to find a fix.
I've checked the fuse box and for some reason the fuse for the aux heater was missing. The car was purcased from new and for the first 4-5 years it killed batteries. Somehow the mechanic thaught it would be a good ideea to get rid of the fuse but not fix the problem. All this was at the cost of confort of drive. Untill now I didn't even know that these cars come fitted with a aux heater just because the dont generate enough heat as to properly heat the car and heat foggy/iced windshield and door windows.
The battery on ths car is aprox. 6-7 years old and I think thats how long the aux heater wasn't functioning.

Put in a new fuse, and conected the vcds. Comunication problem with the aux heater has disapeard and its working fine. I mean I get a heated car in 3-4 minutes since starting the engine. On the other hand when i turn off the engine, aux heater runs for another 10-15 second and the runs off but I can still hear a light vibration such as, lets just say a electric water pump. The sound is similar to a house aquarium filtration pump. I think that is what killed the bateries.

Any ideas on how to fix this issue? I have vcds168 and hope that you cand help me adress this issue via long coding or somethig.

Thank you!

After checking all the fuse boxes and checking fuse locations on the web, I found that transporter has two fuse boxes under tha dash first being for the basic equipment found on all T5 and the second being for the optional equipent.
It was rather easy to determine wich is wich since the car is basic and only has AC and Webasto. The second fusebox had about 5 slots that could use fuses.

The optional equipment fusebox is located under the basic equipent fuse box, both of them near the gear shifter.
I randomly swapped fuses until I could determine wich fuse suplied voltage to the "sound", or more precisly the electric water pump. After removing the fuse, checked if I could conect to auxiliary heater using VCDS and it conected. After that I monitord it to see if it functioned and it did but only with the engine on. On road test car blows heat inside the car from the first 1km of extraurban use. No prestart and idiling of the car was done. Outside temp was -8 celcius.
After a cold night, no noticible battery or start issues.

The thing that drains battery is the water pump wich for some reason has hot wire for permanent voltage even when the car is not running. When removing the fuse, pump works only if engine is started. I think that fuse is for cars eqiped with a suplimentary battery and/or for cold region countries as cars from those parts of the world have a exterior battery charger jack to keep battery charged over those cold nights.
I think the purpose of the water pump is to circulate the watter and monitor wheter its needed to start the webasto and keep the coolent preheated to a certain degree for easy start.

Overall, there are about 7-8 auxiliary heater/climate controll fuses in those 2 fuse boxes.

Fuse is located in the optional equipment fuse box, 3rd row(2nd row of larger fuses), first fuse on the left. Don't know the number as I couldn't determine any numbers on the panel.

Edited by 3uga on 10/02/2019 at 19:14