I'm a bit into this topic recently, as I'm just adding an auxiliary heater to my car (actually 2 of them :lol: ).

One if them is completely home made system - 650 W electrical coolant heater, based on 2 glow plugs dipped into engine coolant and controlled by AKKU voltage and ECT using AtTiny13A microcontroller.

The other one is Eberspächer D3WZ - a 3,2 kW diesel powered aux heater. Almost everything on Eberspächer is similar on Webasto too, so many things are in common.

Eberspächer and Webasto heaters are capable of OBD - using one wire K-line, W-line, and in some BMW's, rovers etc even K-bus. Those that are in cars from factory are usually wired to stock A/C controls, and K/W-lines are found on the OBD port - although usually not in the same network with engine ECU. The W-Line from the Webasto FBH uses the same signal levels as the K/L protocols, but does NOT conform to the ISO/KW protocol standards as it is a protocol used only by Webasto. Normally it can be found on pin 7 or 8 - it depends.

There are several wiring diagrams for K-line - COM port interfaces, but OBD connection can be established with any K-line - USB interface. But there are some catches as OBD port pinout -it can be different for different brands of cars (usually there are adaptors out there), bitrate (usually 9,6 or 10,5 kbps - still searching, will try tommorrow) and diagnostic software. The communication can NOT be established using ELM327, as it discards all data that it does not know/understand/recognise, so it assumes this data is invalid.

Webasto has a nice little freeware program called Webasto Thermo Test. I had a bit trouble finding it, but now I got it (attached with diagram of an interface).

Eberspächer also has a freeware diagnostic program called Eberspächer EDiTH, it can be found here: http://www.esparofmichigan.com/techsupport/pdfs/Diagnostic%20Software/

In a couple of days, I am about to finish my Aux heater (FBH - fuel burning heater) project. I'll report.

Well, it is confirmed that Eberspacher D3WZ 25 1998 communicates on 2400 bps, but I didn't manage to establish the communication. :thumbdown:

ECU is in lockout mode so I have to delete some DTCs to unlock it.

Using the terminal, I can see data flow on all of my K-Line interfaces (using oscilloscope), but EDiTH software does nothing - none of the versions, not in Win98 (VMWare), not on WinXP compatibility mode (dual boot) and not on Win7 64-bit compatibility mode (dual boot).. Will keep trying. :oops:

Otherwise, I'm waiting to get my PCBs done, so as soon as a CNC machine is free for an hour or so, I'm starting to make my own ECU and timer/controller/LCD on AVR platform. :thumbup:

I managed to connect to vw t4 d4ws ebespacher using autocom interface/sw.
I replaced the d4ws unit with a 2009 mercedes vito d5ws one.Looking on schematic seems the same.But autocom does not want to connect.Also selected mercedes variant in the sw using the cabble conected to the vw.Still no results.I am curious where in the obd does the t4 have the diag line vs mercedes.

Usefull tutorial about diagnostics with Eberspächer EDiTH and connections is here:
http://www.club-nissan.ru/forums/showth ... p?t=297582
Text in Russian but translate.google.com or other will help.

THX!!

Looked in my old cables box and found a kkl cable.Got the edith sw and will try it.
Spend some time today using autocom with mercedes car selected and swaping eberspacher diag pin inside obd2 plug on the car from pin nr 7 to other pin locations inside the plug that merc uses as k line for some controllers.No luck.
Does someone know if merc uses the pin nr 7 inside obd2 connector as k line for eberspacher as vw does?