What's going on here?

Combine the following attributes:

• Newly acquired Volvo S80 2002 with a diesel heater (Ardic)
• Cold and hostile environment.
• Moderate amount of free time (but never enough!)
• Reasonable coding skills and electronics know-how
• Hatred of cold and snow

Mix them in a blender (figuratively) and what you get? Desire to construct a remote control for the diesel heater! Laziness is indeed a major motivator for comfort zone aficionados.

My Volvo does have a timer for starting the heater, but I my schedules are almost never fixed, and what I would rather do in my mornings is to press a button, sip coffee and watch behind a window how my Volvo gets warmer, instead of going there to set it on manually. Hence the project in question.

Now, the quest started with basic Googling: what is already available, have other people done something like this before and how much do they cost? Volvo does offer OEM remote heaters, but they cost shitload of money. Not going pay a hefty amount of 600-1000+ euros for a simple remote control and a box that hits a switch. My hacker soul laughs - challenge accepted.

I've decided to document this project, not only gather my thoughts, but also to share any bits of information that I might find. I hate re-inventing the wheel as much as any other coder, so if this ends up helping even one person trying to figure out their Volvo innards and hack their Swedish tanks, writing this might not been in vain.

My plan was to build a prototype using Arduino (open-source microcontroller) and XBee (low-cost radio module). I've been messing around with Arduino for quite a while, but wireless experience I do not have. However XBee is supposedly quite easy to program and is well documented, so I won't anticipate huge problems in that area. Besides, it's fun to expand your field of expertise. In this case to two new fields: car automation and wireless communication.

Other DIY guys have been thinking alike: 

• A guy called VP (link here) has made a reasonably nice device: SMS-controlled heater starter which uses AVR microcontroller and GSM-module. 
• Similar project (finnish only, sorry) using SMS-controller relay (Celotron centro)
• Another one (finnish & english)

However to control the actual heater, all of the above mentioned devices rely on AEM (Accessory Electronical Module) to do the dirty work. AEM is a 150-200+ euro Volvo accessory that  offers simple voltage-based on/off interface for non-official, non-Volvo external accessories, such as alarm systems, parking assistance, handsfree systems etc, and of course remote heater starters. AEM then connects to the car's internal electronic system (CAN bus) and controls other devices in the car by sending them CAN bus messages. Thus, external devices don't have to know how to talk to the aforementioned devices directly but can use the simple interface offered by AEM.

Again, I was definitely not going to go out and spend money on a device that just turns the heater on when being told so. I'm both cheapskate and stubborn. So, my only choice was to find out how CAN bus works by a humongous task of googling, researching and reverse engineering the message traffic, and ultimately perhaps finding out how to control the heater. Then design and construct a prototype for sending the ignition command. Then add wireless modules and build a remote. Then press button, sip coffee and watch my Volvo get warm.

Sounds like a lot of work? Sure. But even risking having frostbites after hours of hacking outside in cold temperatures, I'd rather do that than empty my bank account and pay a horseload of money to a guy behind the counter in order to fast-forward to the coffee sipping. Did I mention stubborn?