Door open sensing

[andys]

Anyone know how the van knows a door is open? Is it just breaking a circuit somewhere in the doors? Or at the BCM?

Reason is my alarm does not have an interior sensor, which coupled with no deadlocks makes me nervous. I have an idea of cheaply adding one by knocking up a circuit with an arduino and a couple of ultrasonic sensors that when triggered would simulate a door opening and set off the alarm. This could be done for less than a fiver in parts. Anyone any thoughts, or see any gaping holes in my logic?

By the way, I've ordered a couple of door locks with the part nos corresponding to those vans that have deadlocking so I'll experiment with those when they arrive.

 

[Pauly]

When doors are closed it applies a negative to a cable that returns to BCM, there is one cable per door
Cable for rear slide doors pass through passenger seat base then under floor
Tailgate goes through roof then I think down a pillar but not 100% may go down b pillar and through seat as above

Open circuiting any one of these wires will tell the van a door is open

 

[andys]

When doors are closed it applies a negative to a cable that returns to BCM, there is one cable per door
Cable for rear slide doors pass through passenger seat base then under floor
Tailgate goes through roof then I think down a pillar but not 100% may go down b pillar and through seat as above

Open circuiting any one of these wires will tell the van a door is open

That's great thanks, I think my idea will work then. There's only a few cables exiting the driver's door so I'll test them until I find it. I can then get a normally closed relay triggered by the ultrasonic and also put a defeat switch before it to lock the interior sensor out in a similar way to the factory setup. I'll order the relay from ebay now and get started on this later in the week