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996 Passenger Airbag Child Seat Deactivation Deactivation

Sundayjumper

Spa-Francorchamps
Joined
17 Mar 2009
Messages
312
No, not a typo ! I'm coming at this from the opposite direction to every other thread about it, I'm removing the passenger airbag deactivation bar. Basically, I got all over excited when my daughter was born and had it installed, but nearly four years on she's only been in the car a handful of times and because I'm now fitting buckets I wanted to remove the bar as she won't be going in it any more. She prefers Mummy's Passat :roll:

But simply unplugging the bar brings up an airbag warning on the dash :( It had to be coded into the car in the first place, so I guess it also needs to be un-coded.

*** DISCLAIMER ***

I've read the old threads and realise this topic is a little contentious, so to be clear, do not do this to your car. I'm presenting my experience purely for technical interest. Don't flame me.

*** DISCLAIMER ENDS ***

Going back to my Tuna just to get this un-coded seemed like a big hassle so I started researching what the thing actually does. I found THIS thread by Renntech's "ukchris" so I must give credit where it's due for pointing me in the right direction. That thread proposes this as the schematic:

12421710211907363b.jpg


Now, I'm not strictly an engineer but I do lean that way, and to me those values seemed incredibly specific. There would be a tolerance in the manufacturing of the resistors so I felt the car would only be looking for high/low resistance in the right ballpark rather than a specific value. The nearest single-resistor solution available was 240Ω + 2kΩ. Purchased from my local Maplin for 10p each. It cost me more in petrol driving there & back !

I also needed a switch. A redundant bedroom sidelight gave me this:

12421710211907362b.jpg


So then to wire it up. The 240Ω in series and the 2kΩ switched in/out by the switch. Chop off the connector on the loom and it all fits very easily inside the switch:

12421710211907361b.jpg


And it works. I've removed the OEM deactivation bar and I don't have any warning lights.

I'll reiterate, because I know what some people are like, do not do this to your car. I just thought it was interesting to see how it works.
 
Forgot to add, I took the following measurements while putting it together:

OEM buckle
"airbag on" = 2.24 kΩ
"airbag off" = 253Ω

The thing wot I did:
"airbag on" = 2.21 kΩ
"airbag off" = 237Ω

It could be tweaked to make it a closer match, but (IME) it's not necessary.
 

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