Battery pyro-fuse theory of operation

[anking]

I've recently purchased a 2017 Q5 off of the auction that would not start. Dashboard lights up but no crank.
I realized that the pyro-fuse was the culprit.
The auction vehicle description did state that this vehicle was "run and drive", which is impossible with the fuse being damaged?
On top of that I also found that 3 out of 4 belts were deployed (no airbags deployed).
Needless to say it was impossible to tell just looking at the pictures, and the fact that it was "run and drive" basically stated the otherwise.

I can probably argue the misleading description with them, but i need some documentary proof that the pyro-fuse prevents vehicle from starting if any of the airbags or SRS components deploy.
Does audi publish this information in any of the vehicle manuals, or is this available anywhere online?

Thanks!

[S4'ed]

That is correct. The battery pyro fuse is blown if any airbag (or belt tensioner) is fired. The car can be started if you use a heavy wire to jumper across the pyro fuse terminals. You can also move the heavy wire that's on the pyro "output" lug, to an available lug on the other side of the pyro, which is connected directly to the +12V positive terminal post of the battery.

I am not sure if there is an "official Audi" statement in the Factory Service Manual describing the operation of the battery pyro.
You can get 90% of the content of the factory service manual at ALLDATADIY.com, for a small subscription fee.

[anking]

That is correct. The battery pyro fuse is blown if any airbag (or belt tensioner) is fired. The car can be started if you use a heavy wire to jumper across the pyro fuse terminals. You can also move the heavy wire that's on the pyro "output" lug, to an available lug on the other side of the pyro, which is connected directly to the +12V positive terminal post of the battery.

I am not sure if there is an "official Audi" statement in the Factory Service Manual describing the operation of the battery pyro.
You can get 90% of the content of the factory service manual at ALLDATADIY.com, for a small subscription fee.

This is exactly what i did, i just used a heavy jumper wire to verify that it starts and it does. I just want to explain it to the seller that the ad was misleading and now it is going to cost me much more to get everything fixed (replace belts, clear crash data, etc...)

Also, was it possible to jump start it using the battary connections under the hood? Are they directly connected to the starter?

[eljay]

In case you still need one, I have these: https://www.audizine.com/forum/showt...ash-pyro-fuse)