Bonnet shut detector

[bmwz3tower]

My Z3's battery has been draining recently. So I'm looking at all the possible offenders.

There's what seems to be some sort of detector for the bonnet, I've looked at photos of other z3s and they don't see to have so I'm thinking it was fitted as a part of the auxiliary alarm system. Here's the photos:

 

[Rudyrov]

My 98 has one but it is a little different in appearance, I agree it's most likely for the alarm .

 

[Duncodin]

Mine also has one. It's a rectangular switch that slots into the rectangular hole.

If I'm not mistaken the switch, in the bonnet closed position, is open circuit. Circuit is closed (causing the alarm) when the bonnet is opened.

Not sure it should be draining the battery in either open or closed position.

My battery drain was the passenger seat foreward/backward switch stuck in the 'back' direction. But that drained completely flat overnight. If your drain is slower than that then it won't be the seat motor.

 

[t-tony]

Time to put your phone on record on the boot floor and close the lid. Unless you already have. It's the most common cause of Z3 battery drin.

Tony.

 

[Mint]

Agree with the above comments. What you have is an aftermarket switch. Original is rectangular like @Duncodin says. If it fails it does cause the alarm to go off rather than draining the battery.
The original looks like this...

 

[bmwz3tower]

I've just tried the boot light, and it's not that. I've has a battery monitor on it and it's a rather slow drain so probably not the seat motor. Thanks for the advice

 

[ExMX5owner]

I've just tried the boot light, and it's not that. I've has a battery monitor on it and it's a rather slow drain so probably not the seat motor. Thanks for the advice

Time to pull fuses one at a time then, whilst watching the battery monitor... That being said, I have on occasion had a battery or two that doesn't hold a charge.. A small drain on the battery with ignition off is quite normal too, clocks, anti theft etc.. not enough to discharge a battery quickly though.. If you have a multi-meter that measures amps, you could also pull the fuses and test across them "ignition off" to see how much and where any significant drain is going...