Battery Disconnect Switch

[freemist]

Would using one regularly as a method of turning off the car cause damage to electrical components? 2000 bmw 323i

Thanks

[curtis73]

It depends on how your alternator is wired. Simply disconnecting the battery might not shut the car off if the alternator is still feeding the ignition. If it does, then yes, it can cause pretty serious damage. The alternator can fry, and the electrical noise created without a battery to suppress it can do pretty serious damage to the rather delicate Bosch components.

[shorod]

What are you really trying to do here? Are you looking for an added anti-theft measure so you'd be disconnecting the battery when the engine is shut off and the key already removed? Or are you strangly looking for a way to kill a running engine?

If the prior, there are other options. One is to rely on the likely already installed anti-theft system. The systems used in this vintage of car are generally pretty good. Another option would be to install a fuel pump cutoff so you can disable power to the fuel pump via a hidded switch. This setup would be easier to hide than a simple battery cutoff switch and would not reset learned parameters of the PCM and the emissions readiness monitors.

If you go the route of the fuel pump cutoff, I'd suggest a small toggle switch controlling the coil of two parallel high current relays. This way if one of the relays fails, you don't have to immediately worry about the system leaving you stranded. It's a bit of redundancy, until the first relay fails and you don't realize it, then the second one fails. This would be pretty unusual though.

-Rod

[Moppie]

A mate used to use a fuel cut off switch hidden in the center console under a pile of dirty tissues