Master battery switch as good as disconnecting the battery?

[Guest]

Just a quicky, and this will probably sound like a novice question. Obviously whenever you carry out any electrical work on a car you need to disconnect the battery, but as the title suggests, is simply switching off the master switch as good as?

[Jonathan Kay]

No, it isn't. You would still have 12V between the battery positive, the feed to the switch and anywhere that is earthed.

 

Relevant 7FAQ describing why you disconnect the earth side of car batteries.

 

Think about this for any work, not just electrical. It also describes the hazard of tools contacting the battery directly. People have various rubber covers etc protecting against this.

 

Jonathan

 

Edited by - Jonathan Kay on 28 Mar 2014 19:28:34

[andy_h]

Sounds like you need an Engineer 😬 😬

 

In theory yes as the master switch is supposed to cut all power as it's a switch between the battery and everything electrical. However, some people wire things the battery side of the switch such as battery charge sockets (cigarette lighter socket). So as long as yours doesn't you should be fine

 

Cheers,

Andy

 

[andy_h]

Cross posts 😳

 

JK is correct, the cable from the battery to the master switch will still be live, but everything else after the switch should be dead.

 

If you're working under the dash then safer to disconnect the battery as the back of the master switches are not covered (protected) and you could short it out if you're throwing spanners around under there.

 

 

 

[Guest]

Thanks for that Jonathon, very informative read!

 

Quoting andy_h: 

Sounds like you need an Engineer 😬 😬

 

😬

 

Edited by - Smiffy7 on 28 Mar 2014 19:52:25

[Ozzy]

Come on Guy's!

 

Surely everyone should experience the joy of welding your spanner to the battery/bodywork, at some point in their lives