I am going to be changing a few bulbs on my Opel Astra's instrument cluster. Part of the process involves disconnecting the entire cluster from the wiring harness and obviously replacing it when done. The cluster contains an Odometer and clock. Would I need to disconnect the battery first, or would turning the car off and removing the key from the ignition be sufficient?
When working on electronics, you are best served by disconnecting the battery. The normal sense of your safety (arcing between hot to ground causing burns) is probably not an issue with this. The main issue is protecting the electronics. Even small discharges of electricity (static or from battery) can fry circuit boards or permanently damage the components. Disconnecting the battery helps to keep these very sensitive items from getting harmed. The simple act of disconnecting the power and/or ground from these instruments can cause the small discharge of electricity which I'm talking about. Note I am saying can ... this doesn't mean you will have this type of discharge. Your equipment would probably be safe 99 times out of a hundred ... but that one time you don't ...