hello. for a month agoo i installed a switch for my extra backup light.
i did connect worng cable to wrong place. to did blow the fuse.
changed the fuse. but after that happends. the car drains for power after standing for couple of days-
did never had that problem before.
did meassure the backup wire, and it gives out 0,16 V when not in reverse. guiess that is just sleeping power in wire.
but what should i check? ennoying!

 

You need a wiring diagram to identify what wrong wire you connected to so you can trace it back to what component you possibly damaged.

 

To hopefully prevent you from adding to the present problem,

We don't know what year vehicle you have, so we have to stop there, but if it is a late model, it has modules that receive a command and then send the message to the component to do the desired function. These modules have protective measures within them and when something pulls too much power, to protect the system ,IT SHUTS DOWN and needs to be reset. We cannot always add STUFF to a system these days because they are not designed to be altered.
Even if you wired an addition to the electrical system directly, the charging system gets affected because all that is monitored to prevent problems and now a can of worms has been opened.
You might consider having an experienced shop handle this for you.