Disconnecting battery for installations

[i_4got]

Hi guys, so I recently tried installing LED switchback turn signals. This included installing a new flasher relay. After plugging in the new flasher relay, the lights just kind of went haywire. My lights wouldn't turn off, my high beam signal was on, my hazard lights didn't work, and I couldn't get my car out of "Park" gear. Now I'm a complete noob at this stuff, so I was certain I messed something up.

The techs at Toyota told me a fuse was blown out. From what I deduced from posts here, I should have disconnected the battery first. So here are my questions:

1. Did I blow my fuse because I didn't disconnect the battery before installing the new flasher relay? If I disconnect the battery, and retry installing the new relay, will I avoid this problem again?
2. How do I disconnect the battery? (I know, I know, it's a complete noob question but forgive me, nobody's taught me before). I know it has to do with disconnect a wire from the negative terminal? Can someone post a clear pic or something to help me out with this?
3. What other maintenance/intallations require disconnecting the battery first? I'd like to avoid another scare like this in the future. I thought I killed my car.

Thanks!

Also, my car is fine now.

[Mo707]

1. yes it happened because you didn't disconnect the batter and it shouldn't happen again if you disconnect the battery.
2. Remove the negative wire. (I believe)
3. Anything that involves wires or electricity you would want to disconnect the battery.
This also happened to someone else on this forum so dont feel to bad.
And please wait until someone else can conform this before trying again.

[paaji]

Always remove the negative battery wire first. Positive is optional.