Rep Power: 0

For a 2000 Honda Civic, no modifications, got 200k miles on it but runs great.

Here's the problem:
Heater/fan won't turn on. No power, no lights, nothing. Radio still works and to my knowledge all the other electrics are fine. I went and unplugged a few things right before the problem showed up so I'm almost certain I messed something up and caused it.

Here's the story:
I was driving home from work the other night when the check engine light turned on. That bothered me, so I went googling around to see if I could get one of those scanners and lo and behold I found a youtube video of some guy telling me I can do it with just a paperclip. Great I thought, I'll be done with it in 15 minutes. Well I went out and for the life of me couldn't find the plug the guy in the video was talking about, so I picked the one that looked closest to it and start sticking my paperclip in, turning on the car, and seeing if it works. It obviously didn't, so I start unplugging other things to see if I could find it. I unplugged three cables on the passenger side, all were relatively easy to access, one was small and green with a lot of pins, the other was small and blue/gray with three pins, and the one I stuck the paperclip in was big and brown with four pins arranged in a square. I also went over to underneath the drivers side and opened the fuse box, but I didn't mess with anything over there thankfully.

I tried unplugging and plugging back in everything but that didn't work. I don't know which cable the heater is on or I'd try and examine it a little closer. I guess I probably deserve it for being so dumb but I'm really hoping there's some obvious and easy fix I could do so I don't have to wear three coats when I drive to work. Thanks

 
Rep Power: 223

Hopefully you only popped a fuse. Start checking. A basic code reader is under $20.

 
Rep Power: 211

I've never tried this method on an OBD2 (cars 1996 and newer) Civic, but apparently it can be done per this link: https://honda-tech.com/forums/honda-...lists-1901557/ You were looking for the two-pin (blue) Service Connector. That is is the only method to check an OBD1 scanner. Well, except for an aftermarket device named Hondash, which works really well.

As Colin stated hopefully blew a fuse or possibly a relay? After checking fuses if you don't find anything obvious try an ECU reset by:
1) Turn off all electronics (dome light, radio, headlights, etc..). Engine off.
2) Remove the negative terminal from the battery
3) Turn on the headlights and step on the brake pedal for a minute to discharge all residual voltage. Afterwards turn head lights off.
4) Wait about 10 minutes and then reconnect the negative terminal to the battery
5) Start the engine (all electronics still off) and let it idle for about 15 minutes
6) Test the blower fan and whichever electronics weren't working.

96-00 Under Hood Relays and Fuses diagram: https://troubleshootmyvehicle.com/ho...fuse-relay-box
96-00 Under Dash Relays and Fuses diagram: https://troubleshootmyvehicle.com/ho...-dash-fuse-box