So I've searched on many different forums with people with the same problem, and tried all the solutions others have said to try, and have not solved the problem.
I have a 1994 Civic Dx Hatch, swapped with a d16z6 from an ex coupe, as well as the entire car harness (for power windows, locks, etc. This was completed in August of 2019, and I have had no problems until yesterday.

I went to start my car and notice that the dash lights weren't on, as well as the taillights and front parking lights. So it was obvious that fuse #19 was blown. I replaced it and turned on the lights, and it popped. I tried a couple of times before deciding there must be a short.

- I started by disconnecting the harness leading to the rear lights, located on the driver side behind the driver's seat. Still popped the fuse.
- I removed the bulbs from the front corner lights. Still popped.
- I removed and unplugged the radio. Still popped.
- I removed the clock and hazard light switch. Still popped.
- I removed the gauge cluster. Still popped.
- I unplugged the dimmer switch. Still popped.
- I attached a test light to fuse #19 and turned the light switch to on while I moved the wire harnesses underneath the dash, and the test light remained lit.

I don't know where else to look. The harnesses were wrapped in a fabric tape that is hard to rub through, so I couldn't find obvious cut wires that are grounding themselves.

Theres a junction after fuse #19 called c507, which has a few red/black wires that light up instrument bulbs and other bulbs. Is there a way to test continuity on those wires? If so, how? Anything else I need to check? The interior is pretty much all apart. And I need to find this problem by tuesday because I need to go back to college. Thank you.

 

im having the same issue in my 2007 civic 2.2 diesel.

 

I actually never figured out the source or cause of the problem. I ended up removing basically everything from the interior and plugging in components and reinstalling the interior until the fuse no longer blew, and ended up having all my interior back together with everything functioning properly. My best guess is a part of the harness was grounding somewhere and by removing and installing the interior moved the part of the harness, wherever it may be. Because your car is a diesel, I'm assuming your model is non-us, so I may not be too much of a help. However, you can start by unplugging major harnesses that correspond with that fuse, whether it's the harness that goes to the engine bay, behind the dash, or back to the rear of the car. If you unplug one and the fuse no longer blows, you can know that the harness you unplugged has a problem somewhere and you can start there. Make sense?

 

Hi buddy, no not US, UK.
I’ve managed to sort it thankfully. Required a lot less work than what you had to do. Turned out that the fella I bought the car off had installed 12v LED side lights rather than standard and it was to much for the relay. I’ve now but normal 501 bulbs in and everything is sorted.
T’was a bit of a panic though.

 

Makes sense. Luckily it was something small and you were actually able to find it lol, my electrical gremlin could just be on vacation, hopefully it wont come back.