i have a 90 civic si. the previous owner attempted a wire tuck, including the lighting harness. now when pressing the break at times, the directionals glitch, and rpms glitch as well. also, the heater works when it wants to, unless i give it a few knocks. my question is, does the lighting harness have to be a SI as well? or can any ef harness work? and whats the difficulty in changing this harness?

 

what lighting harness??? that doesn't really make sense. if you are talking about the harness that goes to the head lights, that is more than just a light harness. if that is the harness you are talking about then yes it does need to be from a 90-91 civic Si. it's not extremely difficult but it is time consuming. you have to take out your dash, pull all of the wires through the firewall, but since you said it was tucked i'm assuming it is run a different way, so basically you need to pull it into the cabin, disconnect it from all of the connectors under the dash, then remove.

now the problem with reinstalling the new one is that the previous owner attempted a tuck which means that installing the harness in the OEM location means connectors in the engine bay probably won't match up since I'm assuming they tucked the engine harness as well. so you will need an 88-91 Si engine harness.

 

Post a picture or two of that tuck job, maybe it is possible to salvage it. Start checking for continuity, grounded, and crossed wires, etc. I just pulled a harness off 91 si, and I tell you it takes some time and patience.

 

yes, the light harness, you know what i meant. it did have a wire tuck also, but i was having major problems with it, so i already replaced it, with a new oem crx si wiring harness, so i dont really have to worry about the connectors not matching up. ill take some pics as soon as i can. oohh and the harness that im describing, runs through the passenger fender.