Wiring harness - Tehcnical question.

[Ess14]

This may seem like a noob post to some, but it's not one that is easily searched for..

Scenario:
My wiring harness is all quite chopped up in various places and it's really a crappy wiring job top to bottom on my highly modded and electrically modded SR 240.

So I'm thinking about re-doing the wiring, which means buying a new wiring harness and installing it so I can finally wire everything up nice and neat.

But I don't really know about the actual 240 wiring harness, I don't have the FSM or wiring diagram for the car, but I have ripped it apart and done some wiring as I am probably more knoledgable in that field than any other.

So - is there only one wiring harness for the whole car? Does it start at the ECU? The wiring behind the dash is the Fed up portion, so that is what would be benefitted.
How hard is re-wiring this with a wiring diagram? If I am wrong on anything, explain how it works if possible, and if I am right - the same :)

Thanks again zilvians.

[Gramentz]

You should download both the SR and KA FSM first.

[projectRDM]

S14 I take it.

There are at least six wiring harnesses in the car. 96+ have seven, ABS cars have an additional one too.

1) Underhood harness. This begins inside at the SMJ and the steering column and runs out under the hood through the driver side fender well, across the core support, to the main fusebox.
2) Dash harness. From the SMJ, this harness runs across the dash to the other side.
3) Roof harness. From the base of the passeneger side Apillar the roof harness runs up into the roof, to the sunroof and domelight.
4) Subharness. This runs from the SMJ down the driverside rocker panel, across to the shifter, and back to the rear deck.
5) Tail harness. From the rear deck this runs around the back of the car, to the lights, and then to the fuel tank.
6) Engine harness. From the F3 plug, to the ECU, then out under the hood to the engine.
7) EVAP harness. Running from the ECU down the passenger side rocker panel, this goes into the trunk under the rear deck and plugs into the tail harness.
8) ABS harness. Runs the same way as the EVAP harness.

Replacing a single harness is simple, unplug everything and remove it, then install the new one. The only issue you'll run into is there are several versions of each harness depending on year/trim/options.

For example, there are five different subharnesses depending on options, OE security, power antenna, and the amplified sound system. The dash harness is worse, with up to 12 versions depending on year model and options.

S13 is slightly less involved since it uses a single 'body' harness, replacing the need for a dash, sub, and tail harness. There's also less options that changed. But it's more work to swap too.

[g6civcx]

Like Russ said above, it's fairly simple once you learned how to read wiring diagrams you get in the FSM. Rewiring the body is doable if you take your time.

The hard part will be finding wiring diagrams for an S13 SR. You can d/l an S14 SR and KA FSM from zeroyon.com.

The best way to do it though is to use a Painless wiring kit or something of that nature. You can rewire the whole car and eliminate all unnecessary wirings. But that would require a greater understanding of electronics. Still, I think you can do it if you take your time.