So i am almost finished with my RHD swap to my 1993 Convertible , I used the harness from a 1998 180sx front clip , . i had an sr hatch that i was daily driving , and i pulled the motor out and re wired the engine harness to work witht he jdm body harness again .. i used the whole 180sx dash harness with the digital climate control , but the body harness to the rear end of the car is cut , from when they cut the clip .. so i cut the body harness for the rear of the convertible, and started finding the wires to the rear running/tail lights/license/ blinkers and hazards and what not .. oh and fuel .. well i have the engine running and all the lights to the rear working and blinkers and all, but my gauges arent working .. i assumed the dash connector colors for tach and speedo and coolant temp and all would be the same so i used the usdm clip and wired the clip into the dash harness so it would plug right in.. i used the same cluster out of the car i was dailying and the same back harness . which plugged directly into the jdm dash harness clips and the wires are all the same colors in the same pinouts....

so when i connect my battery and turn my key on the engine light stays on .. the gas light is on and the door light is on, that is it.. the tach doesnt work .. and the coolant temp doesnt work .the back lights dont work when i turn my headlights on. im not sure about the gas gauge until i put gas in or about the speedo because i havent test driven it yet because i need the coolant temp to know if my motor is overheating or not ... when i turn my key off and pull it out, the engine light stays on .. like its getting constant . and it wont turn off unless i pull the battery cable ..

i read something about the (TCU) for the usdm cluster causing the back lights to not function, but i didnt read anything about the rpms or anything else not working .. there's not a clip that plugs into the tcu from the usdm harness.. im wondering if maybe theres is any other relay or fuse that would cause the cluster not the work .. or maybe the jdm harness dash connector wires arent the same .(which i doubt becasue all the wires seem to be a color match)) there are some plugs that dont go to anything that ive found on the dash harness maybe needs some kind of relay or box like the tcu or something .

Ill post pictures of the build soon .

Turns out i fried my cluster putting my radio in , just put a working cluster in , and everything but the speedo and the back lights work . which for now i dont need .. but for those who read the long post sorry and ill post a thread of the build later when i upload pictures .

and for those who run into a similar problem , test out a cluster you absolutely know works.

The backlights should be the TCU.

But does the 180sx harness have a tcu?

The TCU has nothing to do with the rear combo lamps. Do you have brake lights? If so, then the issue should be on the Red/Blue circuit that runs the parking lights for the car. If you have brake lights but no parking lights, I would say that you either didn't hook up the parking light circuit for the rear properly, have a cut elsewhere in the harness, or the connection at the SMJ is messed up. The parking light circuit comes form the stalk, but the stalk is on the engine room side of the SMJ, so it passes through there to run the rear combos. The brake lights get power on the body side of the harness and is a direct line from the fuse to the rear with only the switch breaking the circuit.

If you had a ton of stuff not working, I'd say make sure the grounds are still hooked up properly, but just about everything back there runs through M101 and M125 for grounding.

As for the speedo, you can test that without running the car. You'll need a friend. Pull the VSS from the transmission, leave it plugged in. With the car in the ON position, have someone spin the speedo and check the cluster side for some voltage. Leave the cluster plugged in, otherwise the VSS won't get power as it pulls its power from the speedo. The VSS gains voltage the faster it's spun. If you've got signal on the cluster side, you have a bad speedo. Alternatively, if you have a multimeter than can supply voltage, the speedo will produce about .5V A/C when spun by hand and removed from the harness. Unfortunately, the FSM doesn't list the operating range of the VSS, but if it was working before you swapped the dash harness out, chances are the issue is in the wiring. Yellow/Black and Yellow/Blue on the dash harness are the VSS wires. The speedo gets 12v from the Green wire (as do the tach, fuel, and temp gauges). The 4th wire coming from the speedo is a signal wire to the ECU (Yellow/Green), you can ignore that while trying to get the speedo working.

Thought he was talking about the backlights on the cluster, not the lights on the back of the car. But no clue about a 180 harness.

Heh, I didn't even think about the illumination lights. Guess when I hear back light, I think tail light. The illumination system is tied into the TCU for the cluster unfortunately. Pretty sure he'd notice if the TCU wasn't there since so much of the car is tied into it. Wipers are tied to it as are the door chimes. The seatbelt light is too for when it's on for the first bit you turn the car on. OP, the TCU is located in the driver side kick panel. It's a white box bolted closest to the door. It's right next to the headlamp timer. The circuit in question that carries the illumination light from the TCU is Red/Yellow. Red/Blue is an unaltered 12v for full bright, but the Red/Yellow gets turned up/down based on the illumination control switch (Sky Blue/Purple).