Just acquired my first $400 fixer upper a high desert '91 D21. I've got a front left signal, no power. Signal module indicates burnt bulb, but just replaced all lights and markers. Hazards report normal but signal marker won't light. Two seperate systems means the problem isn't from either on switch. Anyone know if this is the next place to check? Looks like a relay for the lights but I'm just guessing, I'm not a mechanic but I slept in a Holiday Inn a couple decades ago soooo....
https://imgur.com/a/MFiyBpg

This isn't the greatest reproduction, but the only condition that explains the behavior is a broken wire between the blinker switch and the bulb that isn't broken between the hazard switch and the bulb. The WD doesn't tell you where in the harness the flagged junctions are, but the harness must be arranged in some topology that allows it to happen. Trace from the switch out to the bulb and your culprit should be in there somewhere. To prove it out quickly, run a long jumper from the GRY/BLU on the blinker switch to the GRY/BLU on the bulb, if it starts blinking then there's a bad wire between the two.

Disconnect the plug on the signal assembly, test for power in the harness — 2- try connecting a ground wire directly to the bulb socket 3- common feature is a bad connection at the light socket, the pins on the bulb are not properly lined up with the socket also recheck bulb number. 4. Open the fuse box there is a relay that powers the lights - not likely but a possibility being the rest of the lights work 5- Take a test light and check for power at the plug on the TURN SIGNAL flasher. Quick question do the hazard light work on the left signal?

whomadewho wrote: ↑

Sat Apr 10, 2021 6:26 am

Quick question do the hazard light work on the left signal?

OP said it works with the hazards. That eliminates 1~5, the WD shows the blinker switch parallel with the hazard switch and downstream from the flasher.

Here's the simplified circuit without all the WD crap. If the hazards work but the blinker doesn't, the problem can only be in the leg indicated by the arrow. The blinker switch is eliminated because the rear blinker works.

VStar650cl. You are absolutely correct. Kind of thinking if the rear signal is working the left front signal almost has to do with a ground issue or the light assembly. That’s why I would disconnect the plug connector and take a test light and check for power. If the light blinks this would eliminate any further checking.

whomadewho wrote: ↑

Sat Apr 10, 2021 8:03 am

Kind of thinking if the rear signal is working the left front signal almost has to do with a ground issue or the light assembly. That’s why I would disconnect the plug connector and take a test light and check for power. If the light blinks this would eliminate any further checking.

That's a goose chase, everything in the lamp assembly is common to both the blinker and hazard. So if it works with the hazard, everything is left out except the wire between the blinker switch and the front bulb. Like I said earlier, the topology of where those junctions are located is unknown. Without knowing that, it's impossible to say where in the harness to look, but it's likely the problem is under the dash and not in the engine box. Nissan wouldn't run two wires through the SMJ or bulkhead connector to reach the front lamp when they can use just one.

Your right in saying it’s a total goose chase. Armchair guessing without actually looking at the vehicle is tough. Worked on 1996 and discovered a broken wire that goes to the plug that connects to the circuit board.

Yep, been there. On stuff that's really old, forget the wires, sometimes you even find busted or rusted circuit boards.

Also mice especially the ones that help themselves to any available nesting material and the ones that aren’t house broken. Auto body individuals can also be a worst enemy or a nightmare. I replaced part of a door post - floor - complete inner and outer rocker panel never dreamed when I was using the air cutoff saw the sparks generated would cause enough heat to melt the tape and the wiring harness that goes to the ECU.

Oosh, tell me about rodents. Check this out!

topic628762.html

As for body guys, tell me about that too. Just yesterday I replaced an airbag brain on a '16 Rogue after scratching my head for an hour trying to figure out why it wouldn't take a configuration. The DPC gave us the answer, the dumb s#$%@s at the body shop put the wrong brain in the car. Same bunch left the LH seatbelt disconnected and wondered why it had pretensioner codes. All I can ever do is shake my head.

Hey folks thanks for weighing in and I'm surprised as I never got any notifications for these responsed, sorry to you all.

There's some confusion here though and I'll clarify:

All the markers, lamps are new, all including new bulbs that came with the lights. With that said, the old signal marker didn't work, I just assumed it was burned out and didn't bother checking as I was replacing everything anyhow.

The front right signal is the problem, there's no power to it. Neither the signal nor the hazard lights up, however the turn signal indicator flashes there's no power operating (fast click) while the hazards click as if there's no problem reporting to them. (no impaired clicking - which is normal for any vehicle) I've cleaned the column, pulled both modules and cleaned to no avail.

The back right signal indicates there's an issue but the bulb lights up.

This could be an issue with the turn signal module itself as well?

VStar650CL wrote: ↑

Fri Apr 09, 2021 6:37 pm

This isn't the greatest reproduction, but the only condition that explains the behavior is a broken wire between the blinker switch and the bulb that isn't broken between the hazard switch and the bulb. The WD doesn't tell you where in the harness the flagged junctions are, but the harness must be arranged in some topology that allows it to happen. Trace from the switch out to the bulb and your culprit should be in there somewhere. To prove it out quickly, run a long jumper from the GRY/BLU on the blinker switch to the GRY/BLU on the bulb, if it starts blinking then there's a bad wire between the two.


D21 Signals.jpg

I messed up in my explanation and I apologize as you put some effort into explaining your point based on my dumb set up. Sorry.
The hazards are 'clicking/reporting' as normal, the light itself does not come on.

I've been cleaning and repairing as I go along and so far the only thing I found was one of the wires to the connector itself had lost a bit of sheath enough to ground to the frame. I repaired that easily enough but still there's no power to that light. I pulled apart the steering column and was greeted with 40 years of New Mexico ranch. All cleaned on both modules but I got a feeling the signal module itself is faulty.

I've got me a neato little Commercial Electric digital multimeter and just dying to try it out but think i'm more in luck if I just buy the signal module online.

VStar650CL wrote: ↑

Fri Apr 09, 2021 6:37 pm

This isn't the greatest reproduction, but the only condition that explains the behavior is a broken wire between the blinker switch and the bulb that isn't broken between the hazard switch and the bulb. The WD doesn't tell you where in the harness the flagged junctions are, but the harness must be arranged in some topology that allows it to happen. Trace from the switch out to the bulb and your culprit should be in there somewhere. To prove it out quickly, run a long jumper from the GRY/BLU on the blinker switch to the GRY/BLU on the bulb, if it starts blinking then there's a bad wire between the two.


D21 Signals.jpg

I'm self taught in everything so forgive my clunky fumblings here on your diagram but oddly enough I had a feeling that I needed to look at the little blue box on the side fender behind the battery. I'll pry that open and peak in there too.

That's a different story. Since it's RH, you'll be checking the GY/R wires. Check the connectors with a fine tooth comb before anything else, with new lamps they're the next most likely cause. The flasher relay has extra load and it will be hard to tell if it's hyperflashing, so you can validate the wiring between the hazard switch and blinker switch by turning on the hazards and seeing if the signal shows up at the GY/R wire on the blinker switch. If so, then there's a break somewhere between both systems and the lamp, which probably puts it somewhere in the engine box. If there's no signal at the blinker switch, then the disconnect is most likely at a junction inside the cab.

VStar650CL wrote: ↑

Fri Apr 16, 2021 4:41 pm

That's a different story. Since it's RH, you'll be checking the GY/R wires. Check the connectors with a fine tooth comb before anything else, with new lamps they're the next most likely cause. The flasher relay has extra load and it will be hard to tell if it's hyperflashing, so you can validate the wiring between the hazard switch and blinker switch by turning on the hazards and seeing if the signal shows up at the GY/R wire on the blinker switch. If so, then there's a break somewhere between both systems and the lamp, which probably puts it somewhere in the engine box. If there's no signal at the blinker switch, then the disconnect is most likely at a junction inside the cab.

I'll check that relay on the weekend. The new lamp for that marker acts just like the old lamp did so I'm inclined to believe the problem isn't marker related but hey it's possible I had a burned out bulb in the old one and in the new one. We've all heard of weirder right? Thanks for the help and info, appreciated.

Happy to help. Keep us posted.

Solved and in another post but just in case anyone reading this thread, there was a small burring of the insulation on the black (ground) a couple inches back of the lamp connection. A thorough taping fixed the issue entirely.