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Q&A Turns signal circuit questions.


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So this is all regarding my '70 240Z's wiring. Although most of what I'm going to ask is just going to be universal Datsun knowledge. 

My turn signals don't work on my 240. Hazards work very weirdly. Flash very fast, then slow down slightly. Then fast, then slow. ALL bulbs are working with no corrosion in the sockets. After running the flashers for a moment, the flasher gets HOT along with the wiring and starts to smoke slightly. Seems like a short, but no obvious wiring issues that I've found. 

Now something I'm not used to is this style flasher. It's a Signal stat 175 flasher two prong, similar to the canister ones I've found on later Dattos. Not sure if it's stock or not, but the car is pretty much 100% original. 


Rather then having a plastic 2 prong plug like every other Datto/car I've ever owned it's got two female spades. Is it possible that this flasher could be connected backwards causing a short? Or the 44 year old flasher could just be shot? 

Seems to me that if there was a short in the vehicle harness it would simply just flash SLOW (since the flashers are load based) rather then fast which typically happens at low load, like when a bulb is burned out. 

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This is based on my knowledge of a 521.   The four way flashers, and the turn signals share the turn signal lights, and some of the wiring.

the turn signal wiring is routed through the four way flasher switch.  If the flasher switch is off, the turn signal wiring is on.  And the other way around, flasher on, turn signals off.


The flashers are in series with the switches, and lights.  More load on the flasher, the quicker it heats up, the faster is flashes.  A short circuit adds load, and makes the flasher go faster.  If your flasher is getting hot, and the wires are starting to smoke slightly, that is three clues you do have a short circuit somewhere.


Hopefully you have a 240Z electrical diagram. look for interconnections between the turn signals, and four way flashers.  if you have that interconnection, get the flashers working first, then get the turn signals working.

If it was may car, I would next remove all the turn signal lamps (bulbs), and see if the fur way flasher still clicks.  If it does, you do have a short somewhere, because I do not think the indicator lamps should load the flasher enough, to make it get hot enough to flash.  If the flasher still clicks on and off, and the indicator lamps flash in the instrument cluster, it may be possible the short is located under the dash, or in the instrument cluster.

Instead of removing turn signal bulbs, it might be easier to unplug the turn signals, where the body wiring harness plugs into the lamp assembly wiring harness. 

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Hey Daniel, looks like the circuitry seems to be pretty similar between the 240Z and other Datsun's. 

Interesting, I always thought that the flashers were generally faster with LESS load (why they flash faster when a bulb is burned out.) The hazard switch seems to be the common connection between the turn signals and hazards so I need to back trace some of that wiring. 

The down side is that so much wiring was cut right out of the fusebox into the main harness it's almost impossible to repair without a donor harness and unfortunately, the '70 Harness seems to be different from any other year and hardest to find. 




I pulled all the bulbs and still get a load on the hazard flasher, so yes, that would indicate a short. I was brainstorming at the beginning here, but it all seems to point right back to a possible short. Probably a result of the crappy wiring done by the PO. 

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