Project Hakosuka: Electricity Hates Me

 

Where we left things last was that the mechanicals were now in good shape, but the electrical system was a little haywire.  Press the brake, and the headlights would come on (but not the brake lights).  Turn on the headlights and the indicators would come on (but not the headlights).  Turn the indicators on and….nothing would come on.

So it was time to put down the spanners and pull out the multimeter and get hardcore with a soldering iron.

Firstly, taking the car apart to see what we have to work with.  There was a lot of patched up wiring (much of which was just twisted and taped and had since come apart).

A lot of the connectors were also quite old.

But the first pleasant surprise was that my initial fears about there being lots of wiring hacks and modifications was unfounded.  Sure, there were vampire taps everywhere and additional wiring, but it didn’t do anything.  For example, there was a wired tapped into a brake light wire, and it was neatly cable tied around the boot as it went into the rear parcel tray.  But under there it was just disconnected.  There was also a wire tapped into the instrument light wire, that led to the headlight area, but it just terminated.  It wasn’t wired up to anything, and it looked like someone started along the path of a wiring hack, and then gave up and taped everything up neatly anyway.  That’s a relief, it means that any issues with the electricals are probably just age-related.

First, the wobbly fusible links block.  Wiggling them made the lights come on and off, so replacing the corroded old copper links with new ones seemed a good place to start.  But it didn’t make any difference and the electricals were still haywire.

The main problem at this stage was that I couldn’t get the headlights to work.  Since I got the car, the high-beams had never worked, so I thought that might be linked.  It was at this point where a good samaritan who had been following the car’s buildup, a fellow Hakosuka owner, contacted me and sent me a factory GC10 wiring diagram.  And it was at that point when everything started making sense.

I had a Haynes manual for the 240Z but looking at the wiring diagram for the Zed showed that it was quite different.  The 240Z doesn’t have headlight relays and instead runs the entire headlight current thru the indicator stalk (!).  Looking at the wiring diagram showed that the Hako actually has wiring that is more in common with a 510 rather than a Zed, in the sense that the headlights are always fed a positive current from the battery, and the relays are switches are actually on the negative side of the headlights.  A very unconventional way of doing things and very much the opposite of what you would have expected Nissan to do.

So the first step was to ensure that the headlight buckets weren’t grounding.  If they were, then the current would go straight to earth instead of thru the bulb.  The stock headlights had some metal locating tabs on them, which had some rubber coating which was peeling off.  So I put some insulating tape on the headlight brackets to prevent any grounding.  I also replaced the headlight plugs with new ones.

That didn’t help.  So the next step was to pore over the wiring diagram for answers, and it looked like the oldschool relays for the headlights and hi-beam flahser grounded through their metal bodies.  So I took them off, and discovered that they were held on by loose-fitting self tappers and had some healthy corrosion at the point of contact with the body.  So I cleaned up the metal surfaces with emery paper and drilled out the mounting holes to replace the self tappers with clean new bolts.

Then flick the headlight switch and voila!  Hi beams are now working too!

I think the problem was just an earthing issue.  Very often when earths go bad, the current finds other ways of getting to ground, and so the electrics often go haywire and you press one button and something else comes on.  So I go and clean all the wiring earth points in the engine bay and cabin, and now the electrics were no longer haywire.  But the indicators were lifeless, and the fuel gauge and reverse lights didn’t work. 

Looking at the wirin diagram again showed that all 3 things were fed off the same fuse.  So it’s time for this to come out:

Now I have to admit that when I look at one of these things, my mind just goes blank.  It’s like picking up a book, turning to the first page, and then discovering that it’s all written in Russian or something.  So a few calls to friends, and they gave me the lowdown on how to test for continuity and power. 

I thought I’d start with the indicators.  According to the multimeter, the fuse powering the indicators/reverselights/fuel gauge was getting power.  The wiring diagram showed that the power then went into this clicker can, and testing the wire for continuity (one side to the fuse, the other to the clicker terminal) showed that the wire was ok with an acceptably low resistance.  But testing the output terminal of the clicker can showed no voltage.  So I replaced it with a modern one, and now there was voltage going thru the new clicker can…but the indicators still didn’t work.

 

Looking at the wiring diagram showed that the fuse in question went to the indicators, and branched off to the reverse lights, the fuel gauge, and then finally to the rear demister relay, where (like the headlights) it was an oldschool one made out of metal that grounded via its body:

I removed it and cleaned up the touching surfaces (you can see my sanding marks) and…voila!  We now have reverse lights, indicators and a working fuel gauge!

 

Not having delved much into electrics before, I do find this all very illuminating (boom-tish).  My mental image of electricals is that you have separate circuits that are all independent.  But now I understand that they aren’t really all that independent, and something as remote as the reverse lights can be affected by the demister…because they are all interlinked.  And it was all mainly due to earthing issues!  I mean, before today, I would have thought that since the whole car is made of metal that earthing would not be such a problem.  But I guess you learn something new everyday!

And this is where we are at the moment.  I have to put the car back together now (the above article actually covers a period of almost a week of working on the car and staring at the wiring diagram!) and the only thing I haven’t tested is the wipers.  But I think we’re on the downhill stretch and can now think about getting the car certified for road use.

Not long now. I hope!