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1973 Datsun Induction Loop Tach and Electronic Ignition
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2024/10/28 14:32
From KZN, South Africa
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Hi, guys. First post here.

I've always wanted a tach in my Nissan 1400 but they are few and far between here and get snatched up so quickly. I eventually found a Datsun 1200 GX someone was stripping and got an OEM induction loop tach from 1973. Unfortunately the Datsun was a non-runner so there wasn't any way to see that it was working but I decided to take my chances.

Anyway, I recently rebuilt the wiring from front to back of my bakkie and deleted the ballast resistor as you don't need it with EI. As recommended on the tech wiki page, I wired the tach in series with the ignition switch and the positive terminal on the coil. Bakkie starts and runs perfectly but no tach reading at all. The tech wiki does say that the early Datsun tach's work with both points and condenser ignition and electronic ignition. However, so many other forms out there say that induction loop tach's don't work with electronic ignition systems?

I tested all the grounds and the separate 12v for the tach and everything seems fine there.

I was wondering if anyone had any other wiring suggestions I could try? My other idea was to swap the points and condenser back in with the ballast resistor just to see if the rev counter even works, but thought I'd ask here first in case there's a simple fix.

Thanks all.

Posted on: 2/17 8:31
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Regards,
Frigid
2005 Nissan 1400 STD ("Converted" to Champ)
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Re: 1973 Datsun Induction Loop Tach and Electronic Ignition
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From Kent, WA
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Interesting problem

Another way to test the tach is to "temporarily" connect it to a friend's old ford/chevy/datsun. Use jumper wires for earth (black wire), battery + (red or yellow wire) and disconnect the wire to the coil and connect to the loop, and jumper the other end of the loop back to the coil. It will work even with a six-cylinder or V8 engine although the reading will be off


The original tach works with Datsun EI, but some people have problems with non-Datsun systems (or incorrectly wired systems). Which EI exactly are you running?

A ballast resistor is needed or not needed mostly by the coil. Some EI coils require a resistor, some don't. You could try putting it back in and see the tach starts working. All EI system will work with a ballast resistor, and the early Datsun EI required a ballast resistor

I would also fit the condenser that came with the EI system

Posted on: 2/23 1:22
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Re: 1973 Datsun Induction Loop Tach and Electronic Ignition
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Hi, DD. Sorry it has taken so long for me to respond to this. Quite a few things went wrong on the bakkie that had to be sorted out before I could revisit the tacho.

I do remember reading something, on the tech wiki, about testing tach's on other vehicles but I don't think that's necessary anymore.

So the question about which exact EI system I'm running is difficult to answer.
It's a cheap Chinese kit that most spares shops here keep. There is no part number on the dizzy itself nor the EI coil. No part numbers on the box. Just a plain brown box. To be honest, I don't even think the coil included is an electronic coil, it might just be a standard coil. The shop I bought it from did tell me to bypass the ballast resistor so I deleted it. I did wire the ballast resistor back in but it didn't change anything. But I'm pretty sure the resistor has failed, the voltage reading at the coil is pretty much the same with and without the ballast resistor wired in. So I just deleted it again.
I'll attach a picture of the kit.
I ran the bakkie with this coil for a few months but two days after my first post it decided that it didn't wanna be a coil anymore and died. Did some research and the most recommended coil for 1400's with EI is the HUCO 110006 electronic coil. It has similar specs to the Bosch Blue coils but we don't really get those here (well, I can't find them).

After changing the coil I noticed that the tacho was reading... something. It sort of slowly crept up to the 500 rpm mark after a few minutes of idling (it's definitely an incorrect reading, the engine is idling at about 950 rpm) but when I revved the engine, it just stayed at the 500 rpm mark. When turning the bakkie off, the tacho dropped to 300 rpm and rested there. It no longer returned to or rested at 0.

So it seemed changing the coil made this whole issue even more interesting. But the carby and the alternator were giving me issues so I forgot about the tacho for a few weeks while waiting for parts and troubleshooting those issues. Last week I decided to go on FaceBook Marketplace to find a used set of rear corner bumpers/reflectors and I hit the jackpot. A guy, not too far from me, posted pictures full of 1400 spares; spares from multiple stripped bakkies. In amongst all the spares I spotted 3 facia boards with the clusters still attached and one of them looked like it had a tacho but I couldn't quite make it out because of the quality of the picture. Messaged him and sure enough it was a Champ speedo (the one with a tripmeter) and tacho, and the best part was that he only wanted R350 (about $19 US) for all of it! These usually for R1 000 (about $55 US) for the tacho's alone! Plus, I've never found anyone selling a tripmeter speedo.

Admittedly, there was some work to be done before I could fit it. It wasn't just a simple swap in. The instrument cluster had 3 issues: First, the PCB was in terrible shape, there were ribbons peeling off so I doubt all the circuits work. Second, one of the pins for the round connector was bent. And third, weirdly it didn't have the light for the brake? It's stamped with 2004 but I wasn't even aware some of the later models didn't come with a brake light? Especially a Champ which was the highest spec? Anyway, I decided to rather just remove the speedo unit from the rest of the cluster and swap it into mine which is in way better condition and has a brake light.
The tacho needle had fallen off so that had to be sorted before fitting it to my bakkie. The tacho wires had also been cut very close to the ring terminals rather than them being disconnected properly from the cluster and harness, and the tacho globe holders were missing. No biggie, just had to make new wires for it and I'm going to use the indicator bulb holders that came with the cluster as bulb holders for the tacho. Just need to go buy another bulb, I'm one short at the moment.

The Champ tacho's are way easier to wire in compared to the induction loop tacho's: 12v ignition to the red wire, B/W signal wire from the negative terminal on the coil and a ground wire. The globes are wired the same for both tacho's.

It works perfectly and matches the interior better than the lighter grey tacho so I couldn't be happier.

Here are a bunch of pictures.

Attach file:



jpg  Distributor Kit.jpg (145.97 KB)
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jpg  electronic-ignition-coil.jpg (49.22 KB)
22858_6815f053a3b4e.jpg 800X800 px

jpg  2025-05-03 at 11.14.49_c74372f0.jpg (158.67 KB)
22858_6815f08aebcf7.jpg 1040X780 px

jpg  Screenshot 2025-05-03 105732.jpg (188.09 KB)
22858_6815f29530820.jpg 1919X1079 px

jpg  Screenshot 2025-05-03 110700.jpg (184.13 KB)
22858_6815f2b0404de.jpg 1919X1079 px

jpg  Screenshot 2025-05-03 110930.jpg (173.14 KB)
22858_6815f2d968829.jpg 1919X1079 px

jpg  Screenshot 2025-05-03 110016.jpg (139.63 KB)
22858_6815f30476cb4.jpg 1919X1079 px

jpg  2025-05-03 at 11.37.29_8b2ad000.jpg (103.51 KB)
22858_6815f313b470b.jpg 1242X1262 px

jpg  2025-05-03 at 11.18.44_1981112d.jpg (154.83 KB)
22858_6815f31f2dcc7.jpg 4032X3024 px

Posted on: 5/3 11:48
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Regards,
Frigid
2005 Nissan 1400 STD ("Converted" to Champ)
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Re: 1973 Datsun Induction Loop Tach and Electronic Ignition
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Nice photos

The 1973 tachometer only needs one wire, the newer ones need three wires. The other wires on there are for the lighting

Posted on: 5/3 18:04
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