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1976 Datsun 620 stock Tachometer disconnected.


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1976 Datsun 620 normal cab, longbed. has stock tach in the bezel.

 

there's no clear plug in to connect it to just the plug all the cables from the back of the gauge meet at.

IMAG0446.jpg

 

there's what appeared to be leftover cables from a tach to under the hood. I stripped to  clean connection and crimped screw ring mounts. followed the cables under the dash and they had been cut to a dead end except for the black cable which it crimped into a pink/red and orange stripped cable which appears to go nowhere as it is wadded into a bunch of cables that seem to have no end either except for two a orange and a yellow.

IMAG0447.jpg

 

my first question is with the existing cables can I connect them to the gauge or to a plug that will fit the gauge.

as I am not electrically savvy when it comes to Datsun's yet I am looking for guidance on this. 

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Here are some links that enabled me to hook up the tach in my '72 510 (with matchbox electronic ignition). If you have a points dizzy I think the same tach can be made to work but the wiring may be different.

 

http://elfecc.no-ip.info/510/Tachometer/Simplified_Tach_Hookup.htm

 

http://community.ratsun.net/topic/69800-factory-tach-wiring/

 

http://community.ratsun.net/topic/13454-620-tach-wiring/

 

http://community.ratsun.net/topic/16328-how-to-wire-factory-tach-with-matchbox-distributor/

 

http://community.ratsun.net/topic/57834-tach-install-i-know-its-been-covered-but-i-cant-find-my-answer/

 

One of these links has pics of different style wiring on the back of the tachs. The first thing for you to do is use a mirror and flashlight and see which style you have.

 

I looked at the under-hood wiring on my 510 and I have the neg wire from the coil running to the tach, then a return wire from the tach to the IE module on the dizzy. I suspect a points dizzy does something similar but I'm not sure it uses the neg side of the coil. It may be the wires you have can be made to work but running a couple of new ones from the tach to the coil may be easier.

 

If you can let us know whether you have points or electronic ignition and which style wiring your tach has, someone may be able to give more specific info.

 

Len

 

 

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There were two tachs that will fit the 620 so either could have been put in later and why the wiring plug is all fucked up. If this was the correct one it would simply have been plugged in to the stock harness.

 

You probably have the inductive type which is wired in line with the negative coil terminal. The '76 used a single wire from the negative side of the coil.

 

 

 

tach.jpg

 

I'm guessing this is the one you have. Wire #4 / #5 is a single wire between the distributor points and the coil negative terminal. Any power going through the coil passes through that loop on the back of the tach which 'senses' it to give the reading. I don't know which side goes to which but if it doesn't work swap 4 and 5 around.

 

1 is likely ground

2 is power the rest are lamps.

 

Oh hi Len.

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I wired the same tach into my 620 and only much later found the harness plug. Would have helped with the power and the illumination. I would still have to run the loop of wire from coil to tach and back to distributor.

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'76 tach harnes plug...

 

Black ground

Black/Green switched power

Red.Blue and Red/Black lighting. I just grounded one and paired the other with the switched power (Black/Green... so what if it was on during the day??

 

That's all you can use from the harness. You will need to disconnect the distributor wire to the coil negative (-) terminal and connect a wire from it, to the tach #4 wire and one from the tach #5 wire to the disconnected distributor wire. If tach fails to work swap #4 and #5, it's backwards) The tach must be wired in line between the coil and the distributor.

 

To the tach, single dual or EI distributors do not matter. All the same.

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is my gauges the only thing supposed to run to the ignition? cause I have two wires mounted to each bolt on the ignition and the secondary thing next to it. will post pics soon. also so I take it I cut off the black harness plug since there's nothing to connect to and splice either red/blue or red/black in with black/green? then run both of those to the positive cable to what? the ignition?  then extend my ground wire to the tach to plug number 1 yes?

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datzenmike - I was hoping you would give a simpler answer than I posted and you did. I'm pleased to say my tach is still working great. Not so much for the fuel/temp gauges. They work or not on a particular day, I guess according to their mood. I need to take the gauge cluster out again and clean the surfaces where it gets power from the dash circuit board.

 

76Lil Hustler - I don't know if a 620 wiring is similar enough to a 510 for this to help, but read posts #5 through #9 about finding the connector to power the tach.

http://community.ratsun.net/topic/69800-factory-tach-wiring/

It is well hidden way up under the dash but I found it on my 510. Your 620 may or may not be the same.

 

For the power wire for my tach, I used the one to the radio. I initially used one on the connector I found but I think it is for the clock and is hot all the time. The draw from the tach would cause a dead battery after a few days. You want a hot wire that is switched off and on with the key.

 

Len

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taking my cable off the battery terminal for long term parking sure beats not having a tach. at this point im just scratching my head at what the fuck the last owner was doing. there's whole wads of wires all spliced into each other that don't even look hooked up to anything at all. also not sure if I can just find a plug in for my tach so I may just wire it up based off what I think mike is saying. waiting for confirmation before I go cutting wires up but yeah that's the idea.

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taking my cable off the battery terminal for long term parking sure beats not having a tach. at this point im just scratching my head at what the fuck the last owner was doing. there's whole wads of wires all spliced into each other that don't even look hooked up to anything at all. also not sure if I can just find a plug in for my tach so I may just wire it up based off what I think mike is saying. waiting for confirmation before I go cutting wires up but yeah that's the idea.

 

That sounds like a good plan. Just hook up temporary wires to be sure the tach is working. Ground and power to #1 and #2 in the pic datzenmike posted. Wires #4 and #5 hooked to wires that go out to your coil. For those you may be able to use a couple of the ones the previous owner installed although you may want to yank that mess out and replace with new ones. I'm running #14 gauge wires out to the coil but someone suggested #12 gauge is better. I'm not sure what gauge your mystery wires are but make sure they are at least #14 gauge.

 

It is one of the facts of life that if a previous owner has screwed something up, it will be wiring. It is almost a necessity of Datsun life to learn the basics of automotive wiring. A multi-meter is nice but a simple test light helps a huge amount in tracing power.

 

Len

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Already covered.

 

'76 tach harnes plug...

 

Black ground

Black/Green switched power

Red.Blue and Red/Black lighting. I just grounded one and paired the other with the switched power (Black/Green)... so what if it was on during the day??

 

That's all you can use from the harness. You will need to disconnect the distributor wire to the coil negative (-) terminal and connect a wire from it, to the tach #4 wire and one from the tach #5 wire to the disconnected distributor wire. If tach fails to work swap #4 and #5, it's backwards) The tach must be wired in line between the coil and the distributor.

 

To the tach, single dual or EI distributors do not matter. All the same.

 

 

You may have noticed that the 620 dash lights are on a dimmer and no one in the history of 620 has ever needed to dim their dash light. In fact there are about 8 posts on how to add LEDs and what not to brighten them so you can read the odometer. So if the tach is wired directly to 12 volts it is NEVER going to be too bright.

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what was posted sounds like splicing 5 wires together when you say you paired them with the green/black ground. wouldn't that make for an extremely hot wire? I'm just not understanding the phrase used. trying to be precise about it all since its only the 3rd time I've had to mess with car wiring.

I can add extra wire to run the lights power if that's better in the long run for the truck.

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IMAG0452.jpg

 

The solid Red wire is likely the 12 volt source for the tach. Connect the Red wire to both Red/Blue wires. Connect the Black wire (ground) to the two Red/Black lamp wires and the lights will be on any time the tach is on.

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  • 4 years later...
On 8/26/2017 at 9:33 AM, datzenmike said:

That's all you can use from the harness. You will need to disconnect the distributor wire to the coil negative (-) terminal and connect a wire from it, to the tach #4 wire and one from the tach #5 wire to the disconnected distributor wire. If tach fails to work swap #4 and #5, it's backwards) The tach must be wired in line between the coil and the distributor.

Hello again! I'm trying to wire in an inductive loop tach into my '92 Sunny truck and I'm having issues finding the right wires to make it work. I know it's different from a 620, but I assume the wiring should be roughly the same.

The confusing part to me about this is the wiring from the distributor. I have mine ran from the positive side of the coil into the loop and then the other side to the ignition barrel black and white wire. I got some movement out of the needle, but it doesn't read my idle or anything like that. I'm running out of patience and I'm about to throw a generic tach that wires straight to the negative side of the coil or buy a super expensive 620 tach that just uses the one wire to the negative side.

Can any of you guys help me out?

http://datsun1200.com/modules/myalbum/photo.php?lid=2708, if this link works this is how I currently have it wired into my truck.

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