Connecting my tacho

[Eric2205]

Hello,

After a lot of trouble with my ignition I decided a while ago to remove the electronic ignition and install breakers. For lack of time I gave this task to a mechanic.
Since the car runs, although I find that there is a lot of rattling especially when starting when the engine is very hot (may be a new rocker adjustment is required).

My problem is that he changed some wires and he did not reconnect my tacho

Connecting my tacho




This We will like to work on this subject. Searching the forum I found the following schema
Can you tell me if it is correct for an ignition with breaker and without eureka wire?



I understood that the round female connector must be connected to the + terminal of the coil
But I do not understand how to connect:
the male round connector : + tacho feed in ??
the male flat connector : + ingnition power to tacho



Thank you for your help and your explanations

[Old and Slow]

Yes, your first diagram is correct.
The current that flows into the coil goes into and out of the tacho. The two bullet connectors marked +Coil and ??? on your diagram are the connections for this, they are male and female so that you can simply connect the two wires together to bypass the tacho (should you so desire).
The bullets make up a current loop into a transformer inside the tacho, and if you get the bullets the wrong way round you won't do any damage as they aren't polarity-sensitive; it just won't work the wrong way round.
The spade connector also marked ??? is the power to the electronics for the live feed, and the earth return should be a tag under one of the two thumbscrews fixing the tacho in place.
Hope this makes sense, good luck getting it working again.

[Eric2205]

Hello,

I understand and I will try to connect my tacho next we

thank you so much

[Eric2205]

Hi,

This morning I tried connecting my tacho....

On the engine bay there are two wires : a green and a red


I connected the red at the + terminal of my coil


I connected the green at + terminal of my battery


first problem the lamps: ignition and handbrakes are on ... without the key and without the contact


I started the engine without problems and the tacho worked.... but just few seconds


But I could not turn off the engine with the key ... I had to disconnect the green wire of the battery

After this problem I checked the wires
- The green wire is the green wire that is connected on my tacho to the flat terminal
When the ignition is on, there is 12V on the green wire

- The red wire is the wire connected to the male terminal of my tacho

I do not know what to do ?

- Is it normal to have 12V on the green wire when I put the contact?
- Do I have to change my red terminal wires? So that the wire of the female round terminal is connected to the + terminal of my coil?

Help please !!

[scimjim]

This diagram isn’t right.

4C634C7F-0D75-4B2B-B2BD-7F219D10A201.png (89.86 KiB) Viewed 2089 times

The two wires coming from the battery are wrong. One should be ignition fed (from the ignition switch), the other should be a fused supply from the 50A ignition fuse. If you have one of them live with the ignition off, you will power the coil, so the engine will continue to run.

[Eric2205]

Hi Jim

I followed your advice: I connected the green wire to the fuse box (fuse 50A)
No more problem to turn off the engine
But my tacho does not work. When I start the engine the needle moves but as soon as the engine is running it's over

[Old and Slow]

As they say, assume - makes an ass of "u" and "me"; I'd assumed your diagram was diagrammatic - the power source being the ignition switch and not directly to the battery.
If the tacho needle moves off the stop and then falls back when you try and start the engine then it is most likely the electrical interference caused by the starter motor. You still don't appear to have the feed to the coil going from the ignition through the tacho, or as I said above, the two bullets are the wrong way round. Unlikely though, as the bullets are male/female and normally it wouldn't be possible to plug them in the wrong way round.
What colour wires are connected to the tacho bullets?

[Eric2205]

Hi Philip,

My mecanic fit two new wire for male/female tacho bullet, same color for the two wires : red

In my engine bay I found a red wire not connected. After test this wire is connected at the male tacho bullet

[Old and Slow]

But if your engine ran OK with the red wire from the tacho NOT connected, then you already have a live feed from the ignition switch to the coil.
If you take this live feed wire off the coil and then connect the red wire from the tacho to the coil, everything should work (fingers crossed). Take care with the connector that you remove from the coil, as it will be live, so it would be best to wrap it in some insulating tape or similar, to prevent it shorting out to earth.
Of course, if re-wiring in this way stops the engine from starting you can easily put things back the way they were, get the engine running, and then start all over again!!
Let us know what happens, good luck.

[Eric2205]

Hi Philip,

I undersatand i'll do more test as soon as possible and I'll tell you what happened

Thank a lot

Eric

[Eric2205]

Hello,

Last night I was able to work on my tacho again.
I decided to reverse the red wires that are connected to bullets tacho
so now the connections are as follows:
- Red wire who was connected to the male tacho bullet is connected to the female tacho bullet => female tacho bullet / + of the coil
- Red wire who was connected to the female tacho bullet is connected to the male tacho bullet
- The green wire connected to the male flat connector of the tacho is connected to the fuse box (fuse 50A)

The engine starts and works, the needle of the tacho move but for me the tacho needle does not indicate good values

https://youtu.be/J9i3vfipVHs

[Old and Slow]

Oil pressure looks OK, but the tacho.....
Looks like some "progress", but not enough just yet.
I'm assuming you still have contact breakers, and on the other side of the coil from the distributor wire, is there only one connection (from the tacho) providing a live feed?
Do you know why the tacho was originally disconnected? Perhaps it was already faulty.
I'm not sure what to suggest next; perhaps someone else has seen this problem before.

[Eric2205]

My tacho was working but I had a big ignition problem: my coil was heating up a lot.
I decided to remove the electronic ignition and the electric fuel pump.
My mechanic replacing the electronic ignition with breaker to install also new wire. I have no more eureka wire.
So I changed the coil for a dry coil without ballast.
Since the coil no longer heats.
As the next day I was going to Scotland with my scimitar he did not have time to connect the tacho.

[Old and Slow]

It seems strange that the tacho was working before, but now only goes a quarter of the way up the scale. This possibly has something to do with the type of electronic ignition you had fitted before; I'm running out of ideas - perhaps someone else on the Forum has a suggestion.