25 replies to this topic

[purple_fly06]

Hi,

I am in the process of wiring up my dash but i believe the loom is for a 2 clock dash, so regardless of the loom how would i wire it up?

At the moment the only wire i have is the female bullet which plugs onto the male bullet, so from the image and text below i am assuming that it is a 12V power source coming from the ignition barrel. But when i have tested it, the wire going to the dash is coming from the coil, so i believe this is wrong. And that instead it should be coming from the Ignition barrel.

I have done some research an have found this (I do have an RVI tacho):

RVI 1275GT Tacho
Male spade connector - 12V IGN Source (white wire)
Small Screw below spade connector - Earth (usually via screw into PCB)
Female bullet socket (next to screw) - Connection to coil +ve (white/green wire)
Male bullet (above female) - 12V IGN Source (white wire)


Would it be possible if you could tell me if i am correct but i believe IGN is Ignition and i know that coil +ve is the positiive side of the coil, but i dont know what PCB is.

Also is the image & text above correct or will i have to wire it up differently.


Thanks

Josh

[purple_fly06]

I think PCB may be something Circuit Board

[purple_fly06]

oh, and if it helps i do have the 3 clocks and the complete circuit board that will also cover the tacho.

[Algordo1100]

Yes PCB is printed circuit board.

You need to either use the PCB from a 3 clock set up, or solder some wires in to take a live and earth to the unit for its operation and illumination.

Using the PCB is far simpler. And yes IGN is ignition source (live that turns on with the key) If you use the PCB you dont need to worry about this as the multi connector carries it.
depending on the year of your car, the live from the coil may already be on the loom and just sitting there redundant. this is certainly the case for the mid eighties to early nineties models that I am most familiar with. citys etc didn't have tachos, mayfairs and coopers ect did, but the loom is the same.

So that wire from the coil is there ready for you, sitting there with a bullet connector on it If I recall.

Al

[purple_fly06]

There is a wire just sitting there but instead of connecting to the female bullet socket it pops onto the male. its almost as if the wrong connector has been put on it.

Could that be what has happened as i have tested the wire at the coil and at the dash end and it is the same wire, but it seems to be connecting to the wrong bullet.

Josh

[Algordo1100]

its possible. The later looms have a female bullet on that redundant wire if i remember right. Im assuming your car is a later one? The female bullet connects to a male on the back of the nippon seiko clocks. The Gt clocks may be different but I cant remember and im at a resteraunt so i cant go look

[purple_fly06]

I believe that it is a later loom in an earlier car so i think your right.

when i go back and look at it it will swap the connection over to a male add in the rest of the wires and see if it works.....or blows it up

[purple_fly06]

I just tried wiring it up and i put all of the wires where they were supposed to go.

when i touched the white on the IGN barrel the car cut out, does anyone know why this is? The tacho didnt even flicker

Is it because the coil is wired the wrong way or could it be that the wire that goes to the female bullet has been wired to the wrong side of the coil?

Thanks

Josh

[jpw1275]

Is it electronic ignition? If so you need a rvc tach not riv, riv are for points only I believe.... That maybe your problem

Cheers james

[dklawson]

I didn't know that RVI tachs were ever used as stock in Minis.

An RVI tach is different from modern tachs. First, as James said... RVI tachs do not like electronic ignitions and typically will not work with them.

Second, RVI tachs are current pulse sensing, not voltage pulse sensing like a modern tach. Therefore, they expect all the power to the coil to pass through the tach. Since your last post states that the engine was running until you touched a wire to make the last connection, the wiring is incorrect. The two bullet connectors on the tach are a path for all the coil current to pass from the ignition switch to coil (+). With those properly connected the engine will start and run even without the tach receiving power.

In the wiring table you included in the first post you will note that it says that the male bullet goes to a terminal on the ignition switch. The female bullet goes to the (+) side of the ignition coil. Any other wires on coil (+) will have to be disconnected. Also, make sure that your white/green wire that is supposed to go to coil (+) IS going to coil (+) and not coil (-). On modern tachs the sense wire would be on coil (-). If your white/green really ends up on coil (-)... the tach won't work and the engine will not run.

[purple_fly06]

Is it electronic ignition? If so you need a rvc tach not riv, riv are for points only I believe.... That maybe your problem

Cheers james

Yes it is electronic ignition.

I didn't know that RVI tachs were ever used as stock in Minis.

An RVI tach is different from modern tachs. First, as James said... RVI tachs do not like electronic ignitions and typically will not work with them.

Second, RVI tachs are current pulse sensing, not voltage pulse sensing like a modern tach. Therefore, they expect all the power to the coil to pass through the tach. Since your last post states that the engine was running until you touched a wire to make the last connection, the wiring is incorrect. The two bullet connectors on the tach are a path for all the coil current to pass from the ignition switch to coil (+). With those properly connected the engine will start and run even without the tach receiving power.

In the wiring table you included in the first post you will note that it says that the male bullet goes to a terminal on the ignition switch. The female bullet goes to the (+) side of the ignition coil. Any other wires on coil (+) will have to be disconnected. Also, make sure that your white/green wire that is supposed to go to coil (+) IS going to coil (+) and not coil (-). On modern tachs the sense wire would be on coil (-). If your white/green really ends up on coil (-)... the tach won't work and the engine will not run.

So your saying i need to find an RVC tacho at some point and wire it in to this :

RVI 1275GT Tacho
Male spade connector - 12V IGN Source (white wire)
Small Screw below spade connector - Earth (usually via screw into PCB)
Female bullet socket (next to screw) - Connection to coil +ve (white/green wire)
Male bullet (above female) - 12V IGN Source (white wire)


RVC 1275GT Tacho
Male spade connector - 12V IGN Source (white wire)
Small screw nearest male bullet connector (top right in photo) - Earth (usually via screw into PCB)
Male bullet - Connection to coil -ve terminal (usually white/black wire)

Josh

[Dan]

Why when people are trying to fit a non-standard part, and find it doesn't fit straight in, do they assume all the stuff they are fitting it into that is already present and working in the car must be wrong or incorrectly built and bodged by the manufacturer in the first place?

RVI and RVC tachos are completely different as Doug says, only the early 1275GT was fitted with an RVI tacho as standard. Your car is wired for an RVC tacho, and RVI will not fit straight in without you having to change things. If you go to the trouble of fitting it you will probably find it doesn't work anyway because as said they aren't really compatible with electronic ignition. When you get an RVC tacho you will wire it like an RVC tacho, not like the RVI method you have quoted here. It's hard to know what wiring you have already, you haven't mentioned any wire colours at all and that is what we need to know about. In a 3 clock dash the RVC tacho gets its earth and its lighting supply from the instrument PCB. It gets its power from a flying lead near the instrument multi connector which is light green/orange. It also gets a signal from the LT, negative side of the coil on a white/black wire. If you were to connect the ignition power to the coil negative by trying to force an RVI tacho into this setup without sorting out what wire is what first, then the car would not run as you would be bypassing the coil entirely.

[purple_fly06]

who ever had my mini before me totally messed up the loom, there are wires missing, wires disconnected... hence why i just want to know what i need to wire up a tacho regardless off the loom.

When i used the wiring diagram to trace wires, the wires arent even there or they are a total different colour.

From what i have read i will need an RVC Tacho instead of my RVI that i currently have, and i will need to wire it up like an RVC, this is because of my electronic ignition.

And this is the correct wiring for when i put in a RVC Tacho:

RVC 1275GT Tacho
Male spade connector - 12V IGN Source (white wire)
Small screw nearest male bullet connector (top right in photo) - Earth (usually via screw into PCB)
Male bullet - Connection to coil -ve terminal (usually white/black wire)


Josh

[Dan]

Sorry, didn't realise your car was so messed up.

Yes that is the way, RVCs are simple. The ignition source to the RVC tacho is rarely white though. It's on the accessory circuit as standard with the wipers and heater so it's light green/orange. If you were to put it on the ignition circuit then white would be correct, but are you designing the wiring compleetely from scratch or are you following a standard diagram for a specific year?

[purple_fly06]

When it comes to the wiring of the car the wiring is really messed up, and im no electrician.

and i will be designing completely from scratch, not bothered about following the correct diagrams, just want it to work.

thanks