25 replies to this topic

[minituga]

Hello
As some of you know I'm from Portugal.
I'm just finishing my mini but I do'nt know how co connect the Rev counter, the voltsmeter, the ammeter and the clock.
Can someone help me please?

[dklawson]

There are many "unknowns" in your questions... at least they are unknown to me.

First, how old is your Mini? What year was it built?

Second, what type of instruments are you adding (Smiths, TIM, VDO, other?)

Speaking in the most general terms, late model and aftermarket tachometers are voltage sensing. You connect them to 1) chassis ground, 2) switched +12v supply, 3) the coil (-) terminal, and 4) to the dash wiring circuit for illumination.

Volt meters are very simple. They connect to chassis ground and to a switched +12v supply. They don't draw much current so they can be connected to just about any dash wire that is controlled by the ignition switch. The lamp gets wired to the dash wiring as the tachometer mentioned above.

The clock is similar to the volt gauge, but it must be connected to a non-switched +12v source. The lamp gets wired to the dash wiring as the tachometer mentioned above.

Again, without knowing what gauges you're talking about I can't offer specifics. In general you should consider it a necessity to borrow or buy a volt-meter to locate switched and non-switched connections for your gauges.

[minituga]

Thanks for the fast reply.
All the gauges are smiths but the clock that'sveglia. My car is a 1980 mini 1000 with a 1974 - 1275 engine. The rev only has one connection to be made?
What kind and thickness of whire should I use?
I was told the volt-meter should be connected to the alternator, is this correct?

[dklawson]

Over here we specify wire size by "AWG" which will have no meaning to you. Hopefully someone in Europe will reply to this thread with wire information. Regardless, none of the wiring needs to be "heavy" or "large". These devices do not require a lot of current.

Please look at the face of your Smiths tachometer for model identification and tell us whether it is marked "RVI" or "RVC". Regardless of type, the color codes for the Smiths tach will be different from those I listed earlier. The RVI tachometers are wired in series with the power to the ignition coil (two wires) while the RVC are voltage sensing and use a single wire connection to coil (-) as I mentioned earlier. Let us know which type you have.

Are you sure you mean "volt meter"... not "ammeter" ? A volt meter will have a scale from something like 10 to 16 volts. An ammeter will have a scale marked something like -30 to +30 Amps with the needle resting in the middle, near zero. A volt meter can be connected to any switched 12v source and it is not necessary to run a wire to the alternator.

[Dan]

If your tacho really has only one connection then it will most likely be a mechanical tacho. Is there a large threaded boss in the middle of the rear of the unit? Which car is it from? Fitting this to a Mini is not going to be easy, you will need a mechanical tacho fitting kit for A series engines as made by Mini Spares. It is a boss and an Oldham type coupling which fits to the timing cover, along with a drive cable.

[dklawson]

It never even occurred to me that he might have a mechanical tachometer!!! Thanks Dan.

[minituga]

Guys, thaks for the help.
I'm fitting an Ammeter and a volt-meter.
The tacho has 2 connections in the back and something like a spike with a round end.

[Dan]

That's three terminals then!

It would be best if you could stick up a photo but the two Lucar blade terminals are probably supply and ground, and the bullet is the sensing wire (coil negative). There should also be a bulbholder fitting which will need wiring in.

[minituga]

and that supply and groun where do I connect them to?

[Guess-Works.com]

Just to an Ignition live wire, and earth...

[dklawson]

Minituga, take a look at this link:
http://www.mgcars.or...dy_rvc1410.html

Is that the back of your tachometer (or similar)? As Dan said, the "round" spade lug is the coil (-) connection, the flat spade lug is for switched +12v and the case needs a good ground connection.

You also said that you're fitting an ammeter AND a volt meter. Why? Frankly, ammeters are somewhat dangerous in a car with a decent alternator. The volt meter is safer and can generally tell you as much information. I'd choose one or the other, not both.

[minituga]

Here's a photo of the back of the tacho.

[Dan]

Looks like a late MGB unit. Just the same as the one DK put up but with a blade for earth instead of using the pillars. The blade that is rivetted to the casing gets earthed, the blade that is in the black bit gets 12v non stabilised fused instrument feed and the bullet gets coil negative.

The big hole needs a bulb holder fitted into it for night illumination which will need to be wired into the light circuit.

[minituga]

I don't know if I can find a switched wire for the volt-meter, as I don't know how.
What if I connect to one of the light bulb wire?

[dklawson]

Finding a switched 12v wire isn't hard. (Yes, you can hook things to the dashboard illumination... but then your volt meter and tach will only work when the lights are on.

Make a test lamp. Take a light bulb (like from a turn signal) and attach a length of wire to its brass shell. Then wrap the connection with tape to insulate it. Leave the center contact tip of the bulb exposed. Strip about 10mm of insulation from the "other" end of the wire attached to the bulb. Go to you car's fuse box and look for connections with "green" wires. Touch the stripped end of the test lamp wire to the fuse box terminal for one of these wires, then touch the center tip of the test lamp to chassis ground (like the metal part of the alternator housing). The lamp should be OFF. Have an assistant turn on the car's ignition and repeat your test. The lamp should be ON.

Make your "switched" connection to a terminal that is OFF with the ignition turned off and ON when the ignition is on. Be sure to put inline fuses on the wires to all your instruments.

I'm not trying to be insulting... but if you aren't sure how to find a +12v supply for your gauges... it would be best to NOT use that ammeter. Ammeter wiring is much more dangerous than the simple voltage connections necessary for clocks, volt meters, and tachometers.