9 replies to this topic

[simplyminis]

Ok I have a rev counter in my mini it's a 80mm and works fine
I want to down size to a 52mm I have bought 2 gauges of people on here the one won't work and the other as soon as you start the car goes to max revs??
Any idea thanks

[tiger99]

Well, how are they wired? Were the wires the same number and colour as the originals, and joined up accordingly? Were those that don't seem to work originally used on Minis?

 

There should be a positive feed from the "white" circuit, in-line fuse optional, an earth (black), a connection to the dash lighs for illumination, usually red, or red with another colour, and the signal lead from the coil negative, which should be black/white. Check that it is on the correct coil terminal, same as the black/white to the distributor.

 

Do you have electronic ignition, or points?

[simplyminis]

Electronic ignition but I have a rev counter that works I'm wondering if it's something to do with the clocks??
Bit strange how 2 of the same clocks don't work

[tiger99]

They could both be faulty. Stranger things have happened, and everything breaks eventually. But check the earth carefully, that is the thing most likely to differ between instruments of different size. In other words, the earth wire may be iffy, and the large one may have been earthing through its mechanical fixing, while the smaller perhaps not.

 

Diagnosing electrical problems like this at a distance is a bit hit and miss, because there is not too much to go on. Sometimes, when such and such a light does not work, but something else does, it is possible to be more exact, but here I can only suggest trying the non-working tachos in a different car, with different ignition, i.e. points, because that may be the problem with some instruments.

[RossKnight]

The one that goes straight to red line, is it an RVI rev counter by any chance?

Edited by RossKnight, 31 January 2014 - 03:40 PM.

[simplyminis]

The large one works and it's not fixed it's just resting or in my hand! I've added another earth to the smaller ones.
The one just doesn't work
The other the needle goes straight to the limit

[dklawson]

You have not mentioned which two brands/models the small 52mm tachs are.  Any chance you can provide that and/or (preferably) pictures of them and their wiring?

 

In general, for MOST modern aftermarket tachometers you will have at least four wires with the basic color codes of:

Black = earth,

Red = Switched +12V (fusing optional)

White = illumination, and

Green = Sense

 

Don't worry about the white illumination wire until the gauges are working.  The green wire should go to coil (-) for a modern voltage sensing tach. 

 

Again, the color codes above are general and typical for modern aftermarket automotive tachs.  Other equipment such as marine tachs and off-road equipment gauges often use different colors. 

[simplyminis]

no idea on the makes off the top of my head

I dont think im getting the colours mixed up as im using the wire off my current working rev counter 

 

I have also double checked which one is live neutral and the one from the coil

[dklawson]

I assumed your working 80mm tach was a Smiths unit.  If it is, Smiths uses wire colors tied to the Lucas wiring scheme.  Aftermarket tachs do not follow that standard.

 

Note that I said an aftermarket tach will typically have a green wire going to coil (-).  With a Smiths/Lucas scheme it is tyically a white/black wire connected to coil (-).  Also note that with Smiths/Lucas wiring, white (unfused) or green (fused) is the +12V supply  ... on the aftermarket tachs, red is typically for +12V.   In short, if your working tach is a Smiths unit don't assume its wire colors have any connection or similarity to the wires on the small 52mm aftermarket tachs. 

[simplyminis]

no its not a smiths and the wires are additional so not colour correct si i  checked with a bulb to give me what the wires were. 

Bulb on - live

bulb flickering etc im positive its wired correct