tacho not working

tacho not working

Hi i was just wondering if anyone could help me out,
i have recently purchased a 1976 mini clubman s with a 1275 engine and electronic ignition. The guy i brought it of said that the tachometer has not worked since an auto electrtion installed a relay for the ingition to work. It appers that one of the white wires from the tacho goes into the relay box and if you unplug this the engine will not run.

I have tried swaping the tacho with another one to see if the tacho was stuffed but it still does not work.

There are three wires coming out the back of the tacho: two white and one brown. does anyone know what these wires should be conected to for the tacho to work?

And has anyone attached the the original tacho to an electronic ignition, if so could you explain how you did it?

or do i have to go for an aftermarket tacho?

any help would be greatly appreciated!

Re: tacho not working

I'm not familiar with Clubman gauges. From your post it sounds like it's part of the stock two gauge cluster. Is that right? Do you find the letters RVI or RVC on the face? If so, please post these back here. It SOUNDS like you have an RVI tachomter. I'd rather not speculate until you post back and confirm or dispel that.

What about the electronic ignition? Was it stock or added later? Why and where was the relay added?

The more information you can provide the more we'll be able to analyze the situation and hopefully help you.

Re: tacho not working

Thanks for the reply, the tacho is part of a three gauge cluster, the left gauge is the speedo, the center gauge is fuel and temp, and has smiths written on it and the tacho which is on the left, does not have RVI or RVC on the face it just has 12v neg earth and RPM X 100 and goes up to 80. This mini was made in australia by leyland so im not sure if these gauges would be diffrent to overseas models? The electronic ignition was added to the car, it has a bosch coil, and im not sure what brand the dizzy is it has been done by a local company called scorcher. I was told that the relay was need for the electronic ignition to work, but as i said before i purchased the car like that so im not sure of the exact resoning behind it. The location of the relay is inside the front guard near the coil.

Re: tacho not working

Without the RVI or RVC identification I can only make some suggestions.

Trace the wires to and from the coil. RVI tachs are wired in series with the coil power. Typically one white wire is connected between the tach and the ignition switch. A second white wire goes between the tach and the coil (+) terminal. There will also be connections to chassis ground and a switched +12V. Of course... there will also be some form of power to a lamp.

An RVC tach will have the same power and lighting connections as the RVI. However, the RVI does not run a white wire to the ignition switch. It has a single (usually white/black) wire going to coil (-).

RVI tachs typically do not operate properly (if at all) when electronic ignition upgrades are made. RVC tachs handle this much better.

Take a look at your wiring and post back what you find.

Re: tacho not working

It appears that one of the white wires goes to the igition switch, and the other one goes to the relay, which is connected to the coil.

Being in series would explain why the engine cuts out when you unplug the white wire from the relay. There is a brown wire which comes out the back of the instrument cluster behind the speedo and plugs in to the tach.

I don't have a test light here but a couple of days ago i was at a friends place and im pretty sure that it was a +12v, which does not leave a neg earth if that is the case.

The power to the tacho light is supplyed via a circut printed on thin plastic which covers the the back of the instrument cluster.

Assuming that it is an RVI gauge or simalar to an RVI gauge do you know of any online stores where i could get an RVC gauge or an after market gauge that i could fit into the plastic housing of the orginal gauge and that will work with electronic ignition?

Re: tacho not working

I'd feel better seeing a detailed sketch of the wiring with all the relay contacts identified. Lacking that I can only speculate.

It SOUNDS like the person who re-wired the car for the electronic ignition may have pulled a separate wire to power the coil itself, using power from the ignition switch to pull in the relay. (You turn the ignition on, this pulls in the relay, and when the relay closes it passes power to the coil and/or ignition module from some non-standard power connection).

The fact that you have two white wires connected to the tach makes me highly suspicious that it's an RVI instrument but frankly I thought these weren't used in BMC/BL cars after about 1969. I'd hate to advise you in any way that may damage anything.

In Lucas wiring, brown is "hot" power. Usually you see this for the wire from the solenoid to the fuse box and brown with colored traces to/from the alternator or generator control box depending on the age of the car. It sounds like you're installation has 12v to the instrument through that brown wire. The earth connection is probably on the circuit board.

The way the white wires are currently connected (if this is indeed an RVI tach) will not work. I'll write you a PM about this as I don't want to post information in this thread that may accidentally be used and cause damage to someone's car.