13 replies to this topic

[MGBailey007]

I need abit of help I have just got some new clocks for my sprite I have the normal clocks in there at the min (the made in japan ones) the smiths clocks I have got are about 30 years old, they are out a 1275 gt or a clubman I think and have a negative earth, my question is do I need a new speedo cable to get the mph working and how do you wire up a negative earth

Thanks, Matt

[Doz1971]

If the old clocks were made before 1984 it's unlikely the speedo will read correctly. The fitting is the same. Does the speedo read to 90MPH (Clubman) or 120MPH (1275GT) ?

Your car is negative earth, so you should have no problems there.

[MGBailey007]

They read 120mph and the rev counter doesn't work and the connections on the back are different

[wile e coyote]

caerbont is a useful resource - may help....

http://caigauge.com/qal.html

[dklawson]

Use the search feature on here to learn from old threads about matching the turns-per-mile out of the gearbox to a particular speedometer. There are many variables that affect whether a speedometer will be compatible with your car's gearing and tire size.

The other gauges are not simple plug and play. First, the later Smiths gauges (post 1960s) are not polarity sensitive so there is no worry there. They can be wired either way. HOWEVER, they are NOT powered directly by 12V. You MUST add a voltage stabilizer to the wiring to supply the gauges with a controlled 10V. You will find sources on eBay selling generic, solid-state voltage regulators/stabilizers for gauges. They will be suitable.

Apart from that warning, follow the wiring diagrams for the donor car you got the gauges from to install the new/old gauges in your car.

[MGBailey007]

Use the search feature on here to learn from old threads about matching the turns-per-mile out of the gearbox to a particular speedometer. There are many variables that affect whether a speedometer will be compatible with your car's gearing and tire size.

The other gauges are not simple plug and play. First, the later Smiths gauges (post 1960s) are not polarity sensitive so there is no worry there. They can be wired either way. HOWEVER, they are NOT powered directly by 12V. You MUST add a voltage stabilizer to the wiring to supply the gauges with a controlled 10V. You will find sources on eBay selling generic, solid-state voltage regulators/stabilizers for gauges. They will be suitable.

Apart from that warning, follow the wiring diagrams for the donor car you got the gauges from to install the new/old gauges in your car.

By Gauges do you mean oil pressure and water temp and stuff like that because I have volt stabilisers for them it's just the speedo not working but I need a new cable anyway so I wasn't sure what to get and the rev counter not working as the terminals on the back are different the fuel gauge has a volt regulator on the back of the clocks as standard

[dklawson]

If you have electric gauges (oil pressure and water temperature) you will need a voltage stabilizer for them. I have never seen a Mini that had an electric oil pressure gauge from the factory. Likewise, I have never seen a Mini with a factory installed mechanical water temperature gauge.

You said your car had the Nippon-Seiki gauges. Those do not have the voltage stabilizer where you can access it. The stabilizer is built into one of the two gauges but I don't remember which. I assume when you reference the stabilizer on the "back" you are talking about there being a voltage stabilizer on the back of your new/old Smiths donor gauges. If that is what you meant, then yes, you have the stabilizer you need for the new gauges.

There are different types of Smiths tachometers. Look on the gauge face for the letters RVI or RVC and let us know which you have. Also let us know if you have electronic ignition. Once we know the type of tachometer and your ignition type we can discuss tachometer wiring.

Early Smiths speedometers had a male thread on the back for an M12x1 nut on the end of the cable. Sometime in the early to mid 1970s Smiths appears to have changed to a clip-on cable type. The gearbox end of the speedo cables is the same and threaded 3/4-26. If you are planning on using an early speedo in a later car you need to buy the early speedometer cable to match. All that is moot if your turns-per-mile number on the new speedometer do not match what is right for your car's gearing and tire size. Yes, you can have the speedometer re-calibrated/rebuilt to match your car's gearing but it is expensive and finding the "right" speedometer is likely to be more cost effective.

[MGBailey007]

I have electronic ignition and on the gauges it says RVI 2435/00A

[dklawson]

That is what I was afraid of.

RVI tachs seldom work with electronic ignitions. They are an older design wired in series with current flowing to/through the ignition coil and they monitor current pulses. You will be much happier in the long run looking for a later Smiths RVC type tach instead. RVC tachs are more or less similar to modern tachometers. They use a single sense wire connection to coil (-) and they "count" voltage pulses. Those are compatible with electronic ignitions.

[MGBailey007]

So I'm better off buying the newer smiths clocks and the speedo will plug in and the rev counter

[Doz1971]

Don't dispair. My RVI Tacho works fine on my Metro electronic ignition. You'll need to connect the two sense wires in series with the 12 volt feed to your coil. Don't put it between the coil and the module, as I found it rarely read correctly.

[dklawson]

By all means try the RVI tach. However, if and when you find it doesn't work, do not spend money on "fixing it" to work with your electronic ignition.

Doz, congratulations. You are the second person I know of who has found an RVI that works with electronic ignitions.

[Doz1971]

It's only a current transformer, so there's no reason it shouldn't work, I might have just got lucky. I suspect there was too much ringing on the signal between the coil and the "points" for it to work properly. It's just counting gobs of current at the end of the day.

[dklawson]

You are indeed lucky. I am not an electrical engineer but I have the following understanding of the problem. Points distributors have a certain dwell period that controls the on/off flow of the current. Electronic ignitions have a different but functionally equivalent on/off time. The difference in the on/off time affects the accuracy of the RVI tachometer. I know it seems like it shouldn't but there is a lot of anecdotal evidence that the RVI tachs don't (typically) work with electronic ignitions. I purposely bought an RVI tach from an MG just to experiment with and found that while it did work with points, no amount of tweaking or wiring changes allowed it to work with an ignitor module.