11 replies to this topic

[sweetser]

Model: mayfair
Year: 1989

I recently brought myself a new rev counter after i couldnt get the old one to work



Now this is were i need you clever peoples help i dont have the foggyest how to wire it in!





Now im guessing the black is my earth?? and also were do the rest go??

And i also got told i ''may'' have to change my coil to a non-ballast one, is this correct?

Thanks in advance Luke.

[il-barba]

http://www.theminifo...p;hl=tachometer

a search would usually help

[sweetser]

Thanks for that

Ill post it here aswell so i can find it easyer lol



this is what i got (thanks to tom )

red is fused 12v feed
Black is earth
ANd obviously the bulb holder is for a bulb haha (side lights lol)

But, im confused as to were i put the white wire. What side of the coil do i put it to?? + or - as i dont know what CB stands for... and also were abouts does the white wire go on the distrubutor and what does the dotted black line mean going from the dizzy to the coil?

And that drawing dont say if i need a balast or non-ballast coil??

And lastly probly a stupid question but were can i get the wire from to extend/renew all the old wires?

Thanks Luke.

[sweetser]

Bump, help please

[dklawson]

You have a Smiths RVI tachometer. There is not a "single" white wire to hook up, there are two (2), one from each side of the loop. Succinctly, power to the coil flows THROUGH the white wire.

Start by connecting an earth to the gauge and supplying it with switched +12V as shown in the diagrams above. Since you do not have this type of tachometer now, the easiest method of connecting it will be to pull two white wires into the engine compartment. Run the white wires to the distributor. On cars with points there will be a white/black wire running between the distributor and the coil. Completely remove that wire but note exactly where each end was connected. Connect one white wire where the white/black was removed from the coil, connect the other white wire to the distributor. Inside the car, splice one white wire to each end of the loop on the back of the tach. Start the engine. If the tach reads "funny", switch the two connections (coil/dizzy) in the engine compartment.

Here's a "Readers Digest" condensed explanation. Each time the points open they interrupt current flowing through the coil. The white tach wire carries the current to/from the coil to the points. Each time the points open and close, an electromagnetic pulse is created in that loop of wire on the back of the tach. Inside the tach is basically a coupling transformer which creates and internal pulse based on what it senses in the loop of white wire. The circuit inside the tach uses these pulses to operate the needle movement.

It does not matter whether you have a standard or ballast ignition. This tach (and most tachs) will work with either. What IS important is do you have an electronic ignition? IF you have an electronic ignition, do NOT expect this type of tach to work properly. Sell it and buy a Smiths RVC type or another brand of voltage sensing tach. The RVI tachs do not like electronic ignitions.

And for the record, CB and SW stand for Contact Breaker and (ignition) SWitch. However, I've always thought the sketch you posted was VERY misleading. EARLY coils were marked CB and SW and they were for POSITIVE earth cars. On later cars or cars that have been converted to NEGATIVE earth, the connections may be marked differently OR if an early car is fitted in a negative earth installation... CB goes to the ignition switch and SW goes to the coil. Don't be confused by this. Your car is likely to have a later coil without these markings. Do note however, that in the sketch they show a dashed line between the distributor and CB terminal. THAT is the white/black wire I said to remove.... which is why they show it dashed.

[sweetser]

Thanks mate thats a great help

[mk3 Cooper S]

Thanks for that

Ill post it here aswell so i can find it easyer lol



this is what i got (thanks to tom )

red is fused 12v feed
Black is earth
ANd obviously the bulb holder is for a bulb haha (side lights lol)

But, im confused as to were i put the white wire. What side of the coil do i put it to?? + or - as i dont know what CB stands for... and also were abouts does the white wire go on the distrubutor and what does the dotted black line mean going from the dizzy to the coil?

And that drawing dont say if i need a balast or non-ballast coil??

And lastly probly a stupid question but were can i get the wire from to extend/renew all the old wires?

Thanks Luke.

Wouldn't happen to have one of those diagrams for a Jagar Tacho have you?

[sweetser]

Nope mate im sorry i dont i got it from il-barba's link lol

[dklawson]

Mk3, you could always post a picture of the front and back of the Jag tach. I'm confident we'd be able to help you sort it out. However... what will you put the Jag tach into (probably being a 6- (or 12-) cylinder instrument)?

[cheesebadger]

Great help, cheers! I was going to put up the same question in a few days. Good explanation!!!

[alexangas]

fantastic help! Cheers guys! Ill try fit mine now as well

[dklawson]

Wow !!!  You did a good job of using the search feature to find that old thread !