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MG MGB Technical - Tacho differences

What are the differences between the tacho’s please.

I appreciate that that RVI is current and RVC is voltage but is it possible to swap between RVI’s.

Is there ant difference between RVI 1433 and RVI 2430 except for dial details?

Regards

Dave
D M Tetlow

A 1433 was for North America from 68 to 71 and so was 80mm instead of the earlier 4" 2430 which continued through to 1972 for other markets including UK.

There was a change in the 2430 type from external pickup to internal, about the time the cars changed from positive earth to negative, I believe, and there was a suffix number change accordingly. Originally there was a continuous loop of white wire coming out of and going back into the main harness behind the dash and this had to be fed through the external pickup in a particular way, and reversed if the polarity of the car was changed. With the internal pickup there were male and female bullets on the back of the tach case, and corresponding connectors on two separate wires coming out of the main harness, so they could not be mixed up.

You can fit an early type to a later car by joining the ends of the two wires together, then it is just a matter of experimenting which way the wire is fed through the pickup. If fitting a later tach to an earlier car you will have to cut the loop of white, solder bullets to the ends, then experiment again as to which wire needs a bullet connector to fit onto the male on the case, and which doesn't and goes into the female.
Paul Hunt

Thanks Paul

I am trying to get a RVI 2430/00 replacement for a friend. I have now found a RVC 2415/00AF in my loft. I believe it looks the same as the RVI 2430 but would it work?

Dave
D M Tetlow

Dave I am looking to swap a RV! for the later type as my tach wont work with my MSD ignition. Pity its so far away but if all else fails:
Denis4

Dennis, Not to hijack this thread but when I encountered this problem, I bought an Autometer tach for $40 US. I then took a spare Smiths tach and swapped out the internals. It works perfectly! RAY
RAY

Ray Thanks for chipping in, you told me that once before and I had forgotten who, and which tach. I fitted a MSD tach adaptor with a diode and it worked great for a while but gone on the blink again.
Please tell me the model tach again.
Denis4

2415 was the UK voltage triggered used from 73 to 77 so should be fine, that is often the way people with RVI tachs have to go when fitting electronic ignition. You have to make sure the two whites that go through the pickup on the old tach and joined together, then run a wire from the white/black on the coil -ve to the pickup terminal on the back of the tach.
Paul Hunt

Thanks Paul
Denis4

This thread was discussed between 20/02/2009 and 21/02/2009

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