Spitfire Help wiring up a tach

[Darwin]

Been a while since I have been around. Switched the spit over to an Advanced Distributor Lucas model. In doing so I lost the mechanical tach drive that the Delco provided. I have purchased a Smith's JVC 2414/01f tach off ebay. I haven't a clue how to wire it. Can anyone explain it to me? There are 2 spade connectors and a round pin on the back side. One of the spade connectors is obviously ground but the other two I haven't go a clue about. Help!!!!

 

[Mickey Richaud]

Hey, Dar -

Those other two would be power and signal (from the distributor/coil wire most likely). Hopefully, someone with direct knowledge will chime in soon with specifics.

Here's a diagram:

https://www.triumphspitfire.com/images/wiring/75diagram.jpg

Mickey

 

[Rhodyspit75]

Here's a shot of my tach in a 75. Match this with the above diagram and you should be fine. No ground connection on any of the spade connections.

 

[dklawson]

I assume you meant Smiths "RVC".

RVC tachs are voltage pulse sensing. On the back of the tach should be a little brown circuit board with a male spade lug and a bullet connector. Some (but not all) tachs also have a male spade spot-welded directly to the gauge case. The gauge case must be grounded either using a ground wire with ring terminal on one of the threaded tach mounting studs OR connected to the male spade lug spot welded to the gauge case (if such a spade lug exists). Switched, fused 12V is supplied to the male spade lug on the small circuit board. A sense wire is then connected between the bullet connector and the coil (-) terminal.

Since you have converted to the Lucas dizzy, it would be nice if you also used normal Lucas color coded wire (available from britishwiring.com and others). In Lucas color schemes, "dark green" is used for fused, switched circuits, "black" is common for grounds, and white/black is used for coil to distributor and coil to electric tach wiring.

 

[DNK]

Doug- Dan Masters used Y/W as the Tach sensor wire.

 

[dklawson]

I won't argue against Dan but white/black was used on cars where RVC tachs were standard or a factory option. I think the later Spitfires used white/grey for the sense wire to coil (-)... close enough for most to see it as faded white/black.

EDIT: Don, thinking about this more, I suspect the yellow/white you mention was/is really white/yellow and not associated with the tach. On cars with ballast ignition systems the 4th solenoid terminal is connected to coil (+) using white/yellow and that is a bypass wire supplying the coil with full power during starting. The tach sense wire connects to the other side (coil -) so using any white/yellow or yellow/white for the tach would be very confusing on cars with ballast ignition systems.

 

[Darwin]

Thanks all. Now I just have to get under the dash and hook things up. Not as easy as it used to be a few decades ago for some reason.

 

[DNK]

Doug- I might be talking apples to oranges here...
The wiring panel he sold has the
Yellow/ White -Tach connection in the manual
...but, this was for the TR6 so YRMV

 

[dklawson]

Weren't factory tachs in TR6s cable driven like the one in my GT6?

 

[Rhodyspit75]

The color is actually white/slate if you feel the need to be correct. You could also use white and drag a Magic Marker down it to add a stripe.

Its not real hard to drop the dash center section and gain access to the tach. I think it is easier then doing it from below.