S4 Sprint Tachometer hookup

[holywood3645]

I am replacing the wiring harness in my S4 and have a question on the hook up ot the pulse wire from ignition swith to the coil. The lotus diagram illustrates it as a loop (white wire) however the tach has 3 terminals on the right side. See picture.
My old harness , in picture, was modified and one wire is green (should be white)

Another thing, my voltage stabilizer was mounted on the Speedo. is this normal on the S4\Sprint?


I'm confused as how the sensing wire (white wire) should be connected as it is not the conventional loop... is there a wire that goes to the coil (from a different terminal?)

Does anyone know who this is supposed to be connected

Any pics or diagram that can help on the site

Thanks

James

[ardee_selby]

I think this thread was asking the same question. No pics/diagrams, but see responses.

elan-f15/elan-sprint-rev-counter-problem-t879.html

HIH. Good Luck

[oldelanman]

Hi James,

Assuming you are referring to the group of three connections arrowed......the male and female bullet connectors are for the signal wire -normally white - (the sensing loop is inside the tacho body) This is the wire from ignition switch to coil via the anti-theft switch in the glove box (if it's still fitted) as shown on the wiring diagram. The spade connector is the power supply wire - normally green.

More info here....elan-f15/tacho-connections-t18457.html

The voltage stabiliser is mounted on the speedo not on the tacho as shown in the workshop manual.

Regards,

[bob_rich]

Hi James

I have attached a sketch on how I think the tacho connections should should go
With some electronic ignitions modules the tacho's sometimes play up and I think that, provided the tacho is in reasonable condition it probably depends on whether the chosen ignition modules incorporates the equivalent of a points capacitor (condenser).

anyway hope this helps best of luck

Bob

[oldelanman]

Bob,
Any reason why you show the tacho after the coil in your wiring sketch ?

Regards,

[ardee_selby]

FWIW...

elan-f15/tachometers-aka-rev-counters-t23780.html

[holywood3645]

Roger gets the gold star on this one? after spending hours going though the books, this is exactly what I came up with. I thank you all for your input and interest.

James

[bob_rich]

Hi Roger and others.

The tacho's of the RV1 are current triggered and it could be wired in series with the coil at the SW end. This is in fact how the +2 wires it. The only thing to watch is that sometimes other connections are taken from the SW terminal, perhaps they should not be and these should NOT go through the Tacho. provided it is only the coil current then it should be OK either way. By using the CB connection this generally has no other accessories on it.

Hope this helps

cheers

Bob

[oldelanman]

Hi Bob,
Thanks for the explanation.
The reason I asked is that wiring the tacho from the CB side of the coil (assuming the coil is located in the engine bay) would need two extra runs of cable between dash and engine bay - from CB terminal to tacho and tacho back to distributor. Perhaps that's why it's generally on the SW side of the coil to minimise cable runs - and also save weight of course
Regards,