907
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| posted on 16/8/05 at 08:25 PM |
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Smiths Tacho wiring
Hi All,
The electrical dimwit is stuck again.
I have a smiths rev counter that has no markings to indicate what goes where.
All three are insulated from the case so I will need an earth on that to make the bulb light,
but A, B & C have me stumped.
A "pos", a "neg", & from neg side of the coil ?
Cheers for any help.
Paul G
 
Rescued attachment wiring1s.jpg
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johnjulie
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| posted on 16/8/05 at 10:09 PM |
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Looks like there should be a female plug to fit those spades. If you get the number off the front of the dial, or maybe the rear case,and contact
Speedy Cables, they will give you the details. (there are different types)
01639 732213 or 01639 732299
Or email them at
www.speedycables.co.uk
send them the picture
Cheers John
[Edited on 16/8/05 by johnjulie]
JFDI
"Just F*****G Do It"
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Ronin
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| posted on 17/8/05 at 08:39 PM |
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There are numerous different types of Smiths tachos, is it off an MG. Only the very last ones fitted had a neg feed from the coil. All previous ones
had a constant 12v supply (ie from battery) to one pin. The other 2 pins were connected to the +ve supply from the ignition to the coil, ie the +ve
supply for the coil went from the ignition switch to one pin on the tacho and then from another pin to the coil.
See here (clicky)
Seems strange but mine works beautifully.
[Edited on 17/8/05 by Ronin]
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907
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| posted on 17/8/05 at 11:42 PM |
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No numbers at all on the dial, no idea what it's off.
I'll post a pic tomorrow of the face.
Cheers, Paul G
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907
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| posted on 18/8/05 at 10:45 PM |
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Pic of Face
No numbers, just "neg earth"
Paul G
 
Rescued attachment tacho-face-s.jpg
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907
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| posted on 18/8/05 at 10:49 PM |
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Or I'v got this one
Trouble is, to do 7.5K I'll have to move the spider. 
Any ideas ?
Paul G
 
Rescued attachment MK-II-tina-s.jpg
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johnjulie
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| posted on 19/8/05 at 09:06 PM |
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The bottom one with the looped wire at the back is an IMPULSE TACHO, one side of the loop goes to the ignition switch, the other side goes to the
coil. You also need a live feed and earth to it. Not sure about the top one, looks in better condition. What Speedo are you using? Surely you want
matching gauges?
Cheers John
JFDI
"Just F*****G Do It"
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johnjulie
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| posted on 19/8/05 at 09:08 PM |
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I think you'll find very a small set of numbers on the bottom of the dial, where it says Made in the Uk.
Cheers John
JFDI
"Just F*****G Do It"
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907
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| posted on 19/8/05 at 11:00 PM |
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Hi John,
The pic in post 1 is the back of post 5.
As you can see it's in very good nick so I would prefer to use it if I can.
It has no numbers on it at all, just "Smiths" " made in UK"
The one in post 6 is from a MK II Tina and has the number "RV1 2413/00" by the N in GEN. (ignition light)
Most of the marks, including the dead spider  are on the inside of the glass, so I think it would clean up OK.
So to wire up I take the wire off the + side of the coil and join it to the white wire (male bullet ?)
and the other white (female bullet ?) to the + on the coil, effectively adding it into the ignition switch to coil line.
The spade on the left of the pic then has another live to it ? Then a - (earth) to the case.
All my gauges are Smiths white on black so they sort of match. ( see interior thread, "Finished my Dash" )
Many thanks for your help. I realy do get stuck on this sort of thing.
ATB
Paul G
[Edited on 19/8/05 by 907]
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rusty nuts
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| posted on 20/8/05 at 12:31 PM |
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Paul, I think the second tacho should be wired so that the loop is in the low tension side of the coil between the coil - neg terminal and the
distributor . This would only work with points (I think) The terminal on the left should be the ignition live +pos feed . Would have thought that
Speedy Cables might be able to help if you need to get one refurbished HTH
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907
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| posted on 21/8/05 at 09:15 AM |
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quote:
Originally posted by rusty nuts
Paul, I think the second tacho should be wired so that the loop is in the low tension side of the coil between the coil - neg terminal and the
distributor . This would only work with points (I think) The terminal on the left should be the ignition live +pos feed . Would have thought that
Speedy Cables might be able to help if you need to get one refurbished HTH
Hi Rusty,
I'll have a go today at wiring the rough one as you say.
I have a points dizzy off an MGB on the 907 so if I try this one first then I can clean it up if it works.
Cheers
Paul G
p.s. Time we had another pint.
If it works, I'm in the chair. 
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rusty nuts
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| posted on 21/8/05 at 10:40 AM |
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Look forward to it , see you soon , if the weathers OK may be in the Luego .
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907
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| posted on 21/8/05 at 08:31 PM |
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quote:
Originally posted by rusty nuts
Look forward to it , see you soon , if the weathers OK may be in the Luego .
That would be brilliant, love to see it.
I think that tacho's bu**ered. I'v failed again. 
But on the other hand......
the brake warning light worked, so did the fuel gauge, and the mods to the cooling system....
And I just had to take it up the road again... well, you can't test a tacho stationary can you ?
ATB
Paul G
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907
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| posted on 22/8/05 at 09:02 PM |
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YIPEEEEEEEE
Problem solved at last.
Took the tacho to a mate who does fuel injection work for local garages.
He put an amp gauge on all the terminals and detected a reading of
250 mAmps between B and C. No reading between AC or AB.
So A is signal from neg side of coil.
B is positive (feed)
C is negative (earth)
IT WORKS
Thanks for all your replies
Paul G
 
Rescued attachment wiring1s.jpg
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Ferg
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| posted on 24/8/05 at 08:25 PM |
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Well done Paul!!!
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kango
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| posted on 29/8/05 at 07:15 PM |
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How about helping me with this SMITHS rev counter. It is from a Jaguar.
The numbers on the face reads
RVC 2610/01AF
3 terminals on the back.
Spade terminal to the body (I take this as earth) And then a round terminal and another spade terminal insolated from the body.
 
Rescued attachment Rev Rear 2.JPG
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907
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| posted on 30/8/05 at 08:27 PM |
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Hi Kango,
Try it with a multi meter on the mili amps setting.
If it works the same as mine then you'll get a reading only between pos & neg.
You know which is earth (neg I take it) so one of the other two must be pos.
The one that dosn't give a reading is the signal from the dizzy side of the coil, I think???
Please bare in mind I don't know what I'm doing, I simply watched what my mate did.
I'll listen for the bang. 
Paul G
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johnjulie
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| posted on 30/8/05 at 09:23 PM |
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The Spade terminal goes to a live feed from the a fuse that is only live with the ignition on.
The Bullet connector is wired to the -ve side of the coil.
The Spade on the body of the Tacho goes to earth.
Standard Smiths Tacho wiring for -ve earth vehicles.
Cheers John
JFDI
"Just F*****G Do It"
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kango
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| posted on 31/8/05 at 04:28 AM |
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Thank you..
Clearly this is a 6 cylinder unit.
What do i do to get the calibration right.
It currently only goes to 5K.
So ... anybody tried changing the face to indicate the true revs?
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NS Dev
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| posted on 31/8/05 at 12:05 PM |
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I have one identical to the one with the spider in it and it is positive earth............just worth considering??? (they might have changed
internally but kept the outside the same perhaps??)
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kango
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| posted on 31/8/05 at 05:28 PM |
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It is printed "NEGATIVE EARTH" on the face. Thanks for the warning.
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