Tachometer

[JonPiz]

Im having an issue getting my tachometer to work. I have run a live from position 2 on the ignition swith to give a live feed to the gauge. I have also run a wire from position 2 that loops through the signal block on the back of the tacho and connects to the positive side of the coil. Still nothing happens. Ive tried two tachos but neither work

 

[hartmandm]

Did you verify ground?
Did you check you have 12V on the connection from the ignition switch to the tach?
Do you have the induction block?
Did you get the coil loop correct? Maybe try adding another loop.

Mike

 

[JonPiz]

re

Did you verify ground?
Did you check you have 12V on the connection from the ignition switch to the tach?
Do you have the induction block?
Did you get the coil loop correct? Maybe try adding another loop.

Mike

Thanks for the reply, the first three points are sorted. When you say did I get the loop correct, what do you mean?

 

[Tom H]

Jon, You don't say in this thread, but i think you have an SII, so the tach you have in there is not original. Couple questions:

1) Is the tach you have in there built or modified to match your car's polarity
2) is you car Pos or Neg earth now?
3) Does the loop pass thru the rear signal block in the correct direction for the polarity of your car?
4) Do you have the steel U-clip across the loop, or do you just have the plastic piece?
5) If you have the steel u-clip in place, are both tips of that clip in contact with the mating tips sticking out from inside?
6) you can tell if you have a good ground if the lamp inside lights up.

Note that Mike's picture shows the U-Clip, but I cannot tell from his picture what direction the loop goes.

Tom

 

[JonPiz]

re

Jon, You don't say in this thread, but i think you have an SII, so the tach you have in there is not original. Couple questions:

1) Is the tach you have in there built or modified to match your car's polarity
2) is you car Pos or Neg earth now?
3) Does the loop pass thru the rear signal block in the correct direction for the polarity of your car?
4) Do you have the steel U-clip across the loop, or do you just have the plastic piece?
5) If you have the steel u-clip in place, are both tips of that clip in contact with the mating tips sticking out from inside?
6) you can tell if you have a good ground if the lamp inside lights up.

Note that Mike's picture shows the U-Clip, but I cannot tell from his picture what direction the loop goes.

Tom

the car is now negative earth and the tacho is as well. Everything is in place as you said and the earth is good. The only uncertainty I have is about the direction of the wire. How should it be for negative earth?

 

[JonPiz]

re

did a bit of digging and doh, you mean just change the direction of the loop as the current goes in the opposite direction on negative earth. Ill try that tomorrow as its dark now and I need a glass of wine!

 

[hartmandm]

Note that Mike's picture shows the U-Clip, but I cannot tell from his picture what direction the loop goes.

Admittedly, I don't know which wire end in the loop is going to the coil versus the switch. I never noticed any markings on the wire.

Mike

 

[Tom H]

Jon,

Couple more thoughts:

1) the tach could be defective
2) Hard to tell (or describe) which direction the loop should be , but easy to try reversing the loop ) or swapping the ends.
3) MAYBE the real issue - since this tach has been added to an older Apline- is that the original wire to the coil is still in place. Understand that for the tach to sense the pulses of current going to the coil, ALL the current to the coil MUST go thru the loop. Most likely the original wiring to the coil is still in place, and when you added the tach you added an additional wire - that goes thru the loop- and then to the coil. That means that approximately half the coil current goes thru the original path and half goes thru the tach loop- not enough to trigger the tach. If so, you need to disconnect that original wire to the coil, so that ONLY the wire looping thru the tach goes to the coil.

I'm guessing that this is the problem!

Tom

 

[JonPiz]

re

Jon,

Couple more thoughts:

1) the tach could be defective
2) Hard to tell (or describe) which direction the loop should be , but easy to try reversing the loop ) or swapping the ends.
3) MAYBE the real issue - since this tach has been added to an older Apline- is that the original wire to the coil is still in place. Understand that for the tach to sense the pulses of current going to the coil, ALL the current to the coil MUST go thru the loop. Most likely the original wiring to the coil is still in place, and when you added the tach you added an additional wire - that goes thru the loop- and then to the coil. That means that approximately half the coil current goes thru the original path and half goes thru the tach loop- not enough to trigger the tach. If so, you need to disconnect that original wire to the coil, so that ONLY the wire looping thru the tach goes to the coil.

I'm guessing that this is the problem!

Tom

The wiring loom is brand new and meant for an electronic tacho. Its either defective tacho or wiring loop issue. Im in my garage later so Ill give you some feedback then

 

[mikephillips]

Reverse the loop and try. The manuals don't really say and I don't know why it would matter but when I first put the new wiring in my Tiger the NOS tach didn't work. Reversed the loop, with no other changes, and it was fine.

 

[JonPiz]

re

Well I got allowed to go in my garage today by the good wife. I un-soldered the wire, reversed the direction and hey presto it worked!

Thanks for everyones input, sometimes its something so simple that solves the problem. Now to find out why the fuel gauge isnt working

 

[Tom H]

Great news, Jon.

Regarding the fuel gauge, I assume they're original SII Gauges. If so you will see battery power applied to terminal B (hard to see the letters stamped on the back of the case) . The other terminal is labelled T (for Tank). If you ground that T terminal, while ignition is ON, the gauge should go to full scale (Full). If it doesn't then there is likely no power applied or the gauge is defective. If the short causes full scale, but it fails to respond to the sender, the sender probably has a bad ground where the float lever pivots. See this thread for one solution:
http://www.sunbeamalpine.org/forum/showthread.php?t=23707

And see post #29 on this thread for a picture:
http://www.sunbeamalpine.org/forum/showthread.php?t=15723

Tom

 

[hartmandm]

For future reference, here is a diagram from the SAOC's The Alpine Guide showing the tachometer loop for a negative earth car.

Mike