Tacho issues

[Aussiexs11]

Paul, and all,
Well I have checked connections, and whilst at it took the time to do the basic maintenance like check battery levels, change air filter for a K&N unit (and thats a damn good thing to do- why hadnt I done that years ago??), but anyway, I checked wiring and all remakably good, tidy and together, no corrosion, no loose wires etc. must have put it all back together years ago properly, so i am happy with that.
I then swapped out the tacho for the unit I got from paul, and I received a double surprise. The tacho indicated as it should and the fuel sensor even worked!
So I took it out for a leisurely test run around the local hills (Jenolan rd, McKanes falls rd etc) and attemted to see how the engine revs recorded, and I was correct, the noise I had been hearing from the engine was a rather lot of RPM's , the "new 35 year old" tacho was indicating. There is life above 6000rpm after all!
So thank you Paul, and thanks to all who commented. I now have the other unit as an emergency spare if anyone needs it, it just doesnt like to swing too far past 5000 in any hurry at all! (and its fuel sensor works too).
Wonder what the next issue will be....
regards
Grant

[hen]

That's an interesting problem you are having, Grant. Most of the issues with the tachos has been with the needle fluctuating and bouncing at certain points of the rev range. A lot of those dramas were cured by checking the alternator wiring connector behind the fuse box bracket as these are prone to the contacts corroding and in some cases the outer plastic housing melting. The tacho picks its signal up from these wires, so maybe a check and a clean of that connector plug and any others downstream of it just to eliminate them from the equation, then we can progress from there.

You guys are just full of it ,, Great information Thank You

[Jonesy]

Hey Grant
Have you fitted the tacho yet? is it a good'n or a dud?

[Eveready1100]

That's an interesting problem you are having, Grant. Most of the issues with the tachos has been with the needle fluctuating and bouncing at certain points of the rev range. A lot of those dramas were cured by checking the alternator wiring connector behind the fuse box bracket as these are prone to the contacts corroding and in some cases the outer plastic housing melting. The tacho picks its signal up from these wires, so maybe a check and a clean of that connector plug and any others downstream of it just to eliminate them from the equation, then we can progress from there.

[Jonesy]

Grant I found a tacho you can have.....condition unknown but you can try it if you want.

[Aussiexs11]

Well, A question for the group, cause I am sure someone has an answer.
I was discussing this briefly with Jonesy the other night and he thinks there has been a discussion on this before.

My 78 2H9 runs well, and I am prone to use the revolutions the engine willfully provides, but it seems that the tacho doesnt like to tell me just how hard I am pushing it.
It seems to indicate openly and freely till about 4500 rpm, then, as the engine starts to really wind up, the tacho just seems to very slowly climb. I think there is a slight issue with the tach.
Now, its electronic, so I am wondering if there is something I shoudl be looking at, or is it just a shagged old unit and worn out? 
Anyone had this issue?
Any advice, or, anyone got a spare tach. I did get another one, but it unfortunately bounces around so wildly I cant really believe it at all.
Lets see what the combined minds can provide.... 
regards
Grant