Tacho

[Griff_Sle]

Hey guys, i have a vh sle with a 253 and the tacho is reading incorrect. I have been told that they have a switch on the back of the tacho to change them from 4,6 and 8 cylinders, i have not been able to locate this switch!
Does anyone have any info on what might be causing this problem.
Cheers...

[NOT.BT1]

sounds like its not conected properly to me is it the factory tacho or after market id check the wiring out to make sure its all conected up properly and go from there

[Griff_Sle]

It is the factory tacho... Wiring setup appears to be fine.

[immortality]

doesn't it trigger from the coil, check the connection there also

[Griff_Sle]

Connection at coil is fine, thats why i cant understand why the tacho wont read correctly...

[Pub247]

If its a factory setup the signal does not run from the coil directly there's a twin plug behind the cluster which the oil pressure and tacho signal wires run from the cluster to. Now because mine is not standard i run a wire directly to the coil. If you want (bit of a mission) you can try running the wire directly from from the clust to your negative side of the coil and see if that works. Sort of an isolation test if you will. This will tell whether its the wiring or the tacho itself

[Pub247]

Sorry Griff didnt read the whole thread correctly, You said it does not read correctly? is it the original cluster it might be a 6 cylinder one therefor the rev count will be out

[Griff_Sle]

I tested resistance at that plug behind the cluster to the wire at the coil and there was no resistance, so there is no break in the wire anywhere.
It is the original cluster, although my theory is that a while back before i had the know how to do it myself, i sent it to a holden dealership to get some of the globes in the cluster replaced. Someone at the dealership might have had a vh with an 8 and needed my tacho, so they could have easily swapped it, because it started happening as soon as i got it back from them...
Was there a different tacho unit for each sized motor? If so then that might prove my theory...

[Pub247]

I've have also been told there's a switch to adjust it. Also i've had 2 clusters one a v8 (which read wrong in my 6 ) and the other a 6 i've compared them and they're both the same the only thing different was the position of the screw at the back of the tacho one was a quarter turn in different from the other. now i'm not sure if this is what adjust them though. Now i cant see holden getting vdo to make 3 different for each engine combination so i assume they're adjsutable to suit the application.
Griff it is possible someone swapped them on you, They'd only have to swap the speedometers over and it would be hard to tell. Is there a wire running straight from the cluster to the coil? I cant understand why it'd be like that in a sle when the original harness is there. Can you give me more info on the problem? i.e. do the revs read slower than normal or faster?

[Griff_Sle]

Slower than normal...

[Pub247]

Ok i'll mess around with mine tomorrow i'm doing work on my car anyway so i'll have look into it. I wouldn't mind knowing myself if they're adjustable

[Griff_Sle]

Cheers... I'm looking forward to hearing how you went!

[vkberlina]

I would first check all connections, including the plugs on the coil someone may have connected wires up tot he coil incorrectly, or something may be earthing out funny, condenser may be faulty or incorrect. If all is ok your tacho may have been switched.

From memory the factory tachos are adjusted by a pot inside the tacho not but a switch like after market ones.

If you have a digital tacho you can use or borrow, pull out your cluster and remove the tacho from the cluster and locate the adjustment pot make small changes at a time and check its calibration.

Previously I have had mine adjusted by an instrument guy who has calibrated all my guages individually at once.

cheers
scott

[Griff_Sle]

Can you tell me how you would adjust the tacho, ie. Which way to turn it and how many turns?

[vkberlina]

sorry no info on which way to turn it etc, mark the original positions. I suggest you do small changes making note of what you change you should quickly work out which way it needs to be changed and how much needs to be adjusted.

cheers
Scott

[Pub247]

Interesting scott i'll have a look at it give it a test on mine i dont mind if i screw it only cost me $20 i'll just buy another