How to convert a V6 tacho to suit a V8

[Bilbs]

Or the other way around

OK, i have seen a few threads on asking how to do this, and with the popularity of the L2 to L3 dash conversions, i figured it would be usefull for people to know how to convert their tach to save to cost of hunting the rarer, V8 L3 Cluster.

The basic tools you will need to do this if the cluster is in the car are as follows.

No2 Phillips Heads Screwdriver
Flat Blade Screwdriver
Small Flatblade screwdriver (Jewelers Type)
Soldering Iron (Or if your american, a Soddering Iron lol)
Solder
Pair of pliers
Clean work area
A Cold can
About an hour of your weekend


First things first, is to remove the cluster from the car, if you already have it out, you get to skip the step, so you can have a drink while you wait for the rest of us to catch up to ya

Start by unscrewing 2 phillips head screws in the top of the dash surround, then tilt the steering wheel to its lowest posistion
Grasp the buttom of the surrond, and jerk/pull it towards you, this should release it from the clips and it will pull out, reach behind and unplug any switches, but take not of which plug goes to which switch, i happen to know the th ac plug will plug into the hazard switch lol
Drop the fuse panel cover down, use the flat blade to undo the clips that hold it up, now on the RH side of the cluster from underneath you will fell a connector, unclip this from the cluster
Now there are 2 scres that hold the cluster to the dash, remove these and the cluster will slide out towards you.

Well done, now you may have a mouthfull of your can if you like, and take the cluster to your work area (dont forget to take your can with you, dont want it getting hot in the car :P)

Anyone who skipped the first step can pickup with the rest of us here

There are 3 small screws in the bottom of the cluster at the front that look like a cross between flat and torx, just use a flat and remove these, you can then unclip the front of the cluster and put it out of the way, next there may be a black surround left in there, remove this as well, and place it aside.
Now there will be 3 small nuts on the back of the cluster that holde the tacho in, use the pliers to remove these and the tacho will come out of the cluster.

Now to remove the face of the tacho, grasp the needle in the center, and gently twist in anticlockwise againts its stop while gently pulling up at the same time, this will remove the needle, take note of where it pointed before you take it off, take not at what angle you were looking at it while it was pointing there, you will need to remember these for putting it back together.
Remove the 2 tiny black screws that hold the face on, now the face and light diffuser will both come off, and there you have it, your V6 tach waiting to be modded

Now you will nitice some resistors on the PCB of the tacho, R1, R2, R3, R4 and R5. R1 remains unchanged, on your V6 unit R3 and R4 are blank, and R2 and R5 have a resistor in them. You need to take the resistor out of R2, and put it into R3, then move the resistor from R5 to R4, and last you will put a 220K ohm resistor into R2, if you dont wanna be bothered to buy one, you could rat this outta your old V8 tacho, level 2 or 3, it will be the same value.

Now just reverse the dissasebaly precedure and you have a Working V8 Tach
This is how i did mine about 6 months ago, and it works perfectly.

I have atached a pic of each tach for your reference, and if you are going lev 2 to lev 3, dont worry, they still go to the same values, even though they look like they are in a different spot, if you trace the busses on the back of the board, they are wired identical, just on a diff shaped pcb, so hope this helps ya out, and ahh, dont forget the scales

[centy]

ok dumb question but i recently scored a dash with a production date stamp of 12/ 96 and it only has 3 resistor spots
r1 red blue brown gold
r2 red brown black yellow
r3 red red yelolow gold
any ideas?

[Bilbs]

These 2 images show the differences, the L2 tachs are the same, although they do look different, they are not, just a different layout, due to a diff shaped PCB

[jimmig81]

This is cool mate converted vn to an 8 an im gonna convert a vs to an 8 so thanks

[echnidna]

Stupid question but could you reconfigure the tach to work on a 4 cylinder by changing resistor vales?

[Bilbs]

i cant see why not, i wouldnt have a clue on what to change, i imagine ya might use the V8 link posistion, then half the resistance of r3 maybee, just a guess, try it at your own risk, if ya fry ta tach, or ignition dont blame me

[pow3rslave]

hey man, great thread, there's just one thing i'm not clear on.

• You need to take the resistor out of R2, and put it into R3
• move the resistor from R5 to R4
• last you will put a 220K ohm resistor into R2, if you dont wanna be bothered to buy one, you could rat this outta your old V8 tacho, level 2 or 3, it will be the same value.

i've done most of this. i moved r2 to r3, and r5 to r4. but looking at the original resistor in r2 (now in r3) it's red, red yellow, which makes it 220k +-5% anyway.
also just wanted to check your new r2 value of 220k ohms was right because the one in your v8 pic seems to have different bands (hard to tell tho)
resistor code calculator

[Brett]

Is it possible to just swap the whole tacho units around?

Say you have a V8 level 3 cluster with high kms and V6 level cluster with low kms, could you pull the tacho unit out of the V8 one and put it in the V6 one?

[SMG_07]

Is it possible to just swap the whole tacho units around?

Say you have a V8 level 3 cluster with high kms and V6 level cluster with low kms, could you pull the tacho unit out of the V8 one and put it in the V6 one?

same Q
really want 2 know!

[SMG_07]

Aheeeeeem...
Still really what to know man !

[88GreenVN]

Aheeeeeem...
Still really what to know man !

You can use a V8 tacho in a V6 cluster not problem - done it my self before.

The temp gauge is a little different - but not enough to worry about.

The temp and tacho are the only differences between V6 and V8 clusters.

[SMG_07]

THANK MAN

next in the to do list ... tacho conversion

[88GreenVN]

hey man, great thread, there's just one thing i'm not clear on.



i've done most of this. i moved r2 to r3, and r5 to r4. but looking at the original resistor in r2 (now in r3) it's red, red yellow, which makes it 220k +-5% anyway.
also just wanted to check your new r2 value of 220k ohms was right because the one in your v8 pic seems to have different bands (hard to tell tho)
resistor code calculator

I'll have to inspect a V8 tacho when I get home using the above resistor code calculator.

Also will it make any difference as to which way around the resistor goes into the PCB?

[88GreenVN]

OK just got my lad to look up the items I purchased 2 weeks ago and he reports red red brown brown on the resistor and the docket said 200k .25w r r brn br.

On the risistor code thingo it only has gold, silver or none for the last band. So no wonder it failed to work.

What is the .25 w about?

[88GreenVN]

Here is a link to photos of a V8 tacho resistor needed to convert the V6 to a V8 tacho.

VR/VS V8 tacho resistor pics

The risistor code is red red yellow brown. (from DSE) 6 cents each.

[88GreenVN]

Converted 3 more v6 tachos to v8 tonight and all 3 worked. So the red red yellow brown is the go.

RIP 4 tacho's that I killed by putting 220 resistors (should have been 220k) in the tacho in error.

[D3CID3R]

Resistors come with a tolerence rating. Manufacture can't garruntee that all there 220k. Hence a tolerence rating. + Or - %

[Tsunamix]

Heres an easier way -

Go to holden and have them change the dash cluster program using a tech 2 tool. $44.00

VT series 2 on, the BCM supports both 6, 8 and 8 High voltage cylinder configs for the tacho

[88GreenVN]

Heres an easier way -

Go to holden and have them change the dash cluster program using a tech 2 tool. $44.00

VT series 2 on, the BCM supports both 6, 8 and 8 High voltage cylinder configs for the tacho

Yep for a VT, Holdens are the go. For a VN to VS - changing the resistors is cheapest way - $0.06 for the risistor

[savage1987]

Thread dig:

anyone had any success switching a tacho to 4cylinder mode? A method was suggested above but nobody says they've tried it.

[Bilbs]

i never bothered to check the value, just pulled it outta me old one, but now wish id modded the temp guage, it is a fair way diff, my guage never gets over a needle under 1/4, where it should sit just uner half, so if it gets to half way between 1/4 and half id be worried as i have no idea how hot it is then, only time i saw it come above a 1/4 tho wasd balck sat when a/c was goin full and i was fair hammerin to get to party in time lol