ALFAGTV6.COM

Steve R · Post by **Steve R** » Wed Nov 09, 2005 2:22 am

Here's two alternatives to get a GTV6 speedo working and reading correctly.

First option works for a transplanted 75 transaxle and sensor, I used the Dakota SGI-5 unit, which has a variety of settings to run pretty much any type of speedo on the market. If you use one set it up like this:

Only 4 wires are attached to the SGI-5: 12v Power, ground, signal in and signal out.

On my GTV6 the loom from the speedo provides ignition switched 12v on the pink wire and the signal return to the speedo is via the red/white stripped wire. I sited the SGI-5 under the rear seat near where the cables go through the floor and just screwed it to the upright area of metal. With the seat base pulled up I can reach the unit from the drivers seat - this is important for calibration !

The SGI-5 has 4 separate output terminal options. To run a stock GTV6 speedo the signal out is taken from terminal labelled "OUT1". The angled photo of the unit in situ is deceptive, the wire definately comes from "out1" not number "out2" !

There are 4 dip switches, set switch 1 labelled "#1 input type" to "on" and the other 3 "off". The speedo will now work, but likely read wrong, maybe wildly wrong!

To adjust the reading SGI-5 has coarse and fine tuning, I didn't bother with the coarse tuning, just used the fine option:

To the right of the dip switches are a tiny push to make switch labelled "Up", then two LED's and another tiny push to make switch labelled "Dn".

Drive the car at an rpm where you know the exact speed for your gearbox/wheel/tyre combination, and just press either "Up" or "Dn" until the reading is correct.

Thats it.

Steve R · Post by **Steve R** » Wed Nov 09, 2005 2:42 am

Here's the second option:

Did you know that the reading of the GTV6 speedo is adjustable within the speedo itself?

So if your speedo works but doesn't show the correct speed it can be altered by around +- 30 or 40%

Inside the unit theres a small rotary potentiometer that fits a small flat blade screwdriver. You can either dismantle the unit to get to it or drill a hole in the case and adjust it while driving.

Where to drill :
65mm from where the white plasic case meets the black plastic bezel / surround
15mm in from where the white plasic moulding dips 45 degrees.
a 5-7mm hole is plenty big enough
Right below is the rotary pot.

BEWARE the "works" are only 8-10mm below the surface of the casing so if you drill without it disassembled make sure you use a depth stop !! Also ignore that I drilled two holes - the first one wasn't quite in the right place!

Partially dismantle anyway just to make sure there's no bits of plastic swarf rattling around to bung up the works.

With the speedo unscrewed from the dash you can get a screwdriver in and adjust, just pick a known rpm and speed.

Cover the hole to keep dust out, put the speedo back and that's it.

Final and rather obvious safety tip - only calibrate / adjust somewhere away from other traffic !

Plastic Pig · Post by **Plastic Pig** » Wed Nov 09, 2005 3:15 am

Steve,

This is great stuff. Thanks.

I have a 75 TS gearbox/sender and amp unit hooked up to a GTV6 speedo. My speedo underreads by about 10 mph at 80, so I guess my setup is within "tweaking" distance of being put right by the potentiometer. Where's the drill....

Daniel_Jansson · Post by **Daniel_Jansson** » Mon Jan 08, 2007 4:27 am

Plastic Pig wrote:Steve,

This is great stuff. Thanks.

I have a 75 TS gearbox/sender and amp unit hooked up to a GTV6 speedo. My speedo underreads by about 10 mph at 80, so I guess my setup is within "tweaking" distance of being put right by the potentiometer. Where's the drill....

Strange. I just installed a 75 TS gearbox/sender and amp unit to my GTV6 and it unreads x2 ...so in 100km/h it reads about 220km/h.. not so good..

Steve R: Do you think I can adjust this or is it to much of?

x-rad · Post by **x-rad** » Mon Jan 08, 2007 3:39 pm

with the right resistor and capacitor combo, you can halve your timing impulse going to the speedo....

I can remember doing this with the 555ic chip, I just don't remember the necessary combos....

so I bought the unit above..it works well

Daniel_Jansson · Post by **Daniel_Jansson** » Mon Jan 15, 2007 11:34 am

Where is the Potentiometer. Can't find it... wonder if someone have fiddled with my speedo allredy.. some of the soldering (?) don't look original.

I attach a pic of my speedo if anyone can see the potentiometer, circle it and re-post the pic.

Grazie //Daniel

Going to buy the Dakota device soon but right now i just got to get it thru the M.O.T retest. So I need to screw the meter back as much as possible so they hopefully don't notice that it's not going correct... if it's showing x2 they are probably going to notice

Steve R · Post by **Steve R** » Wed Jan 17, 2007 1:36 am

Hi Daniel,

I got your message and had a look at your post.

However, it seems the internals of your speedo are very very different to mine.... mine being a fairly simple looking PCB with a rotary pot (It's the standard UK style with graduations from 10-150 mph)

Sorry I can't help, unless someone else here knows better with regard to swapping components around I suggest you do need the dakota SG1 - which works a treat and is massively adjustable.

S

Daniel_Jansson · Post by **Daniel_Jansson** » Wed Jan 17, 2007 3:22 am

Steve R wrote:Hi Daniel,

I got your message and had a look at your post.

However, it seems the internals of your speedo are very very different to mine.... mine being a fairly simple looking PCB with a rotary pot (It's the standard UK style with graduations from 10-150 mph)

Sorry I can't help, unless someone else here knows better with regard to swapping components around I suggest you do need the dakota SG1 - which works a treat and is massively adjustable.

S

Ok, I will try to do the TUV anyway. Going to order the Dakota device in the end of this month when i get paid

Thanks for the reply /Daniel

GTV6 Speedo reading adjustment