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does any one know how to actually test the speedo?

i am trying to find which side it playing up!

the sender is 75 3L gearbox (3wire) and the speedo is 87 gtv

last time it worked was before we dynoed it ober 200km then some times.. then dead.

beats me.

cbf fixing it. been 2 years now. maybe its time to.

Hi again,

I know got my speedo to work properly again, and the sollution was just a lie away.......

The former owner didn't tell me the truth when I asked him what he had switched the original gearbox with. Not that I believed him fully either but, why lie when I already bought the car. If he lied before to be able to sell it is understandable, but this isn't!!

Before I began to cut wires for the amplifier I bought, I tried to mount just the speedo from the 86 GTV6...... and it worked...
I already knew that the gearbox had the original ratio, but that could point in several directions and didn't give me the answers I was looking for..

I know have a working speedo again without doing anything but to switch speedo, but I still don't know what kind of gearbox I have. A wild guess is that it is a GTV6 gearbox, late version.. but I don't know for sure..

This might be the solution for others as well, so its well worth to try before tearing your electrical system apart.

PS. Why aren't the gearboxes marked with an identity? Grrrr

The speedo needs 3 things connected - power, earth and signal.
To test it, you need to provide all of these and the signal required is a 0-12v square wave. Depends on the trans as to the frequency. My speedo is a GTV2.0 one and 270 Hz = 240 km/h. GTV6's will require a different frequency but this will give you a starting point. Good luck.

Daniel wrote:The speedo needs 3 things connected - power, earth and signal.
To test it, you need to provide all of these and the signal required is a 0-12v square wave. Depends on the trans as to the frequency. My speedo is a GTV2.0 one and 270 Hz = 240 km/h. GTV6's will require a different frequency but this will give you a starting point. Good luck.

As I said, The speedo is now ok again!

Sorry for the confusion, I was answering GTV6GPTT's question on testing a speedo.

No worries!

I'm still with the GTV6's speedo and the Milano's sender combination problem. I tested my speedo yesterday at the laboratory with an oscilloscope and a signal generator. I fed the speedo with 12V DC and a sinoidal signal with 12V (peak-to-peak) and trying different frequencies, I got the following results:

267 Hz => 220 Km/h
242 Hz => 200 Km/h
217 Hz => 180 Km/h
192 Hz => 160 Km/h
172 Hz => 140 Km/h
145 Hz => 120 Km/h
114 Hz => 100 Km/h
88 Hz => 80 Km/h
65 Hz => 60 Km/h
40 Hz => 40 Km/h

Now I need to know what frequency provides the Milano's sender at certain revs...

I don't know if you know, so here is the additional information I found out during my way to a solution of the speedo problem.

There were 3 different speedos mounted in GTV6 through the years, all with different turn/reaction values if you know what I mean. You can find the information about your speedo on a sticker attached at the back of the speedo housing. The one I got from the 86 GTV6 had 0.5 meters/turn if I remember right, which my original didn't have.

/Jonas

great info guys.

trying to figure out which end is playing up, need a simple way.

test light type deal.




besides that my gtv6 speed is difrent from the others this can be a problem. even a late 86 wasnt the same. confusiong :+