Speedo

[Barkychoc]

Norman don't die of shock, I have finally got round to looking at it!

Here's the test setup



Yes Norman that is the same sender you sent me covered in sh!t!
I gave it a bit of a clean.
Don't panic the cog comes off the end by removing a circlip.
The output from the sender is a nice crisp 12v square wave that varies in frequency accoring to the speed (as you'd expect).



Each cm vertically represents 2 volts, so 6 squares = 12 volts.
You can see the volts/div control to the botton right of the pic if you're interested.

Anyway I have spent a lot of time trying to work out the speedo problem to the point that I have just ordered some electronic components, I hope thats OK Norman.

If I'm right then I'll return a fully working speedo to you free of charge.
I have so far identified one problem with the speedo - there may of course be a second fault once that is resolved.

Watch this space!

[Barkychoc]

Both sender and speedo are from a V6 so S2 to S4 are the same as this (2.9 models before the S1.5 owners get upset!)

[Barkychoc]

If that sensor is your problem it might be worth trying to open it up - the one I have looked at looks like it is all metal but on closer inspection it looks like 2 seperate parts glued together - there is a glue line if you look carefully.

[Barkychoc]

blues3 said:

I'll give it a go. Do you recall if the sensor you had felt 'notchy' when turned?

Yes definately notchy - like each notch is being held by a magnet if that makes sense.

[Barkychoc]

I'll have a look in a bit as its still setup on the bench - I can follow the wires from sensor to speedo.

[Barkychoc]

I just had a thought about your raggy waveforms on the scope above - when I tested as above I had a speedo in the circuit - I'm just wondering if your rough waveforms were due to no load?

[Barkychoc]

I guess we could be getting confused here - as I have a sender unit and a speedo but no car loom in between - I've wired it as per this

http://www.tvrsseries.com/drawings/tvrswiringdiagr...

N - Black
B - Brown
Y - Yellow

Regardless I have it wired correctly as I have Voltage on the correct pins of the IC's and the speedo signal going through the first amplifier.