STRANGE Speedometer Issue

[topless98gt]

Ever since my car was broken into (March 2008), my speedometer has not worked correctly. I have a DM SpeedCal installed, so when they ripped out the center console, they took the power for the SpeedCal with them. I tried giving it dedicated power, that did not work.

So finally, when I got around to getting a new center console in October 2008, I hooked up the new 12V cigarette lighter socket, and the fog light switches. The speedo appeared to work correctly. But this was at low speeds.

Pay attention, because this might actually confuse you...I bet you've NEVER heard of this problem before.

So the problem now is:

Speed less than 40mph, speedo works fine under all conditions.
Speed over 50mph, speedo DOES NOT work under any conditions.
Speed over 40mph and less than 50mph ONLY works when my foot is not resting on the clutch.

Let me say that again...if I am driving between 40mph and 50mph and I have my foot completely off of the CLUTCH pedal, the speedo works fine. If I rest my foot on the clutch pedal, the speedo stops working. This only affects BETWEEN 40MPH AND 50MPH.

One more time, just in case you're still confused:
- 43MPH (greater than 40MPH and less than 50MPH), foot IS NOT RESTING on clutch = speedo works
- 43MPH (greater than 40MPH and less than 50MPH), foot IS RESTING on clutch = speedo DOES NOT work
- 37MPH (less than 40MPH) = speedo works fine under ALL conditions
- 53MPH (greater than 50MPH) = speeds DOES NOT WORK under ANY conditions

Any ideas now that I may have puzzled your mind?

 

[sgarlic]

Have you checked the wire that runs underneath yet (the VSS wire) ? My hunch is that the wire running underneath the car from the speedcal got half ripped out and could be shorting on something metallic every time you touch the clutch. At speeds above 50, the wind force underneath the car could be blowing the wire into something metallic and holding it there, thus shorting it out without the need to have the clutch pushed in or touched.