Speedo decides when it wants to work or not

[lofapoo]

Very often does my speedo jump. For instance, I'm driving 25, while the needle is rocking between 70 and 110. Sometimes the needle does a full rotation and rests itself against the bottom of the gauge cluster right below the 115 mark, and when I turn the car off it just resets itself back to its normal position. Sometimes it just sits at zero. Kinda sucks when you get tickets for not knowing how fast you were going

Anyone know wtf?

Thanks in advance.

[ILikeMy240sx]

it might be your VSS (vehicle speed sensor) or your speedometer unit.

Pull your VSS and see that you get approx .5V drop when you spin the pinion gear.

If the VSS works then its most likely your speedometer

[lofapoo]

Would you care to explain a little further?

Where may I find my VSS and how would I check the voltage drop? I'm more than sure my dad has a tool to check the drop I'm just wondering where I'd connect it to.

Thanks for your help

[ILikeMy240sx]

VSS is at the end of your transmission where the drive shaft is. It is on the passenger side. 3 O'Clock position.

Get a multimeter and measure the voltage drop across two terminals of the VSS while spinning the gear.

BTW, you have to drain the transmission fluid before you take it out.

[lofapoo]

Cool I'll be sure to check it out sometime.

Thanks for your help.