Speed sensor?
 

I am having a problem with the reading on my speedometer. It is WAY off ( faster ).
For example it says I'm doing 150km/hr and my power FC reads 125km/hr. It is off at every speed range while it would appear the power FC is correct. I even had my wife drive beside me and compared the different numbers and again the power FC is correct.
Now I have after market rims (19inch not sure of the over all diameter) so that might be part of the issue. I couldn't tell you if it did this before I upgraded the rims because I didn't have a power fc then to compare plus I only drove it for a week.

How can the power FC and the speedometer read such different things? Any suggestions on how to fix it?

There is only one speed sensor on the 93 seven; it is located in the transmission. As such if you are getting different readings from your pfc and your speedo something is wrong.

There is an adjustment screw on the speedo you can try to fix this by playing with that however the adjustment screw is a pia to get to. The safe way to do this is to take the gauge cluster apart, make an adjustment to the screw, put it all back together and see where you stand; then rinse and repeat. Its a little bit like throwing darts in the dark but it will get you there eventually. The other option with this is to take apart the cluster and modify it in a way that the cluster is functional and the screw is accessible, then just drive down the road while making the adjustments. I have read of someone doing this before on a dyno.

You can also send it off to be refurbed there are still a few shops that do that kind of work and they will guarantee it for whatever amount of time/miles. This is the best option as they will have the equipment to do all of this stuff correctly. It is probably the most expensive.

Another option is to just replace the speedo this will however result in the loss of your car correctly indicating the miles it has been driven. Plus speedos aren't cheap.

And a last option is to take the thing apart and replace all of the capacitors with better ones from digikey in the vain hope that that is your problem.

good luck

If the PFC is correct, and the speedo is wrong, then it's definately the speedo not the sensor.

It could also be that the needle is of. If you don't want to buy a new speedo, and it is generally off a stable amount through the whole range you can adjust the needle, but that would be a compromise.