I have a strange speedometer issue. According to my gps calibration testing, it is accurate between approximately 50 mph and 70 mph. Over that, it reads high - e.g., at 110, I'm actually doing 95 to 100. It gets further out as I go faster.
On the low side, the reverse happens - it reads lower than what I am travelling - at 20 mph, it shows around 5 mph or less.
I have a 170 mph unit, and I believe it is the original unit (I have all service records, and it was never swapped out).
What could be the problem, and what is the fix?

 

It sounds like it's out of calibration and needs to be sent it to get recalibrated. IIRC, there is a company in california that specialized in this for speedo's. I can't remember the name, but hopefully someone else will. Also, a search on speedos will probably pull the name up also...Good Luck!

 

Join the club.
jp 83 Euro S AT 52k

 

Probably mean Palo Alto Speedometer Inc.

 

Interesting - how would calibration issues cause this type of problem? It seems that it would be out the same way all the way thru - i.e., either reading low or reading high. Not flip flopping like mine does.