i have a 99 honda accord ex (manual, 2 dr, 85K mi., bought used in april 2006) and the needle of the temperature gauge always pins at all-the-way hot as soon as the car turns on. the car has never overheated while i’ve been driving it. i’ve had several mechanics swap out the sensor cluster that includes the temp gauge and the problem persists - anyone have any ideas? the spedometer also reads about 10 mph too fast. not sure what that’s about either.
The temp gauge likely has a short or open somewhere in the wiring. The speedometer needs to be adjusted to correct it, if it is off that far. It is normal to be off about 3-5% and it should read too fast. They are designed to do that to prevent speeding tickets due to speedometer error.
How to correct it depends on the specific model, some need to be mechanically adjusted others can be adjusted by computer.
If you are not using tyres that do not match the circumference of the OEM tyres then that could be the cause.
I agree with JEM on the wiring problem. If the temp sensor and gauge have been replaced and the trouble still exists then the wire to the sensor needs to be checked for a problem. Since the gauge is pegged out there may be a short to ground on the wire to the sensor.