Speedometer and Window defroster

The speedometer sounds like a short. The could be a loose connection, either a wire, connector, or a circuit board problem. You may have to do some digging to find the problem and it will probably turn out to be the speedometer itself or the Variable Speed Sensor. Tough one to track down.

The defrost, it the motor of the fan blowing or is it blowing and not getting air on the windows. If the latter is the case, it could be the knob on the dash is slipping or stripped. Check out the knob and after that you are in to other under the dash components for the defrost. If that is the case, deal with both of the problems at the same time.

Manuals don't necessarily cover the problem you have but they cover the removal and replacement of the components that you are talking about.