Replace the motor in my fordescort zx and the speed thermometer wont work

unfortunately a thermometer measures temperature not speed so it will not indicate vehicle speed
I take it that you are referring to a speedometer that does measure speed of a vehicle
it is driven either by a cable , sender unit and wires from the transmission or by the VSS sensor in the transmission.
take it to an accredited service center to have the problem properly diagnosed and a quote
probably the sender unit on the transmission is faulty

no idea what a speed thermometer is and what it does in the vehicle
all well and good with what you have done but the ECM for each vehicle will be different and so will be the TCM
the change is not just mechanical but will require a lot of electronic changes as there are too many years development between the transmissions

It would be the resistor pack, not the motor. If the motor works on any speed, it is good.

The resistor bank is bad for slow speeds, the switch is bad for high speed. In your test, you have voltage, but the switch wont carry the amps, to run high speed. Open circuits will not blow fuses. Replace both switch and resistor bank for all speeds. Make sure to clean leaves and trash from fan housing and see if fan spins freely.

On the wiper motor is the speed control circuit board under the wiper motor cover, replace it.

When they won't park it's 99% need new wiper motor

Sounds like an blower motor resistor. It regulates voltage going to the motor depending on what speed you select. Speed one , or low only lets so much voltage to the motor and full lets all the voltage through. If it is blown, it cannot regulate voltage and acts like its not there. I would start with that.

sounds like the switch and is fairly easy to remove and replace the switch ..

You might want to have your radiator checked to make sure it isn't partially plugged, or try a manual thermometer in the radiator fill hole and se what the temp actually is in case your temp guage is faulty.A candy thermometer works well for this test.

Disconnect connector at blower under pass side of dash.Check for power & ground with the blower switch in the #4 speed (High).Most Likely a blower motor if all 4 speeds are out.If high works but no other speeds,you need a blower resistor.Blower easy to change 3 screws & one connector.hope this helps