This guide will help you in diagnosing the issues which are related to the Hotend and carriage components.
Tools required- 3mm Allen Key
1. Hotend: Hotend consists of 2 major components

Heater Cartridge

Thermistor
a. Thermistor- The Thermistor is the temperature-sensing device of the Hotend. The input from the thermistor is used by the machine to check the nozzle temperature.
In case the thermistor is not performing as required, you need to check the thermistor using a multimeter.
Steps:
1. Disconnect the Hotend wires from the machine.
2. Set the Multimetre to Resistance mode. Set the range to 100 k Ohms.
3. Connect the two terminals of the Thermistor to the Multimeter.
Note: The Thermistor reading should be taken at room temperature and should not be taken when the hotend is hot.
4. The resistance of the thermistor is 100K Ohms. Due to fluctuation in room temperature, the resistance will be approximately 90 °C.
If the resistance is offsetting too much from the correct values, it indicates there is some issue with the component.
If the part is showing correct resistance values, then you have to check the wiring/connectivity of the printer.

Checking the resistance of the thermistor.
b. Heater Cartridge: The Heater cartridge is used for heating the nozzle. A failed heater cartridge will fail to heat the nozzle to the required temperature and result in improper printing. In case the heater cartridge is not functioning properly, you can check it using a multimeter.
Steps:
1. Disconnect the Hotend wires from the machine.
2. Set the Multimeter to Resistance mode. Set the range to 2-digit reading.
3. Connect the two terminals of the Heater cartridge to the Multimeter.
Note: The Heater cartridge reading should be taken at room temperature and should not be taken when the hotend is hot.
4. The resistance of the thermistor of the thermistor at room temperature will be between 14-16 ohms for a 24V heater cartridge and around 4 Ohms for a 12V heater cartridge.

Checking the resistance of the 24V 40W heater cartridge.
If the part is showing correct resistance values, then you have to check the wiring/connectivity of the printer.
If the resistance is offsetting too much from the correct values, it indicates there is some issue with the component.
Note: If you do not get any reading in the multimeter, the wiring may be the issue. Check the wiring once to make sure there is not damaged/broken wire.