Thermo Fan Switch
Thermo Fan Switch closes the cooling fan circuit when the engine coolant reach the temperature which it been designed.
 |
| Water Temperature ( Degree ) | Resistance ( R ) |
| 21 | 2.7 |
| 25 | 4.8 |
| 30 | 6.1 |
| 35 | 5.1 |
| 40 | 4.4 |
| 45 | 3.2 |
| 50 | 2.6 |
| 55 | 1.3 |
| 60 | 0.8 |
| 65 | 0.7 |
| 80 | 0.7 |
The graph:
The TFW is faulty one. Because it is a switch, the resistance should be OL when it is opened, very low and constant resistance when it is closed.
The internal operation shows below:
The switch has 2 terminals, one ground and one voltage in. The voltage in terminal inside the switch constructed by 2 different types of metal. When the temperature raise up, the metal expand, one kind of metal expand more than the other one, so the terminal inside the switch bend to the ground terminal. When the temperature is high enough, the voltage in terminal contact to close the circuit to switch on the cooling fan. Also the the temperature goes down, the voltage in terminal bend backward and disconnect to ground terminal and turn off the fan.
does this switch meet manufactures specifications?
ReplyDeleteThis one doesn't switch until 90 degrees