Final answer:
The oil temperature bulb is usually located in the engine block, cylinder head, or oil pan. It sends voltage output proportional to the oil's temperature to the temperature gauge on the dashboard of a vehicle.
Step-by-step explanation:
The oil temperature bulb, or sensing unit, is typically located in areas subject to the engine oil temperature, often threaded into the engine block, cylinder head, or oil pan.
In some vehicles, like the one mentioned in Figure 10.34 of a 1996 Volkswagen, the temperature gauge on the dashboard is a voltmeter that registers the voltage output of the sender units. These sender units produce a voltage that is expected to be proportional to various conditions such as the amount of gasoline in the tank and the engine's temperature.
In the case of the oil temperature, the sender unit corresponds to the oil temperature bulb that detects the oil's thermal state. This information is then conveyed through electrical signals to the gauge on the dashboard, ensuring the driver can monitor the engine's temperature effectively to prevent overheating and any related engine damage.