If your car heater only works on the highest setting, it’s likely due to a faulty resistor in the heater blower motor circuit. In most vehicles, the heater fan speed is controlled by a resistor pack that regulates the voltage to the blower motor. When the resistor pack fails, the blower motor usually defaults to the highest speed setting, bypassing the resistors.

To fix this issue, you’ll typically need to replace the resistor pack. It’s a relatively common problem in cars and can usually be resolved by a qualified mechanic. However, it’s always a good idea to have a professional diagnose the issue to ensure that it’s not caused by something else.

If your oil heater is not working, there could be several possible reasons:

1. Power Supply Issue: Ensure that the oil heater is plugged in properly and that the power outlet is functioning. Sometimes, a tripped circuit breaker or a blown fuse could be the cause.
2. Thermostat Setting: Check the thermostat setting on the oil heater. If it’s set too low, the heater might not turn on. Try adjusting the thermostat to a higher temperature setting to see if the heater starts working.
3. Faulty Thermostat: If the thermostat is set correctly but the heater still doesn’t work, there might be an issue with the thermostat itself. It could be malfunctioning and not signaling the heater to turn on.
4. Internal Component Failure: The heating element or other internal components of the oil heater could be faulty or damaged. If this is the case, the heater may need repair or replacement.
5. Blocked Airflow: Inspect the heater to ensure that there are no obstructions blocking the airflow. Dust, debris, or other objects could restrict airflow and prevent the heater from working effectively.
6. Overheating Safety Feature: Some oil heaters have built-in safety features that automatically shut off the heater if it overheats. If this happens, allow the heater to cool down for some time before attempting to turn it on again.

If you’ve checked these potential issues and the heater still isn’t working, it may be necessary to consult the manufacturer’s instructions or contact a professional for further assistance or repair.

The time it takes for a car heater to start blowing warm air can vary depending on several factors:

1. Engine Warm-up Time: If the car’s engine is cold, it will take some time for it to warm up to operating temperature. The car heater relies on the engine’s coolant system to produce warm air, so until the engine reaches its optimal temperature, the heater may not blow warm air.
2. Temperature Setting: If the temperature dial is set to a high heat setting, the heater may start blowing warm air more quickly compared to lower settings.
3. Weather Conditions: In colder weather, it may take longer for the car heater to start blowing warm air, especially if the engine coolant needs to heat up significantly.
4. Vehicle Design: Some vehicles have more efficient heating systems than others, which can affect how quickly warm air is produced.

In general, you can expect the car heater to start blowing warm air within a few minutes of driving, especially if the engine is already warm. However, during cold weather or if the car has been parked for an extended period, it may take longer for the heater to reach its full effectiveness.