Testing your block heater is essential to ensure it's functioning correctly and ready for cold weather. While dedicated block heater testers or "boxes" exist, as mentioned in the reference, not everyone has one readily available. A common and effective way to test a block heater involves measuring its power draw using a multimeter set to measure amps (current).
Understanding Block Heater Testing
A block heater is essentially a heating element that warms your engine's coolant or oil. Like any electrical heater, it should draw a specific amount of power (measured in watts) when plugged in. This power draw is related to the voltage (standard house current) and the current (amps) it draws.
- Purpose of Testing:
- Verify the heater is operational.
- Check if it's drawing the correct amount of current.
- Identify potential issues like a failed element (zero current) or a short (excessive current).
Using a Multimeter to Test Current Draw
The reference suggests an alternative method for testing if you don't have a specialized tester box: "Take your multimeter swap it to amps plug it through the box." This implies using a multimeter to measure the current the heater is drawing.
Here's a general process, adapting the reference's suggestion:
- Safety First: Ensure the block heater cord is unplugged from the power source before handling connections.
- Locate Specifications: Find the wattage or amperage rating for your specific block heater (often printed on the cord or element). This tells you how much current it should draw. If only wattage is listed, you can estimate the expected amps using the formula: Amps = Watts / Volts (use 120V for standard household outlets).
- Prepare Your Multimeter:
- Select the amperage measurement function on your multimeter. Choose an AC Amps range suitable for the expected draw (e.g., 10A or 20A range, as most block heaters draw between 4 and 10 amps).
- Move the multimeter's probes or leads to the correct jacks for measuring high current (typically labeled "A" or "10A" and "COM").
- Connect for Measurement: You need to measure the current flowing through one of the wires supplying power to the heater while it's operating.
- Clamp Meter Method: The easiest way is often using a clamp-on ammeter. You simply clamp the meter around one of the power wires of the block heater cord after it's plugged in and drawing power.
- Inline Method (Less Common for High Amps): The reference phrase "plug it through the box" and "plug it through the box" alongside measuring amps with a multimeter suggests a setup where the power cord is routed through a testing jig or even potentially breaking into the circuit to insert the multimeter in series with the load. This method is more complex and potentially hazardous if not done correctly. A clamp meter is generally safer and simpler for measuring AC current draw.
- Apply Power: Plug the block heater cord into a standard 120V AC outlet.
- Read the Multimeter:
- If using a clamp meter, note the reading displayed.
- If using an inline method (as potentially suggested by "plug it through the box"), the multimeter screen will show the current reading.
- Interpret the Results:
| Multimeter Reading | Interpretation | Action |
|---|---|---|
| Zero or Near Zero | Heater element is likely failed or open circuit. | Replace the block heater. |
| Close to Spec | Heater is likely functioning correctly. | No action needed. |
| Much Lower | Partial failure or low voltage supply. | Investigate cause; potentially replace heater. |
| Much Higher | Possible short circuit or internal damage. | Immediately unplug; replace block heater. |
Dedicated Block Heater Testers
As the reference notes, specialized "boxes" for testing block heaters exist. These might offer a simpler plug-and-play solution, potentially displaying wattage or an indicator light based on current draw, but the underlying principle is still verifying the heater is drawing the expected amount of power when connected to voltage.
By measuring the current draw with a multimeter, especially a convenient clamp meter, you can effectively test your block heater's functionality, integrating the method suggested in the provided reference.
