# How to Fix Whirlpool Error F42 (Heater Relay)
The Whirlpool F42 error code is a critical failure indicator related to the machine’s heating system. This guide will help you understand the error and walk you through the diagnosis, which in most cases, leads to replacing the Main Control Board.
—
## 1. Explanation: What Does F42 Mean?
The F42 error code specifically signals an issue with the **Heater Relay Circuit**.
### In plain English:
The heating element in your washing machine is responsible for warming the water, especially in sanitary or specialty cycles. Power is sent to this heating element via a switch called a **relay**, which is located on the Main Control Board (often called the CCU or Central Control Unit).
When the F42 code appears, it means the Main Control Board detected that the heater relay is either:
1. **Stuck Open:** Not allowing power to the heater when it should.
2. **Stuck Closed:** Always sending power to the heater (a dangerous scenario).
**The most likely culprit for the F42 error is a faulty Main Control Board (MCB), as the relay itself is an integrated, non-replaceable component of that board.**
—
## 2. Step-by-Step Fix and Diagnosis
Before ordering a replacement board, follow these steps to confirm the diagnosis and ensure no simple fix was overlooked. **Always unplug the washing machine from the wall power outlet before attempting any internal inspection.**
### Step 1: Power Cycle and Reset
A temporary electronic glitch can sometimes trigger an F42 error.
1. Unplug the washing machine completely from the power outlet.
2. Wait for 5 to 10 minutes to allow any residual voltage to dissipate.
3. Plug the machine back in.
4. Attempt to run a diagnostic cycle or a simple wash cycle.
If the error immediately returns, proceed to internal inspection.
### Step 2: Visual Inspection of the Main Control Board
The heater relay handles high amperage, and failure often leaves visual evidence on the board itself.
1. **Access the Control Board:** Depending on your model (front-load vs. top-load), you will need to remove the top panel or the rear access panel to locate the Main Control Board (MCB).
2. **Inspect the Board:** Look closely at the MCB, focusing on the area where the wires leading to the heating element connect.
3. **Check for Burn Marks:** If the relay failed due to arcing or overheating, you will often see:
* Scorching or brown marks on the plastic housing.
* Black residue or soot on the circuit board itself.
* A distinctly burnt electrical smell.
If visual damage is present, the Main Control Board must be replaced.
### Step 3: Test the Heating Element (Optional but Recommended)
Although the error code points to the relay, a shorted-out heating element could have caused the relay to fail. It is wise to test the element to ensure the new board won’t fail immediately.
1. **Locate the Heater:** The heating element is typically located at the bottom of the wash tub, accessible from the back or sometimes the front lower panel.
2. **Disconnect Wires:** Disconnect the two main power wires leading to the element terminals.
3. **Use a Multimeter:** Set your multimeter to the Ohms ($Omega$) setting.
4. **Test Continuity:** Place one probe on each terminal of the heating element.
* **Good Reading:** The reading should typically be between **10 to 30 ohms** (check your specific model for exact specs).
* **Bad Reading (Open):** If the meter reads **OL (Over Limit)** or infinity, the heating element is broken and needs replacement.
5. **Test for Ground Fault:** Move one probe to a clean metal part of the machine chassis (ground) and keep the other probe on one of the element terminals.
* **Good Reading:** The meter should read **OL** (no continuity).
* **Bad Reading (Short):** If the meter reads any continuity (low ohms), the element is shorted to ground and must be replaced.
### Step 4: Conclusion
If the heating element tests good (10-30 Ohms and no short to ground), the **Main Control Board** is the definitive source of the F42 error and requires replacement.
—
## 3. Replacement Part Information
Replacing the Main Control Board is a modular swap: unplug the old connectors and plug them into the new board. Ensure you take pictures of the wire placements before disconnecting anything.
**Check the price for a replacement Main Control Board here: https://www.amazon.com/s?k=Whirlpool+Main Control Board&tag=trivian-20**