the coffee tastes burnt from my black+decker 12 cup, i've tried different coffee and it's still bad

Diagnosis

Mineral scale buildup, primarily calcium and magnesium carbonates, has accumulated inside the internal aluminum heating element and the narrow delivery tubes of your Black+Decker CM1160B. When these minerals crystallize on the heating walls, they create an insulating layer that prevents the element from sensing the water temperature accurately. To compensate, the machine continues to heat the metal surface to a much higher temperature than necessary to move the water. This results in "flash boiling" or localized overheating where the water hits the coffee grounds at temperatures well above the ideal 195°F-205°F range. When water exceeds 212°F at the point of contact, it scorches the delicate oils in the coffee beans, extracting bitter tannins and creating that distinct "burnt" or acrid flavor. You can confirm this by listening for excessive sputtering or "coughing" sounds during the brew cycle, which indicates steam pockets forming due to scale restrictions. Additionally, if the brew time has slowed down significantly compared to when the machine was new, you have a confirmed scale blockage.

How to Fix It

To eliminate the mineral deposits and restore the correct brewing temperature, perform a deep chemical descale using the following precise sequence:

1. Empty the coffee filter basket and remove any old grounds or paper filters. Ensure the glass carafe is clean and empty.
2. Mix a solution of 50% distilled white vinegar and 50% filtered water. For a full 12-cup reservoir, use 6 cups of vinegar and 6 cups of water. Pour this mixture directly into the water reservoir.
3. Start a brew cycle. Once the carafe is approximately half-full, press the "Off" switch or unplug the machine to pause the cycle.
4. Let the machine sit for 30 to 60 minutes. This "soak phase" is critical; it allows the acetic acid in the vinegar to break the chemical bonds of the calcium carbonate scale inside the heating tube.
5. Turn the machine back on and allow the remainder of the vinegar solution to brew completely into the carafe.
6. Discard the vinegar solution. Fill the reservoir to the 12-cup max line with fresh, cold filtered water.
7. Run two full brew cycles with plain water. This removes any residual acetic acid smell and flushes out the loosened mineral flakes.
8. Perform a final "test brew" with your preferred coffee to verify the flavor has returned to normal.

If That Didn't Work

• Deep Clean the Showerhead: The spray head (where water exits into the basket) often collects oily residue and old coffee particles that burn during every cycle. Use a toothbrush and a mixture of baking soda and water to scrub the small holes in the showerhead to ensure water is distributed evenly rather than streaming in one hot spot.
• Check Your Water Source: If you are using hard tap water, the scale will return within weeks. Switch to bottled spring water or a filtered pitcher (like Brita) to prevent the rapid re-accumulation of minerals in the heating element.
• Verify Grind Size: If you are using a grind that is too fine (espresso-style), the water will struggle to pass through the bed of coffee. This causes the water to sit too long and overheat, leading to over-extraction and a burnt taste. Switch to a medium-coarse grind specifically labeled for "Drip Coffee."
• Inspect the Warming Plate: If the coffee tastes fine immediately after brewing but burnt after 15 minutes, the warming plate is overheating the carafe. The CM1160B does not have a programmable timer for the heating plate; if you aren't drinking the coffee immediately, pour it into a thermal carafe to avoid "cooking" the coffee on the hot plate.

Heads Up

• Descaling Frequency: Perform the vinegar descale every 30 to 60 days depending on your local water hardness to prevent permanent heating element failure.
• Avoid Harsh Chemicals: Never use bleach or industrial descalers in the CM1160B, as these can corrode the aluminum heating tube and leak toxins into your brew.
• Filter Maintenance: Always use a high-quality paper filter or clean the permanent gold-tone filter after every single use; old oils trapped in the mesh will oxidize and taste burnt.
• Power Cycle: If the machine seems to be overheating, ensure it is plugged directly into a wall outlet rather than a crowded power strip to ensure stable voltage to the heating element.