The short answer
On a Cove dishwasher that has been in service for years, a cool result usually means scale on the heating circuit and a supply that has degraded, rather than a failed part. The machine will often compensate by running longer rather than reporting a fault, which is why owners describe cycles that have grown rather than heat that has stopped.
What you are actually seeing
- Cycles have grown steadily longer over a year or more — Means: on-page
- The tub is warm but never hot, where it used to be too hot to touch — Means: on-page
- Drying has faded gradually rather than stopping — Means: on-page
- Visible scale in the base of the tub — Means: on-page
- The machine performs better on a long cycle than a short one — Means: on-page
- The machine will not run a cycle at all — Means: different-fault — Go to: cove-dishwasher-wont-start
- Dishes clean but wet with a warm tub — Means: different-fault — Go to: cove-dishwasher-cleaning-performance
- Body: Match what you see before you take anything apart. Cycles have grown steadily longer over a year or more. The tub is warm but never hot, where it used to be too hot to touch. Drying has faded gradually rather than stopping. Visible scale in the base of the tub. The machine performs better on a long cycle than a short one. Some near-miss symptoms belong on a different page: The machine will not run a cycle at all points at a start or supply fault, covered on cove-dishwasher-wont-start; Dishes clean but wet with a warm tub points at a drying rather than a heating problem, covered on cove-dishwasher-cleaning-performance.
Causes, ranked for this machine
- Scale insulating the heating circuit — Why this rank: First on an older machine because scale builds on the hottest surfaces and produces exactly this slow decline
- A water hardness setting that has never been matched to the supply — Why this rank: Years at the wrong setting is what allowed the scale to build in the first place
- A temperature sensor that has drifted, so the control stops heating early — Why this rank: A drifted sensor leaves the machine thinking it is hot when it is not
- A house hot supply that has degraded, such as a scaled water heater — Why this rank: Worth checking on an older house as well as an older machine
- A heating circuit at the end of its life — Why this rank: Last because it needs a part, and on a machine of this quality it is a worthwhile repair rather than a reason to replace
- Body: Ranked for a premium built-in dishwasher: hard-plumbed, on a dedicated supply, installed under a worktop by a fitter, quiet by design, with hand-cleaned filtration and a condensation dry that depends on rinse aid. Most likely: Scale insulating the heating circuit. First on an older machine because scale builds on the hottest surfaces and produces exactly this slow decline. Next most likely: A water hardness setting that has never been matched to the supply. Years at the wrong setting is what allowed the scale to build in the first place. Third: A temperature sensor that has drifted, so the control stops heating early. A drifted sensor leaves the machine thinking it is hot when it is not. Fourth: A house hot supply that has degraded, such as a scaled water heater. Worth checking on an older house as well as an older machine. Fifth: A heating circuit at the end of its life. Last because it needs a part, and on a machine of this quality it is a worthwhile repair rather than a reason to replace.
What to check, in order
- Look into the base of the tub for scale before anything else
- Run a descaling cycle and judge whether the tub temperature improves
- Check the water hardness setting against your supply
- Compare a long cycle against a short one
- Body: Each check rules out the causes above it. First, look into the base of the tub for scale before anything else. Second, run a descaling cycle and judge whether the tub temperature improves. Third, check the water hardness setting against your supply. Fourth, compare a long cycle against a short one.
Checks you can safely make yourself
- Open the door and look into the base of the tub with a torch for white scale deposits — Tools: torch — Time estimate: a few minutes
- Run the hottest cycle with a proprietary descaler and an empty machine, then repeat a normal cycle and feel the door — Tools: descaler — Time estimate: two long cycles
- Check the water hardness setting and adjust it to match your supply according to the markings — Tools: none — Time estimate: a quarter of an hour
- Run a long cycle and a short cycle on separate days and note how much the results differ — Tools: notepad — Time estimate: two cycles
- Check the household water heater setting and how long the kitchen tap takes to run hot — Tools: watch — Time estimate: a quarter of an hour
- Body: Checks an owner can make with the machine switched off at the breaker, or by watching a cycle. Step one: Open the door and look into the base of the tub with a torch for white scale deposits. Tools: torch. Time: a few minutes. Step two: Run the hottest cycle with a proprietary descaler and an empty machine, then repeat a normal cycle and feel the door. Tools: descaler. Time: two long cycles. Step three: Check the water hardness setting and adjust it to match your supply according to the markings. Tools: none. Time: a quarter of an hour. Step four: Run a long cycle and a short cycle on separate days and note how much the results differ. Tools: notepad. Time: two cycles. Step five: Check the household water heater setting and how long the kitchen tap takes to run hot. Tools: watch. Time: a quarter of an hour.
Safety first
Safety
Switch off at the breaker before removing any panel. The heating circuit is in the base of the tub with mains terminals beside it and it stays hot after a cycle, so do not reach into the sump immediately after a wash. On a machine of this age, remember that the door carries a custom panel under spring tension set years ago: do not loosen door hardware, and treat any water reaching fitted cabinetry as urgent rather than cosmetic. Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. unplug-before-service
Where the owner fix ends
On an older machine, call a technician once it has been descaled, the hardness setting matches the supply, the hot supply is proven and the tub is still never properly hot. A heating circuit or a sensor on a machine of this quality is normally worth repairing, given the cabinetry work involved in replacing an integrated machine.
Nearest pages of the same kind
Generalized information
This page is generalized across the Cove dishwasher line. Fully integrated machines carrying a custom cabinet panel and machines with a finished front share the ranking above but not every part, and this page does not cover a specific model, control revision or installation. Family- and model-specific pages, where they exist, are linked below.
Links: - [Common COVE Dishwasher Problems](/blog/cove-dishwasher-problems) - [Cove Dishwasher: Abnormal Noise or Vibration](/blog/cove-dishwasher-abnormal-noise-2) - [Cove Dishwasher: Does Not Clean or Dry](/blog/cove-dishwasher-cleaning-performance-2) - [Cove Dishwasher: Controls, Display or Error Code](/blog/cove-dishwasher-control-fault-2)
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
