The short answer
A Contoure microwave that runs cold is often set or loaded wrongly rather than broken, and a mug of water at full power separates the two in two minutes. On this class the usual cause is a coach supply that will not sustain the oven, with a power level left set low from a previous programme next to rule out.
What you actually observe
- It heats properly on shore power and barely at all on the inverter — A split by supply is a supply answer.
- Everything takes twice as long as it used to — A gradual change points at weakening rather than failure.
- NEAR MISS: the oven will not start at all — That is a different page, with interlocks and supply at the top of its list.
The causes, most likely first on this brand
- A coach supply that will not sustain the oven — Ranked first on a Contoure unit: an inverter that starts the oven but cannot hold it under load gives a cycle with very little heat in it, and nothing on the panel says so.
- A power level left set low from a previous programme — An oven set to a low power level runs its full time while delivering a fraction of the energy, and nothing about the display makes that obvious. Ranked second here: a small coach panel makes a power level easy to set by accident.
- More food in the oven than the cycle time allows for — Ranked third here: a compact coach cavity is smaller than owners expect.
- A magnetron at the end of its life — Ranked fourth here: last, and a coach oven is usually replaced rather than repaired.
Check in this order, and why this order
- Run the water test on shore power and again on the inverter — A clear difference between the two is the answer without anything being opened.
- Set a short time at full power deliberately and heat a cup of water — Water that is clearly hot after a couple of minutes at full power tells you the oven works.
- Compare the result against a single cup of water heated for the same time — If the cup gets hot and the meal does not, the oven is working and the load is large.
What an owner can safely check
- Switch off other large loads and repeat the test on shore power — A hot cup on shore power and a warm one on the inverter is a supply result.
Tools: mugAbout 15 min
- Clear the panel, select full power explicitly and run a cup of water for a couple of minutes — This is the standard test and it removes the simplest explanation first.
Tools: mugAbout 10 min
- STOP HERE if the next step needs a meter on live terminals or a panel off — That is where an owner check ends and a service call begins.
Before you open anything
Safety
Never remove the outer cabinet of a microwave: the capacitor inside holds a dangerous charge long after the power is off, and that remains true of an oven unplugged for days. Never run the oven empty, and never defeat or tape a door interlock. Use a mug of water rather than food for any test, and take it out with care because superheated water can boil over suddenly.
When to call a technician
Call once the power level, the load, the turntable and the supply are all clean and a cup of water still will not heat, because everything past that point is behind a cabinet an owner must not open. Stop using the oven and call at once if there is arcing or a burning smell. Bear in mind when you decide that an RV appliance is serviced by RV dealers rather than by household appliance technicians, and the warranty usually runs through the dealer who sold the coach.
Nearest pages of this class
What this page does not cover
This page covers the Contoure microwave as a class, not one family or model line. Component arrangements, power ratings and service procedures all change from build to build and are deliberately not here. Where a family or model page exists for your oven, it is the more specific answer and the one to read first.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
