The only additions I may add to the lengthy, but eloquantly described steps below, would be to inspect the elements themselves; occasionally the element which contracts when cold (off) showing a good resistance (Ohms), yet, under load (on), will quickly seperate the split element.
Similar to a loose terminal on a car battery will deduct 80% of its potential to provide power (Amperage) A loose/corroded mating surface on connectors will cause extreme heat and arcing, burning the molecular structure of the copper wire. It will appear black and purplish and be fatigued so inspect connectors and wire condition to terminals which demand Amperage.
Quickie Fix! I have actually taken many a broken element, twist broken ends together, then wrapped the twist fix with a piece of element from a broken toaster to make a solid connection, just may save you money and hopefully not burn the house down so this is possible but not really advisable, some risk exists, exponentially with dirty lint-filled exhaust ports, the hose attaches to.
It is advisable for everyone to clean your vents in the fall to prevent lint buildup, creosote levels in chimneys, and old chimneys must be inspected for loose bricks in their attics close to roof peaks where mortar is missing, flames passing through cracks & holes, licking at wooden rafters.
Global Bonus Tip for home owners: Check for burn evidence where chimneys meet the roof in your attics before operating that fireplace or wood furnace!
East Coast Canada Rocks!
:)