The nice people at Oakville Appliance Repair sent a polite technician named Lee to my house to fix my Thermador range, as it was heating very poorly for a week. Lee diagnosed the problem and discovered that a faulty wire needed to be replaced. Luckily he had spare wires in his car that happened to be compatible with my range. He completed the repair job in about an hour, it was a little bit more expensive than I expected but I am very happy with the repair work as the range has been working really well since he fixed it.
UPDATE: I have recommended Lee's services to a family friend and he managed to fix their fridge also. Kudos to Oakville Appliance Repair!