The top oven on our Bosch double oven isn't getting to temparature. It does get warm but not hot enough. It's over 15 years old> Is it worth getting someone out, or time to replace??
You wouldn't if you saw the state of our kitchen at the moment! Totally gutted it, now waiting for kitchen fitters to fit the new one
I'm telling you, every house should have one! @fired, have you tried recalibrating the oven? It may just need that. Failing that, the thermostat may have gone and needs replacing - easy enough to do yourself.
If there's nothing wrong with the oven when it is operating normally, I'd get it fixed or at least a diagnosis. Unless you are angling for a new one or kitchen. Changed the fan on our Bosch, came out easy. £16.
May depend on how much money you have, and how much you are willing to have a go at DIY, but here is my contribution. I am no DIY expert at all, but it can be very easy and cheap to replace the element yourself. The one catch is that it might be your thermostat rather than the element which needs replacement. More likely the element. I have replaced the main oven element on an oven twice now. You can get good videos online, sometimes for your specific make of oven, but they all have the same build roughly. - The new element was £10 online, and delivered next day. You just need the model number for the oven, and then google it. Don't buy directly from Bosch, it will cost loads more. Obviously turn off oven at mains before starting. It is mostly an easy one man job, but you might need another pair of hands to lift out the oven from the unit. With a small table or similar in front of the oven, you can lift it out onto the table, and the mains wire will be long enough to not need disconnection (Couldn't have been put in otherwise!) A few screws/ bolts will be your only hurdles, but you may need a good range of scredriver bits to fit all bolts/screws. If you don't fancy the challenge, it will be at least £50 to get a man across your threshold!! Why not have a look before booking someone in? Honest, mine was dead easy and safe. If you come across problems, just call the man in then.
You always mention your famous multimeter as being able to diagnose something but I can never work out how it would be useful in the situation you mention