We have an old electric oven which has been fine for 13 years. The other day the fan assisted oven was on and then there was a bang, a smell of burning and with this, the oven turned off. After ten minutes, we were able to use both ovens indefinitely at 180 degrees. Water vapour is now evident on the small oven door externally. At higher temperatures, we are ok for ten minutes and then everything goes off. Things can be resumed again later in the same fashion. The fan still seems to be working. Grateful for any advice and hints of costing.