Bosch HME9760 Microwave Oven "er4" Questions

...applied, top display illuminates and the fades after approx. 10 secons. Bottom display then reads ER4 - I think this means Error number 4? No fans work and the oven appears dead apart from a the

HME9750 error Er4 My microwave is not working anymore. The fuses are ok. On the lowest screen you can hardly read Er4 (in the sun). On the upper screen there is the time, but you can hardly read that ...