An E1 fault can mean a few different things depending on which appliance it is we’re refering to.. you need to post the make and model (it’s probably a baxi or potterton, main) is it flasing on and off and alternating with another number or just flashing e1? Ignore ‘mystic megs’ blind diagnosis as altho it may turn out correct it’s by luck and not skill. A true diagnosis can only be made using the correct codes for your specific model of boiler.
Phill Dee, March 2018