I have a Dishlex Global 300 which is 12 years old and recently the detergent lig won't open during the cycle. I read elsewhere online that there are three things that are often the cause for this to happen: -There is a problem with the timer -The Bi-metal switch or wax motor is bad or not activating -The detergent cup itself If this is the problem, can I fix this myself or do I need to get a technician to do it? Any other suggestions would be appreciated. thanks