how can i find the problem and fix it?

I have two karchar powerwash machines, one not working and the other seems to be going the same way before the other one stopped working. One is a B403 and other is KB9030. The machines problem was when using the washer and just finished a wash, while the machine was just waiting, it would stutter from the unit every ten seconds or so, you could still use it and no power loss from machine till it got worse and the unit gave no power when washing.