Most likely. Those little black boxes are well known for going wrong.
Could also be a disloged / shorted / bridged earth connection behind the clocks - also as a result of chopping about with the wires to fit the convertor or less commonly a shorted track on the flexi circuit "board" on the back of the clocks.
Whatever, you will need to get the clock pod out and have a look..... should be fairly obvious once you have sight of the wiring.
Will take you about 4 hours to get the clocks out the first time you do it and about 20 minutes every time thereafter once you know how
There's plenty of posts about how to do it and in what order on here if the Search will let you find it! If not say and I'll give a blow by blow.
Cheers
Graham
