No, I have no idea what the temperature variations are in the fridge, neither with or without timer. Maybe the small thermometer for projects like this should be moved up on the to-get list?
EDIT (2011-03-15): I got a small indoor/outdoor digital thermometer with min/max yesterday
Last night the temperature inside the refrigerator was between 3.9°C and 4.9°C (39°F-41°F) without a timer. I'll keep an eye on it for the next few nights, then put the timer back on.