Check to see if it has a temperature adjustment screw/knob. Mine had a course and fine screw. BE CAREFUL as you can ruin your kegerator if you unscrew this too far! I made small adjustments over time and monitored the temperature with a thermometer. Went from too warm to to almost frozen and then backed off to get where I wanted it to be. Seems to vary a little with time of year and humidity...but saved me from having to buy another temperature controller and dealing with that. YMMV. Cheers!
I don't think the adjustment screw is going to do any good in this case since the picture shows the thermostat set to "off" and it's freezing the lines. I could be wrong, though. I did try and adjust mine that way, but that made it always on or always off. Stonebrewer is right, though. It's worth a try to see if you can get it back to where you want to be without buying anything.
did the thermostat on your fridge have two or three wires coming out of it? mine's got three and it looks like the controller only works for one with two.
edit: just now understanding that this is the whole thing, not something that just wires into the sensor with the original thermostat. thanks for the help.
Yeah, mine had three wires: light blue, gray, and green. Green was, of course, ground; I think gray was the hot wire, running to the black wire on the cord; and then I think blue was the (sometimes hot) wire running to the compressor. The thermostat is essentially just a mechanincal on/off switch controlled by temperature and adjustable to kick on at a range of temperatures, thus supplying power to the compressor.
I just went ahead and clipped both those wires back by the compressor and so there was nothing running through them. That made the ground up into the fridge compartment unnecessary, but I made sure I grounded it underneath for safety purposes. Then the two wires that would run up to the thermostat I wired into the "cooling" section of my controller, made sure that power was also running to the controller from the power cord and that the neutral was correctly routed to the compressor and the controller and then I was good to go. I cut a hole in the side of the fridge down in the compressor compartment to mount it to.
If none of that makes sense, there should be a wiring diagram on the back of your fridge to help make sense of what wires go where and a number of threads on how to wire a controller into it.
On the other hand, if you don't feel like wiring anything and your compressor is always on, you could just plug it in to an external controller and you'd still be just fine. I found, though, that by freeing up the space taken up by my original thermostat (it was on the side instead of the top like yours) allowed me to squeeze in an additional keg with some creative trimming of the shelving.