No, this will not replace your A30-3780 cold control. This replaces Ranco #A12-1514.
We do not have anything on our site that will replace your cold control. Perhaps you can get me the model and serial number of your unit and I can find another OEM part that will work.
In case you wrote the model number down wrong, we do have a replacement for a Ranco A30-3730. Please see below.
Ranco A30 cold controls: http://restaurant-supplies.etundra....