We had a similar problem recently. If the spanner symbol is showing, your fridge display may show a fault code too??
Our problem ended up being with the change over relay. First, we adjusted the dial on the relay to make it less sensitive. This worked fine. Then the problem returned. This time It turned out to be the inline fuse if the 12v direct power cable from the battery. The fuse was t actually blown, but the metal part was cracked, but held together by the outer plastic case. A new fuse was installed and all fine again now. The peas stay frozen!
Might not be, but could be either of these?