freezer freezing up with ice on coils(mostly on top) not cooling fan is running.This hppened two months ago and after turning it off and letting it defrost by itself (no power) it has worked fine until yesterday. froze up again i thawed it with a blow dryer and cut it back on i t is froze up again today. I've move my food to another freezer. I'd like to have a service manual or at least troubleshooting instructions. I unbderstand electronics just need to know what and where to test.