I have an LG fridge - model LRTN18320WW that has stopped working. My landlord says that this model needs to be defrosted once a year, but I thought it was frost free. Should I ask him to call a repairman?

Condenser Coils clean or Evaporator Coils clean?

An iced up evaporator coil can cause a freezer not to freeze goods. That is caused by a failed defrost timer or a failed defrost heater.

Or it needs gas topping up.

Faulty defrost I suspect. Could be thermo sensing transducer . Hard to fix as you need to almost defrost fridge before repair man arrives so he can test this transducer works properly when it is cold.

Find your model # and put it in the search box here: http://www.lg.com/us/support . Once your fridge is showing, there is great troubleshooting info available. Also, armed with the model #, we can actually give you pertinent advice!

That does not look like an LG model number, but regardless, it sounds like the defrost system is not working, allowing frost to build up and block air flow over the cooling coils in the freezer (where all the cooling for the entire refrigerator takes place). Take back panel off inside freezer, melt frost / ice with a hair blower. Test for continuity through defrost heater and replace if "open". If it was OK, problem could be deftost control, or as simple as a door not fully closed at some time, allowing excessive frost build up.

Probably be cheaper to get new one, it has probably had the compressor fail or a leak in the cooling system.

I have the same problem with my F&P fridge/freezer although I'm not sure how old it is because I bought it from my landlord when he moved out. I call the repairman who said turn it off and defrost the freezer. I turned it off last night, defrosted the freezer as there was some ice build up internally at the rear and turned it on again. It went fine, I set it at the coldest (gauge on colder) setting and this morning it was quite cold. Today I get home from work and it's hardly cold, no condensation on the lemonade or beer bottles! Will be interested to hear others thoughts before I call the repair man again. thanks, Jenny

If I was of assistance please vote, Thank you. 

Defrost problem. Either defrost heater, defrost thermostat, or defrost timer is bad.

at the very least replace that water filter.clogged water filter will reduce water pressure to the line.