Hello, I have an ice maker model RIC-100. Even though tank is full, "add water" light remains on. Can you help?

Probably water level sensor bad or damaged. Possibly connections to it are loose or corroded.

Don't know if this will help: http://nostalgiaelectrics.com/product/ric100-retro-series-50s-style-automatic-ice-maker/

My Nostalgia Ice maker shows low water, but there is water up to the fill line.

Sounds like the intake line at the entrance to the refrigerator is plugged with lime residue. It has a needle valve in the center and will clog with foreign material, this can be cleaned out by forcing compressed air pressure backwards thru this connection to remove tiny particles inside.

Mine was having the same issue. The trouble-shooting section of the owner's manual mentions cleaning it but doesn't state where it is at. When I contacted Dometic they stated it is in the center of that circular hole in the bottom of the water resovoir, however, they couldn't tell me how to remove it.

Through trial and error, I found that it's just a little basket that fits snugly inside that hole. You DO NOT have to remove the round part that you can see. I used a pair of pliars in an attempt to remove the entire thing and the little basket (looks like a clear plastic thimble) came right out of the center. (If you have good hand strength you can likely just pull it out without using pliars.) I cleaned that off, placed it back into the ice maker and we are back in business. It is making ice as it should now.

I have the SPT IM-100 Portable Ice Maker. After about 2 months, it stopped, telling me that it needed water, when of course it was full of water. I did alot of digging on the Internet to find a solution. There was none. It finally occurred to me that the water sensor might be calcified with our hard water here in Reno. BINGO!!!! I ran several cycles with lemon juice and vinegar (you pick your favorite non-toxic acid), and the damned thing started up again as if brand new.

my one a bit erratic ... the hot light is perm on and it wont make ice properly .