a/c repaiedr not replaced
Don't know what is not working on your unit but it could be a broken refrigerant line. You might want to check out a home repair A/C type shop rather than an RV or trailer shop. Several years ago our unit quit blowing cold air while we were traveling. Contacted several shops along the road and they wanted $700 to $800 for the unit plus labor for a new unit as they said the units are cheaper to replace than repair. Checked a couple RV places back home and they gave about the same quotes. Decided to call a friend who does residential A/C work. Found out we had a broken refrigerant line. He repaired the line, installed an evacuation port and filled the line with refrigerant. Still working after 3 years. He only charged $80. Offered some beer as a tip but he doesn't drink. So I gave him a cash tip.
Never hurts to check other sources for repairs. A case of beer would be a lot better than a paying for a new unit!