I have a 2000 Lincoln LS, V8, and I have an intermittent problem in the summer with the AC. Two dealers and an independent mechanic could not figure it out. After a period of time when running the AC, heat comes out of the passenger side air vent and AC out of the driver side air vent. Eventually, if I run it long enough, the driver’s side air vent will also produce heat. This usually occurs on a very hot day. I do not have a problem with the heat during the winter. I know this is a persistent problem with the LS because I have seen the dialogue on the web, but I have not come across anyone who has solved it. Any thoughts?
It’s a common problem, and is easily solved. You need to replace your DCCV (Dual Coolant Control Valve). It’s about a $150 part, should be around $300 if you have someone replace it. The coolant should be flushed too, unless you have done so in the last three years or less.