Hello fellow ForeTravelers. I wanted to share some information on replacing the Tempering Valve, (Mixing Valve) on our U320 Aqua Hot. Our U320 is a 98 and I suspect the Tempering Valve had not been replaced for a long time. The valve stopped mixing the water correctly and fortunately the Aqua Hot Model we have allows for a pretty simple valve replacement. Also, I noticed a small Glycol leak on the Return Ball Valve. This leak appears to be the nut below the green shut off, (refer to picture for all details regarding Tempering valve and Return Ball Valve.) Note: when replacing the Tempering Valve, it was stuck and I was not able to unscrew it, even with vice-grips. I called Keith in Nac and suggested that use the vice-grips again and hit the grips with a rubber mallet with a swift hit and it should break the threaded valve loose. It worked!!!! I was able to insert the new valve. I did add some petroleum jelly to the O-ring per his suggestion. Refer to pics for additional visual info.