Joe,
Thanks for the reply. It took a bit of searching, but I found an old post of yours with a picture of the valves on an older coach. By referencing that post, I was able to locate and turn off the two valves connected to the lines that go straight up and then take a 90-degree turn to the front into the coach. Everything worked perfectly after this adjustment. It was a learning experience, but now everything is running smoothly.
The OTR air works well now, and the coach stays cooler longer during stops. Also, I no longer have issues with the water tank overheating. With my solar setup, I don’t need to heat the water tank with coolant while driving.
I appreciate the tip about checking the OTR air filter. I’ll be sure to look into that. The dash air is functioning well.
Regarding the Webasto, I used it briefly last winter but found it consumed diesel too quickly for my taste. I opted for a couple of Dyson space heaters instead. I plan to fire up the Webasto again this winter and run it periodically. Hopefully, running it once a year will be enough to keep it in good condition.
Thanks again for your help!