Rmendes1

Thanks again to each of you for your insights and suggestions. 🙂 Bob

Brett, Bill and Richard, I'm delighted to report that I installed the shutoff valve for the hot water to the heater core (the one Richard had suggested), and it solved the problem!! I then installed a cable trough the fire wall and mounted it under the dash so that I can control the valve any time while I'm driving. It works great and I'm really looking forward to my next trip! I've essentially been driving with the heat on in my RV for 5+ years. I've attached a few pics of the finished product. Sorry for the long delay in my response. Between caring for a very sick older Golden Retriever I haven't had much time to do the work and then to provide this update. Thanks again to all of you for taking an interest in my dilemma. Bob

Richard, thanks for the terrific insights. All of you, I can't tell you how much I appreciate your help with this persistent challenge. Bill, after your comments about testing the vacuum system I decided to purchase and download a repair manual for the E-450 Super Duty and I now have a MUCH better understanding of how the vacuum system and various air flow settings are supposed to work. I'm looking forward to further evaluating it tomorrow to see if I'm able to determine if there is a problem in the vacuum system and/or hot water leaking past the valve to the heater core. One aspect of my recollection may be incorrect. Now that I understand the airflow with the "Floor" selection, if the air coming through the floor vent is cooler than the air coming through the dash on the "Vent" setting with the temp setting on cold, I think I have my answer in that if the air coming through the floor vent is cool I can essentially rule out hot water reaching the heater core. There may still be a vacuum problem if the recirculation air duct door isn't working properly, but if my understanding is correct then more than likely the hot air coming through the dash vents simply means the air is being warmed up from hot air emanating from the engine and the doghouse. So I'm hoping that the floor air is also very warm as that will lead me to more highly suspect a problem with the inline valve to the heater core. Even if there isn't a problem with the heater valve, I'm inclined to install a manual valve per Richard's suggestion. In any case, I'll report back after I'm completed my further investigation. Thanks again! Bob

Brett and Bill, thank you both for your very helpful suggestions. Bill, I'll test the vacuum lines tomorrow per your directions and let you know what I find out. Unfortunately, I store the RV about a half hour from where I live and today one of my dogs is seeing a surgeon so that takes precedent. 🙂 Assuming I do have vacuum, does that imply the internal valve that prevents hot water from circulating through the heater core is working properly, or is it possible that, as Brett suggests, hot water from the engine may still be leaking past that valve? If so, I'm not sure how I would test that but Brett's suggestion would take care of it. I just need to figure out which hose is the hot water "intake" and then put a ball valve inline between it and the heater core, right? Do either of you know what size hose (and thus what size valve) that is? If I'm looking at the correct hose, it appears to be about a 3/4" diameter. Again, thank you both for your insight and advice, and your very prompt responses! Bob

Hi everyone. I'd appreciate any feedback on this topic, even if you can tell me that you have a similar class C and DON'T have this problem as the dealer told me there isn't anything that can be done as this problem is true of all class C's, which I find hard to believe. I have a 2007 Jayco 30' Class C on a Ford E-450 chassis with a 6.8L V10 engine. Once the engine warms up and I have the dashboard air selector on the vent setting, the air coming out of the vents becomes quite warm. When I change the selector to A/C I get appropriately cold air, and the other settings (e.g. defrost) also work fine, so I'm assuming it isn't a vacuum problem (but I may be wrong about that). The air gets so warm while I'm driving that the cabin gets quite uncomfortable and I have to put the A/C on. The service department at the local Ford dealership never bothered to investigate this issue and suggested that I should simply select the "floor" or "mixed" settings when I'm driving, which does provide cooler air but of course that air doesn't come out of the dashboard vents. After running the A/C until the cabin is comfortable, I then switch the selector back to the vent setting. The air is then initially cool but it once again gradually becomes too warm and I have to put the A/C back on. I bought my RV used in 2010 with 3,500 miles on it. I don't recall this being a problem initially so I have to assume something is wrong. I'm at the point that I'm ready to try modifying the air intake to the vent but before doing so I thought it was worth seeing if anyone else has had this problem and/or if you have any suggestions. Appreciate any advice you can provide, even if you simply tell me you have a similar class C and don't have this problem. Thanks!! Bob in Boulder, CO