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Dashboard Vent Air VERY warm

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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

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Bob,

Welcome to the FMCA Forum.

Certainly, the Ford E's have a lot of under-hood heat that will warm the HVAC incoming air.

BUT, It would would not hurt to install an in'-line ball valve in the line to the heater core so you absolutely know that you have no 190 degree water circulating through the heater core.

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Good idea from Brett on the shut off valve. Something else to check, the system is vacuum-driven and the failure point is where the vacuum hose goes through the AC system on the passenger side.  If you look at the vent on the far right side of the passenger side up under the dash, you will see that it is run through the AC system. How to test:  the vacuum line runs from the intake on top of the rear of the motor (red vacuum hose) up and across the front of the engine compartment, to the passenger side, changes to a black hose where it dives into the AC system.  You can test by disconnecting the hose where it changes from red to black, at the top of the engine compartment, just behind the battery.  It is in a notch.  If vacuum is there, reconnect and move to the passenger side.  The black hose comes through the AC with a grommet sealing it.  The line connects to a fitting.  Again with the engine running, see if you have vacuum. Let us know if you have vacuum.

Bill

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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

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The easiest fix is installing the shutoff valve. See if the vacuum is moving the flopper door to give you defrosters. Some systems default to defrost if the vacuum is lost. 3/4 sounds about right for heater hose, but who knows what they used.:o

Bill

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Putting a ball valve would enable you to totally shut off the hot coolant flow to the heater, but it will also shut it off to the defroster. Lots of people do this in bus conversions, and then suddenly find themselves in need of hot air in the defroster, which is not possible till they pull over and manually open the valve. I've had situations more than a few times where a sudden temperature change caused the windshield to fog up quickly, and having the ability to blast it with hot air in a hurry can be a life saver.

If your system is what I'm thinking of, the vacuum system is either going to control a valve in the water flow or possibly a flapper door which diverts the airflow across or around the heater core, depending on the setting at the dash. My suggestion would first be to see if it's something as simple as a vacuum line which has worked loose or possibly a vacuum leak from a split end on a hose or fitting. If you have a flapper door it might have a leaf or other debris in it causing it to not fully close/open.

If you decide to install a manual valve, there are options other than a ball valve under the hood. You can also install a cable-operated valve like I've got in my step van. The inside end looks like an old-fashioned choke knob, and the other end connects to one of these https://www.millsupply.com/cable-controled-water-shut-off-valve-54553.php?p=97521

This solution will require a bit more installation effort, but it will allow you to retain full functionality of the temperature settings from inside the cab year-round. Here's one example of the cable that you'd use inside to control the valve: https://www.millsupply.com/cable-54062.php?p=97809

These valve are available with 5/8" or 3/4" fittings, and they can be ordered with push-to-open or pull-to-open. Install is as simple as cutting the heater hose feeding the heater core and inserting the valve with a couple of clamps. To avoid having to drain the entire system, get yourself a pair of these: https://www.amazon.com/GearWrench-145-Hose-Pinch-Pliers/dp/B000O3NACS/ref=sr_1_7?ie=UTF8&qid=1541627794&sr=8-7&keywords=hose+clamp+pliers The pliers will allow you to pinch off the hose on either side of where the valve is going.

You can also use the pliers to test the hypothesis. Clamp off the heater hose to the heater core and see if the air still blows hot at the dash.

Also, double check to see if the problem is caused by the proximity of an exhaust pipe, exhaust manifold, or other heat-producing item to the air vent. If it's always done this, then that might be what's happening and it would suck to go through the trouble of installing a fix only to still have the problem. If the problem has only come up recently, then this probably wouldn't be the issue.

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Seems to me that most systems have a recirculate setting that would stop cold air going through the system on a bitter ND night for maximum heat or allow maximum cold A/C  on a really hot day in Texas. If your system has that setting and most do ,use that to stop unnecessary  warm air on an otherwise pleasant day.

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32 minutes ago, obedb said:

Seems to me that most systems have a recirculate setting that would stop cold air going through the system on a bitter ND night for maximum heat or allow maximum cold A/C  on a really hot day in Texas. If your system has that setting and most do ,use that to stop unnecessary  warm air on an otherwise pleasant day.

Wouldn't that just close off the outside air from coming in? If there is hot coolant circulating through the heater core it would still be there and still shed heat into the interior of the coach.

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It closes off the ram air from moving over the heater core. When you want maximum cooling you shut off outside air flow over the heater core.  This is not rocket science folks. Spent many miles behind a HVAC system.  They all work the same. During the summer,  older systems required me to turn hot water valves controlling water headed to the heater core off with old fashioned handles. Right is tight/ left is open. Now you can do it with dash board controls.

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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

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