Dash vents blow hot air under heavy engine load? - Page 2

Bones2003 · 01-20-2021, 08:45 PM

Thanks Bobby. Yeah, that 3 port Victory Climate Systems water valve is my prime suspect at this point. It is an electric valve (motor driven) that only has 3 wires going to it. +12 V power, ground, and a control voltage that comes from the temperature control potentiometer on the dash HVAC control panel. I haven't been able to measure the control voltage yet to see what voltage opens the valve and what closes it. As a first step, I plan to just disconnect that 3 pin connector from the 3-port valve and see if it defaults to open or closed. It may just stay wherever it was last set. If it defaults to closed (i.e. no hot to heater coil), I plan to drive it to see if hot air starts to blow out the vents when under load.

Edit: I know the valve functions ok when not under load. When the HVAC control knob is set in the blue area for cool - it blows cool air. When the HVAC knob is set in the red area for heat - it blows hot air.

1237dmctlc · 01-21-2021, 08:40 AM

You seem to be knowledgeable and have vetted a lot of the possible source of the problem as well as solutions. I understand the need to learn your MH, I'm the same way, but why not bring it back to either your dealer or better yet to a local Ford Truck dealership to fix the repair or at least call them and see what they say? Have you checked to see if there's any TSB's out for this issue? Being under warranty why not let them fix it or is it in a place that makes it difficult to get it out? Or are you concerned being winter they won't be able to mimic the issue? If it turns out that it's the 3 way valve is it you intention to replace it yourself or at that time bring it back at that time? IMHO problems like this I prefer to let the warranty work for me to avoid any pushback if they claim I initiated the problem or made it worse but trying to confirm the source of it.

Bones2003 · 01-21-2021, 10:42 AM

Thanks Dana - I appreciate your comments. I am pretty sure Ford would point the finger at Winnebago since the only Ford parts of the dash HVAC system are the AC compressor and condenser (plus a couple of hoses) - as far as I can figure out anyway. The entire rest of the dash HVAC system is Winnebago so it would be a dealer item. Mostly, I'm just thinking about the problems and possible solutions but I may do some checks in a very low impact way so that I don't void the warranty.

I'm working on my list of dealer warranty repair items so that I can hopefully go in once to get everything resolved. So far, the list is very small but I haven't been able to check out every system due to the cold weather. I may instead take it to the Winnebago factory depending on the list.

eaglelen · 01-24-2021, 07:30 AM

I am having a heater problem - no heat! I have a leftover 2019 Adventurer 35F on the f53 chassis. First winter, drove to the dealer for some warranty work, and no heat! Dealer says it's a ford issue - part of their chassis. Any clues?

Bones2003 · 01-24-2021, 07:56 AM

Quote:

Originally Posted by eaglelen

I am having a heater problem - no heat! I have a leftover 2019 Adventurer 35F on the f53 chassis. First winter, drove to the dealer for some warranty work, and no heat! Dealer says it's a ford issue - part of their chassis. Any clues?

Len, since you have a different problem than what I originally posted on this thread, I recommend you create a new thread specifically for your problem. That way you will get the most help.

1237dmctlc · 01-24-2021, 08:01 AM

Quote:

Originally Posted by Bones2003

Len, since you have a different problem than what I originally posted on this thread, I recommend you create a new thread specifically for your problem. That way you will get the most help.

I have to agree then in the future if you're looking for that thread or post you'll find it easier because it will show up in your profile under those titles.

Bobn1957 · 03-14-2021, 03:30 PM

Quote:

Originally Posted by Bones2003

Hi Morich, thanks for your idea but I'm pretty sure that is not the situation. I was driving 55 MPH at 2000 RPM with AC off and cool outside air blowing through the vents. For every hill I encountered, the transmission would downshift, the RPM would jump up to 3500 or so, the speed would maintain at 55 MPH but then hot air would start to blow out of the vents. Once I topped the hill, RPM drops back to 2000, transmission upshifts, and cool air starts to blow out of the vents again. It happens consistently and fairly quickly (although not instantaneously). These were not huge mountains but the hills around Springfield, MO so climbing them would only take a few minutes usually. Hard to envision air flow off the engine doing that. Like I said, it blows cool (as expected) except under load.

Under load at those RPMs there is less vacuum to control the heater, I think you have a vacuum leak somewhere that's bleeding off vacuum and opening the heater coolant valve.

Bones2003 · 03-14-2021, 08:08 PM

Quote:

Originally Posted by Bobn1957

Under load at those RPMs there is less vacuum to control the heater, I think you have a vacuum leak somewhere that's bleeding off vacuum and opening the heater coolant valve.

Thanks Bobn1957, but as I said above in several posts in this thread that my 3-way heater coolant valve is not at all vacuum operated. It is an electric actuator controlled by a potentiometer in the dash heat/AC control panel. As far as I've been able to determine, vacuum is not involved anywhere in the system. Is there some interaction with engine vacuum that I am missing?

Wyatt · 03-14-2021, 09:38 PM

Ok, this may be way off base, but we had a similar issue with our air, in that at higher RPM’s, the evaporator would build up too much pressure and, as a safety protocol, it’s designed to drop back down in pressure. Maybe your issue has nothing to do with hills, but just that’s when you notice it—with higher rpms.
So in our case, warm air would come out at higher rpms, and at low rpms the air was cool. Have you checked the air coolant level? I’d take it in to have it tested as I did ours. Once hooked up to their charger, we found the issue. Our coolant level was fine, but the evaporator was bad. I have a video of it if you want to see the gauge fluctuations under various rpms. Can you hear the clutch going on and off when this happens, or is it too noisy?

Bones2003 · 03-15-2021, 10:52 AM

Wyatt, are you talking about high pressure in the dash air conditioner evaporator or in the heater core? My problem with excess dash heat at high RPMs happens when the dash air conditioner is off. Will the symptoms you described with high evaporator pressure happen with the dash AC off?

Wyatt · 03-15-2021, 01:21 PM

I was talking about the evaporator for the AC. Sorry to confuse the issue. This thread has gotten pretty long and I guess I somehow lost track of your original issue.

Hermes2 · 03-25-2021, 10:51 AM

Quote:

Originally Posted by Bones2003

Any thoughts on what would cause the dash air vents to suddenly start blowing hot air when the engine is under heavy load/high RPM (such as climbing a hill)?

With the temp control knob set all the way to cool, the vents blow cool air as you would expect when driving on a flat highway at about 2000 RPM. Once the RPM drops back to 2000 again after the hill, the vents slowly start to blow cool air again. This is on a 2021 Winnebago Vista 35U with the new Ford 8 cylinder engine. It acts just like the old vacuum controlled dash heat/AC/vent/defrost systems when they had a vacuum leak. As far as I can tell, this version of the Vista uses all electric motors to control the blend/mix doors and doesn't use any vacuum actuators or motors. I think the supplier of the dash heat/AC/vent/defrost system is Victory.

Since it is too cold outside, I haven't done any poking around or looking at the system. I have just been doing a little internet searching and thinking about it. The internet searches came up with lots of complaints about the vacuum systems. In fact, I had the vacuum leaks that I fixed on my previous 2003 Winnebago Sunova. Thanks in advance for your ideas.

We have the exact same problem on our new 2021 Adventurer 29B. I'm looking forward to any resolution, as we are planning a trip out to western Utah in May/June. I plan on contacting Winnebago and Ford regarding this.

Bobn1957 · 03-25-2021, 12:35 PM

I had the same symptoms last fall where under load the dash vents were pumping out hot air when the coach was under load. I'm leaning towards the fresh air inlet and determining its location. If the inlet is in the engine bay that would be the culprit because under load the engine increases the temperature in the engine bay. If I find that this is true I will duct the inlet out in front of the radiator.

Mickey_Z · 05-20-2021, 04:54 PM

I have nearly the same issue on a 2021 Winnebago Vista 27N. It’s been to the Dealer (3) times. Twice in Florida and once in Michigan along with once at the Ford dealer.
The AC works at idle, above about 30 mph it’s starts blowing warm/ hot air. This is on vent, ac, recirc or no recirc. It seems like the AC can’t override the hot air stream even at 45 degree ambient. So far they lowered the Freon pressure, replaced the expansion valve and replaced the 3 way water flow valve. As was mentioned the air flow box is controlled by electric solenoids. It’s currently in the dealer (3 weeks) and they are now working with Winnebago direct. No answer yet, but once I find out I will update. It seems like it has to be related to the water flow through the 3 way valve, either a backflow or leakage issue.

Mickey_Z · 05-27-2021, 10:50 AM

Just got my 2021 Vista back from the dealer. I had to call Winnebago direct and connect them to the dealer to get this resolved. After 3 fixes mentioned in previous post issue was found with coolant lines on new 7.3L. Evidently Input/Output are reversed compared to previous 6.8L and are connected to coolant 3 way valve feeding AC unit. Probably many units with this issue. I'm attaching pics of the hose routing that solved this issue. My dealer says there is a TSB from Winnebago forthcoming.

Morich · 05-27-2021, 11:35 AM

So we now know it is true! They put things together without reading the directions and nobody actually stops to THINK when it doesn't work! DUH!

Wyatt · 05-27-2021, 12:41 PM

Well that’s embarrassing…

Bones2003 · 05-28-2021, 07:08 PM

Quote:

Originally Posted by Mickey_Z

Just got my 2021 Vista back from the dealer. I had to call Winnebago direct and connect them to the dealer to get this resolved. After 3 fixes mentioned in previous post issue was found with coolant lines on new 7.3L. Evidently Input/Output are reversed compared to previous 6.8L and are connected to coolant 3 way valve feeding AC unit. Probably many units with this issue. I'm attaching pics of the hose routing that solved this issue. My dealer says there is a TSB from Winnebago forthcoming.

Mickey_Z, that was my exact problem. I determined the hoses were reversed a couple of months ago and swapped them at that time. I was not able to perform a real test until the past two weeks when we travelled from Kansas City area to Colorado and had lots of hills to test it out. The problem was fixed! I only hope now that the pressure differential caused by the reversed hoses did not weaken the 3-port water valve. If anyone gets a copy of the new TSB, please post it for everyone.

Sorry, it took so long to update everyone, but as you know there are not a lot of big hills in Kansas for me to test out my fix!

Jim_HiTek · 05-29-2021, 12:17 PM

Not sure if this has been mentioned but that air actuated water flow cutoff isn't all that efficient so when the water pressure from the engine goes a bit higher, it forces it's way into the heater core even when the temp is set all the way blue.

What many diesel RV'ers do is add a bypass circuit to the water hoses so during the summer they just reroute the hot water around the heater core. Would probably work in your situation too. Oh, another thing, diesel engines usually have a nice brass water shut off valve at the engine because of those long hose runs in a pusher and we can shut off the water there too. For a front mounted gas engine, I doubt that they added those but wouldn't hurt to look.

For testing, just use a clamp or pair of vise grips to choke off the water at the input hose to the heater core.

Bones2003 · 05-29-2021, 03:56 PM

Quote:

Originally Posted by Jim_HiTek

Not sure if this has been mentioned but that air actuated water flow cutoff isn't all that efficient so when the water pressure from the engine goes a bit higher, it forces it's way into the heater core even when the temp is set all the way blue.

Jim_HiTek, I think all of the motorhomes being discussed here have a water cutoff that is actuated by an electric motor and are not air actuated. Do you think the electric water valves have the same efficiency problem?