Hot Air coming through dash vents when AC selected.

[rvcarpenter]

HI,
I have a 2001 Itasca 30w on a workhourse chassis. I have this problem with the dash AC / heater controls no matter how I set the temperature (on my rig a little slide level on the dash just like any GM car for the last century) I always get hot air coming out the vents. Dosen't matter whether I choose defrost or heater or vents, always hot air. Now I have just been turning all the dash controls off and using the house air and we are very comfortable but I would like to fix it.

I assume it's some connection from that slide bar to something. so what I'm asking when I get in the dash what should I be looking for? Vacum tube, a cable or what? Anyone else ever have this problem? In the end I want to fix it myself so any advance would be welcome.

Thanks

[rvcarpenter]

HI,
I have a 2001 Itasca 30w on a workhourse chassis. I have this problem with the dash AC / heater controls no matter how I set the temperature (on my rig a little slide level on the dash just like any GM car for the last century) I always get hot air coming out the vents. Dosen't matter whether I choose defrost or heater or vents, always hot air. Now I have just been turning all the dash controls off and using the house air and we are very comfortable but I would like to fix it.

I assume it's some connection from that slide bar to something. so what I'm asking when I get in the dash what should I be looking for? Vacum tube, a cable or what? Anyone else ever have this problem? In the end I want to fix it myself so any advance would be welcome.

Thanks

["007"]

Hi, your looking for a vacum line to a valve on your heater hose behind AC/Heater unit. The hot water is going thru the heater core defeating your AC cooling. You can get a new Evans valve or like I did place a plumbing ball valve connected to your heater hose to shut off that hot water. I did this before we went to Branson rally and we were running cool from Evans AC. Did find though that hot water will also backup from other hose so I'm going to place a second ball valve in other heater hose.
Just remember to open valves during winter months or your going to freeze like this summer.

[rvcarpenter]

thanks 007 I will look for a vacum line disconnected or with a hole in it or some such thing.

["007"]

Yes look for the simple thing first you will see the vac line going to valve. If its ok, to test valve you can take some vice grip pliers and squeeze the hose to see if shutting of hot water the AC cooling improves.
Some reading on this LINK.

[skigramp]

Our first motorhome was used ... when it was new there was no by-pass on the hot water heater for winterization ...

The previous owner bought three valves, two T's and a short piece of connection hose. Next to the input he installed a shut off valve ... in front of that a T ... he did the same on the output side ... and between the two t's he installed the third shut-off.

For normal operation the input / output valves were open and the middle valve was closed ... for bypass operation the input / output valves were closed and the middle valve was open ...

Perhaps you could do the same with your heater hoses ...

{Note: this was an older model ... there was no check valve on the hot water heater}

[Don-Savannah, GA]

My info is based on a Ford chassis, don't know about Workhorse.
I agree, the first thing to check is vacuum to the heater valve inside the engine compartment, unless it is a cable coming from your slide lever on the control panel. Next check the vacuum going to the outside air intake control valve, you should hear it moving when you switch to and from Max A/C.
I had a similiar problem on mine so I installed a manual bypass valve, it did not help. I confirmed that the vacuum valve on the outside heater box was closing on Max A/C.
I finally realized it was only happening when I was stopped or going slow, although it did not happen when the A/C was on Max. The Max position recirculates air from the coach, no outside air. That made me believe that the heat from the front of the radiator was being sucked up into the outside air intake when stopped or going slow.
I always switch to Max when entering a slow zone.

[bruceh]

I have a 2001 Winnebago 35U on the Workhorse chassis and had similar issues. You don't mention whether this happens all the time or just when you are stopped.

Mine occurs when I am stopped and (after a lot of jerking around) was informed that this is 'normal behavior'. The pickup for the ventilation system is under the hood and when stopped sucks hot air.

Don't know if this is your problem but it's worth considering

["007"]

bruceh welcome to the forum.
The heat is coming from the hot water in the radiator that is getting by the Evans control valve for cooling, it with time has found to be faulty. Either replace with new valve or place plumbing ball valves in hot water line so AC is not fighting the hot water in heater unit part of EVANS AC/HEATER unit to cool your coach down.
Enjoy the forums and do post often.
Thanks for posting your first post and joining in.

[inphx]

i have 05 workhorse chassis. I live in Phoenix AZ. I had similar problem. the answer I got was expect this in city driving in the summer. Normal unless you put in auxiliary radiator. On the highway the system works fine.

[MikeT]

Air pickup is under hood facing down, and will pick up under hood heat. Max AC will recirculate cabin air and cool a little better. Certain Winnies do not use the Evans system. My Voyage dash air leaves a lot to be desired. Outlet temps are too high as compared to automotive units. I'm not sure if the condenser or evaporator are the problem, but it just doesn't do a good job of cooling. My duct temps don't vary between start up or hard run, so heater core heat doesn't enter into my problem.

[rvcarpenter]

The air is hot all the time whether it's in the city or on the highway. I've pretty much given up on it. I'll just run the house AC when I need it. Luckly I don't travel in hot weather very much.