Community Forums

DrPhil · 02-09-2023, 03:25 PM

Tried searching this forum for terms above, but answers are washed out by a deluge of issues with dual pane windows fogging. My problem windshield fogging due to temperature changes. What dash HVAC and overhead fan settings are folks using to deal with this issue. Tried defrost setting with AC on the dash controls, and it made the issue marginally better. Then I tried the overhead fans, and made the issue scary worse (was moving down road). What works best?

Rev. Roy · 02-10-2023, 11:33 AM

Why are you using the defrost setting with AC on the dash controls? Try using the defrost setting with a little, or a lot, of heat. I have never heard of using the AC with the defroster.

Dennis C. · 02-10-2023, 11:36 AM

AC with the defroster makes sense in humid climates. In dry climates it doesn’t matter much.

twinboat · 02-10-2023, 12:43 PM

Just living in the RV creates a humid environment. I always run the dash A/C on defrost if the windshield gets foggy.

Air conditioners are dehumidifiers.

Mr. T · 02-10-2023, 01:57 PM

If you're talking about the windshield fogging up while you're stationary, Try opening the drivers side window an inch or so. I have a magna shade so that keeps the flies out.

craigd853 · 02-10-2023, 02:14 PM

Quote:

Originally Posted by DrPhil

Tried searching this forum for terms above, but answers are washed out by a deluge of issues with dual pane windows fogging. My problem windshield fogging due to temperature changes. What dash HVAC and overhead fan settings are folks using to deal with this issue. Tried defrost setting with AC on the dash controls, and it made the issue marginally better. Then I tried the overhead fans, and made the issue scary worse (was moving down road). What works best?

Hello sir, make sure that when you are in the defrost mode you are not using the recirculation mode of the A/C. This will cause the issue you are referring to. Also, the front window in most rv's are huge and require a good amount of airflow to keep defrosted. Depending on the temp of your living conditions
behind the seat area this as well could be affecting the defogging of your front window because you stated that you turned your fans overhead on as well. Depending on outside temp and humidity this too has a lot to do with what temp to use when defrosting your window. I know some folks put a sheet up right behind the driver and passenger seats when traveling to help control heat in the driver area during the winter time and the summer time to help keep the immediate area cool. Good luck

RVStitchy · 02-10-2023, 02:33 PM

You should have another switch on the dash for fan. That would be front heat from the Oasis. I recall Zone 1 furnace. Going by memory with the Coach in storage. That same switch helps heat the front of the coach if you are parked at camp and sitting in the driver or passenger seat.

DrPhil · 02-11-2023, 06:43 AM

Quote:

Originally Posted by craigd853

Hello sir, make sure that when you are in the defrost mode you are not using the recirculation mode of the A/C. This will cause the issue you are referring to. Also, the front window in most rv's are huge and require a good amount of airflow to keep defrosted. Depending on the temp of your living conditions
behind the seat area this as well could be affecting the defogging of your front window because you stated that you turned your fans overhead on as well. Depending on outside temp and humidity this too has a lot to do with what temp to use when defrosting your window. I know some folks put a sheet up right behind the driver and passenger seats when traveling to help control heat in the driver area during the winter time and the summer time to help keep the immediate area cool. Good luck

I think I may have had it on recirculate, so that is the likely culprit.
Btw, running AC with heat (and no recirc) would be the most effective way to dehumidify, and if it is a foggy (as opposed to frosted) front window, this makes most sense i think. Thanks everyone!

redbaron73 · 02-11-2023, 09:48 AM

I attempt to keep the interior of the coach at 68F year round. When in humidity, this will obviously cause fogging, depending on temperatures. My method described below is dual purpose: comfort while driving and windshield visibility.

#1 always drive with rooftop air running on desired temperature. Exception is winter driving, then furnace is used.

#2. Always have dash overhead fans running.
This circulates the air, removing the heat buildup from the top and allowing cool air to flow in. During the winter it moves warm air past the window. The goal here is to reduce the temperature difference between house and inside glass *and* remove inside moisture before it occurs.

#3 I then use the dash ac for comfort, on any setting. The defrost from dash air is useless. I only use it if I want cool air delivered to me indirectly.

I will adjust the fan speed overhead based on temps outside or moisture buildup. The goal is to always be ahead of your needs. When I know the outside temps are 95+, I will start with fan on high.

I've been doing this since my Fleetwood discovery. That coach would never keep up with 105F temps
Often the front cab was in excess of 90F even with all air running.

My 3 newmars have always been comfortable, with can temps below 75F, and my wife with a lap blanket.

I never have an issue with fogging when I plan ahead.

DrPhil · 02-11-2023, 01:14 PM

Quote:

Originally Posted by redbaron73

I attempt to keep the interior of the coach at 68F year round. When in humidity, this will obviously cause fogging, depending on temperatures. My method described below is dual purpose: comfort while driving and windshield visibility.

#1 always drive with rooftop air running on desired temperature. Exception is winter driving, then furnace is used.

#2. Always have dash overhead fans running.
This circulates the air, removing the heat buildup from the top and allowing cool air to flow in. During the winter it moves warm air past the window. The goal here is to reduce the temperature difference between house and inside glass *and* remove inside moisture before it occurs.

#3 I then use the dash ac for comfort, on any setting. The defrost from dash air is useless. I only use it if I want cool air delivered to me indirectly.

I will adjust the fan speed overhead based on temps outside or moisture buildup. The goal is to always be ahead of your needs. When I know the outside temps are 95+, I will start with fan on high.

I've been doing this since my Fleetwood discovery. That coach would never keep up with 105F temps
Often the front cab was in excess of 90F even with all air running.

My 3 newmars have always been comfortable, with can temps below 75F, and my wife with a lap blanket.

I never have an issue with fogging when I plan ahead.

Perfect! Exactly what I was looking for!

The Brews Cruise · 02-12-2023, 01:48 PM

Quote:

Originally Posted by Rev. Roy

Why are you using the defrost setting with AC on the dash controls? Try using the defrost setting with a little, or a lot, of heat. I have never heard of using the AC with the defroster.

I live in Florida, and I have for many years used AC on with defrost, and the temp control to heat. The "warm" air absorbs moisture, then moisture is removed by the AC condenser coils. This helps to defog the inside of all the windows in my truck or car. I do the same with our motorhome.

DrPhil · 03-23-2023, 02:26 PM

Just a follow up note. I have taken to running my dash AC with added heat as "The Brews Cruise" recommended above. One does have to plan ahead running it before takeoff like RedBarron suggests, and in doing so, it works like a charm! Thanks everyone!

mahdi · 03-23-2023, 09:45 PM

Quote:

Originally Posted by redbaron73

I attempt to keep the interior of the coach at 68F year round. When in humidity, this will obviously cause fogging, depending on temperatures. My method described below is dual purpose: comfort while driving and windshield visibility.

#1 always drive with rooftop air running on desired temperature. Exception is winter driving, then furnace is used.

#2. Always have dash overhead fans running.
This circulates the air, removing the heat buildup from the top and allowing cool air to flow in. During the winter it moves warm air past the window. The goal here is to reduce the temperature difference between house and inside glass *and* remove inside moisture before it occurs.

#3 I then use the dash ac for comfort, on any setting. The defrost from dash air is useless. I only use it if I want cool air delivered to me indirectly.

I will adjust the fan speed overhead based on temps outside or moisture buildup. The goal is to always be ahead of your needs. When I know the outside temps are 95+, I will start with fan on high.

I've been doing this since my Fleetwood discovery. That coach would never keep up with 105F temps
Often the front cab was in excess of 90F even with all air running.

My 3 newmars have always been comfortable, with can temps below 75F, and my wife with a lap blanket.

I never have an issue with fogging when I plan ahead.

Good plan that I follow most of the time. There are exceptions. Once I was running heat from Oasis and dash, a sudden winter storm with no warning in SD totally fogged the windshield. The reverse happened with the house ACs running in a hard rain storm (Houston style).