My SIL just bought a used 5th wheel. When she recently went to turn on the heat she noticed immediately that the heat AND the a/c came on together and they were both blowing from the vents in the roof....no heat coming out of anything near the floor!What would cause something like this to happen and has it happened to anyone else? Where should she begin to look to figure out what is going on here?

My new FW will allow me to set the heat and AC at the same time. The theory is that if you were to be away all day and it's cold in the am but hot in the afternoon, the heat can run to bring it to temp X and the AC to temp Y. If the temps were set to be the same, I guess it's possible they could both come on at the same time since they are independent systems. They don't use the same ducts however. I guess questions would be how did she know both were on ? Was there a panel that told her this? And how did she know they both came out of the same duct? Does she have a heat pump in her AC unit? It is possible that the ducts could have held hot air when the AC turned on and felt warm until the ducts cooled?

How can you both heat and cold from the same vent? LOL. See the above last line/

1. Need Brand and Year Model of RV and Brand Model of AC and type wall tstat. Without this info nobody can help you.2. ODDS are she is NOT activating the Heat(furnace) at all. She is activating the Roof AC system and is seeing the air blowing out the roof vents.3. Depending on the Brand and Model AC and tstat, Dometic's on some units, if you DO NOT have the roof AC Fan set to AUTO, the Roof AC fan will come ON when you activate the floor LP furnace. That is normal on this type system. But the furnace should still come on and blow out the Floor vents. Doug

Perhaps it's like mine. My T-sat has a selection for 'Furnace' and in that case the furnace will come on and blow out of the lower furnace ducts. Also, I can select 'Auto' and in that case if the T-stat calls for heat the AC comes on and works as a heat pump blowing warm air out the upper AC ducts. If the trailer is warmer than the set temperature the AC blows cold air out of the same upper duct.

Sounds like you have a heat strip inside the AC unit. Some AC units will do cold or hot.

Heat & A/C on at the same time! | Good Sam Community

jdc1
Explorer II
Sep 17, 2020
How can you both heat and cold from the same vent? LOL. See the above last line/
way2roll
Navigator II
Sep 17, 2020
My new FW will allow me to set the heat and AC at the same time. The theory is that if you were to be away all day and it's cold in the am but hot in the afternoon, the heat can run to bring it to temp X and the AC to temp Y. If the temps were set to be the same, I guess it's possible they could both come on at the same time since they are independent systems. They don't use the same ducts however.

I guess questions would be how did she know both were on ? Was there a panel that told her this? And how did she know they both came out of the same duct? Does she have a heat pump in her AC unit?

It is possible that the ducts could have held hot air when the AC turned on and felt warm until the ducts cooled?

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Heat & A/C on at the same time!

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