Tuesday, July 5, 2022


Ask Dave: Why is a fan blowing air around inside the AC?

Answers to questions about RV Repair and Maintenance from RV expert Dave Solberg, author of the “RV Handbook” and the managing editor of the RV Repair Club. This column appears Monday through Saturday in the RV Travel and RV Daily Tips newsletters. (Sign up for an email reminder for each new issue if you do not already receive one.) Today Dave discusses air conditioner fans.

Dear Dave,
Regarding air conditioners on most RVs with a six-blade fan: The fan is set about halfway into the shroud. When it’s running, I feel air blowing out the side of my unit near the rear of the inlet slots. It seems wasteful to be blowing air around the inside of the AC instead of through the condenser. Shouldn’t most of the blade be located past the shroud? (The picture isn’t mine, but similar.) —Michael

Dear Michael,
The six-blade fan you are referring to is the condenser fan. It is designed to draw outside air in through the rear condenser coil in the AC. This cools the hot coils inside the condenser and blows outside. Here is a photo similar to the one you provided.

How the air conditioner works

Below is a diagram showing how the air conditioner is designed to operate. Warm, moist inside air is pulled up through the air return inside your rig by the squirrel fan that is attached to the other end of the rod with your six-blade fan. This air is drawn over the evaporator coil or fins that have cooling tubes inside. The compressor sends the coolant to the evaporator and it flashes removing heat and moisture. The cool air is then sent back inside the rig by the squirrel fan and is either distributed at the AC unit or through the ductwork on certain models.

Tubes containing the hot liquid that just conditioned the air at the evaporator is routed back through the condenser. Outside air is drawn in from the back to cool it down before going back to the compressor. This outside air never reaches the inside of the rig. Rather, it is diverted out the side at the back, which you are feeling coming from the vents.

Read more from Dave here

Dave Solberg worked at Winnebago for 15 years developing the dealer training program, as marketing manager, and conducting shows. As the owner of Passport Media Creations, Dave has developed several RV dealer training programs, the RV Safety Training program for The Recreation Vehicle Safety and Education Foundation, and the accredited RV Driving Safety program being conducted at rallies and shows around the country. Dave is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.


Here’s a video from RV Repair Club about How Cooling Units Work.


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Thomas D
10 months ago

You miss a line in your drawing ,a vertical line between the motor and fan on the left. It kinda shows the whole thing is a common space. Youd have the hot condenser air and the cool evaporator air mixing. It’d never cool. And if i remember right the air to cool the condenser moves from the side vents past the fan motor and out the back. You wouldn’t want all that hot air adding heat to the fan motor and compressor.

10 months ago

I think you missed what the poster actually said. He was talking about the condenser fan. He stated that it is blowing air out of the side inlet vents as well as the rear outlet. I agree with him that the fan should be totally inside the shroud to maximize air flow through the coils.

Rick Myers
10 months ago
Reply to  Bob

Evaporator Fan

10 months ago
Reply to  Bob

I agree he missed the mark, he usually does. Even his diagram shows the condenser fan pulling air in, which it does not. Spend yer $$$ elsewhere.

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