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Replacement Exterior Half-Moon Trailer Vent for 3" Diameter Hole - White

Replacement Exterior Half-Moon Trailer Vent for 3" Diameter Hole - White

Item # WHMAV2
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This half-moon-shape vent forms the exterior part of the Alliance 2-piece enclosed trailer vent. Constructed of UV-resistant polypropylene plastic that holds up to sun exposure. White color. 1-636-306-4830 to order Redline accessories and parts part number WHMAV2 or order online at Free expert support on all Redline products. Guaranteed Lowest Price and Fastest Shipping for Replacement Exterior Half-Moon Trailer Vent for 3" Diameter Hole - White. Accessories and Parts reviews from real customers.
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  • Reviews (14)
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  • Videos (2)
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Redline Accessories and Parts - WHMAV2

  • RV Vents and Fans
  • Wall Vent
  • Redline

This half-moon-shape vent forms the exterior part of the Alliance 2-piece enclosed trailer vent. Constructed of UV-resistant polypropylene plastic that holds up to sun exposure. White color.


  • Exterior vent is the outside part of the Alliance 2-Piece Polypropylene Trailer Vent for 3" Diameter Hole
    • Fits round interior trailer vent (WAVT2; sold separately)
  • Half-moon piece with flat, slotted side attaches to trailer's exterior
    • Slots are on one side only, allowing you to position the vent for best airflow and to help prevent water from getting in
    • Drain holes at the corners let out any water that does get in
  • UV-resistant, polypropylene plastic construction stands up to the elements
  • White color
  • Overall dimensions: 8" long x 6" wide x 1-1/4" tall
  • Flange width: 1/2"
  • 6 Screws (sold separately) required for installation
    • Hole diameter: 3/16" (fits #8 screw)
  • Sealant sold separately

WHMAV2 Alliance Outside Half of 2-Piece Enclosed Trailer Vent - UV Resistant Polypropylene Plastic - White

Video of Replacement Exterior Half-Moon Trailer Vent for 3" Diameter Hole - White

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Redline 2-Piece Polypropylene Trailer Vent Review and Installation

Jake: Hey guys, it's Jake here with etrailer. Today we're going to be taking a look at the Redline half-moon trailer vent. This is going to allow fresh air to get in and hot air to get out without having to worry about getting any water inside your trailer.In this kit, you are going to get the outside vent and the inside receiver so that you can have a nice clean look on the inside of your trailer. This is really going to be important for if you have a wall inside your trailer like we do, but if you don't have a wall, you can just use this part and you'll be able to mount it to the outside of your trailer and get fresh air without having to worry about any water.So you can buy these as a kit or you can buy them separately. Now here you'll see we have our vent in black. It's also available in white if you'd like to match it to your white trailer.Here's that piece on the inside wall that we we're talking about.

This is going to give it a nice clean look so you just don't have an open hole in your wall. It's going to have a nice flush mount design so you don't have to worry about anything running into it when it's on the wall. It's also going to help preserve this part from being damaged.If you want more of a cross-flow to go into your trailer, you could pick up a couple of these vents to be able to put one on the opposite corner of your trailer so that you have wind coming in the front and going out the back. When using two vents, it's going to provide a way for cool air to get in and warm air to get out. Now that we've gone over some of those features, let's go ahead and show you how we got it installed.We'll start by drilling a 3" hole.

We're going to start on the inside so that we know we're not going to run into anything inside the walls. You can see we have our ribs here and here, so we're going to split the difference and do it in the middle of them. Then we're going to continue with the hole saw through the sheet metal on the outside so we know where our hole needs to be drilled. We'll go ahead and insert our pilot bit into the hole that we punctured through the sheet metal and start drilling out our hole.I'm going to go ahead and insert our vent on the inside and fasten it down. Here we just found some stainless steel screws so we don't have to worry about any rust.

Now we can move to the outside, and we can go ahead and get our outside vent in place, slide it over. We'll use a self-tapping screw, but you want to be careful with this sheet metal on the outside of your trailer. It's not very thick. You don't want to strip it out. We'll stop right there and hand-tighten from here.

Now we'll go ahead and get the other five screws in place.Now, we went ahead and put some of this Loctite black silicon gasket on the inside. We took our cover off and put it on the inside to seal it up nice and neat to make it a nice watertight seal. We do have this at etrailer. You can pick some up if you'd like.Once you have all your screws in place, you're ready to hit the road.With all that being said, that's going to do it for our look and installation of the Redline half-moon trailer vent.

Customer Reviews

Replacement Exterior Half-Moon Trailer Vent for 3" Diameter Hole - White - WHMAV2

Average Customer Rating:  4.9 out of 5 stars   (14 Customer Reviews)

This half-moon-shape vent forms the exterior part of the Alliance 2-piece enclosed trailer vent. Constructed of UV-resistant polypropylene plastic that holds up to sun exposure. White color.


Product as described .
Install yesterday
on my sprinter van.
Although white in color turns into a oven during the day . so I installed the vents up high on the back side corners.
when I leave a job and vehicle is hot inside I crack the front windows and the vents naturally vacuum the hot air out , until the AC catches up.
Thanks , happy with product and as described.


Arrived exactly as described and on time. Customer service is second to none. Every purchase I've made has been handled with courtesy; every question answered thoroughly and correctly

Actually did not use it, but glad I had it in case I did need it. I stand by my original review All the other items order from etrailer for my solar installation are working great.
David W - 02/20/2021


Had item. Good price. Prompt delivery.


This site is great, always great customer service if there is a questions. Parts come out in an timely manner.


Exact replacement for the vent cover on my trailer. Same shape/holes, etc. Saved time and money. Just remove the broken cover and install the new one.


It's great having a company that stocks trailer parts like these. Had a blowout on my trailer, tire took vent off. Exact match!!! Thanks!!!


Was very happy to find this part of the vent that we needed, easy ordering online and superb customer service. I will definitely be back for more parts!


Great customer support, service and product selection. The only online retailer that sends me follow-up emails. Much appreciated!


Very satisfied with the purchases. All installed and functioning well.


Product came as advertised, on-time in good condition.


Great company to work with and great service too!





See what our Experts say about this Redline Accessories and Parts

  • How To Install the Redline Trailer Vent # WHMAV2-WAVT2 on an Enclosed Trailer
    I do not have an installation video on the Redline Trailer Vent, part # WHMAV2-WAVT2, but I can help you with the installation. The tools you will need are a caulk gun, drill, a 3-inch hole saw, a 3/16-inch drill bit, and a flat-tip screwdriver. The other parts you will need I have listed below in the instructions. The # WHMAV2-WAVT2 vent is two pieces. The # WAVT2 is the 3 inch round interior vent that will need to be installed in a 3 inch diameter hole on your trailer. You will need...
    view full answer...
  • Is There Recommended Hardware to Install Half-Moon Vent on a Fiberglass Box Truck
    Since vents like the Replacement Exterior Half-Moon Trailer Vent # WHMAV2 are for a universal application we don't really have recommended hardware as each installation will be different. From what I could find online it looked like steel screws would be best and you would want to drill into the fiberglass first and then put some sealant like part # 0160297 on the threads of the screws before installing them. I would do some research on your end of things and maybe contact the manufacturer...
    view full answer...
  • Vent Solution for Trailer Tongue Box that Holds In Moisture
    That is really strange and would indicate that your box is holding in condensation and not allowing it to vent out. The part # WHMAV2 would be a great solution to allow it to vent and prevent the moisture as long gas you sealed it up with a sealant like # 0160297 and had it face down.
    view full answer...
  • Vent for Transporting Poultry in an Enclosed Trailer
    I can't tell you for sure how much ventilation you need to transport your poultry because it's really out of my wheelhouse. With that being said using the Trailer Vent # WHMAV2-WAVT2 is a very viable solution. We often see vents like this installed on the side of enclosed trailer towards the front with open side facing forwards and then another of the vents towards the rear of the trailer facing backwards. The idea is to create a pass through of air flow.
    view full answer...
  • Can the Polypropylene Trailer Vent Be Trimmed to Fit Thin Trailer Walls
    If you find that the wall of your trailer is too thin then you would have to trim at least one of the pieces to allow for a secure fit but make sure it is a straight cut and not an angle cut. Otherwise it may not fit properly together.. ideally you would want a little wiggle room to adjust it as needed without leaving too much of a gap. As for the positioning I would have blades facing down so it is harder for moisture to get in.
    view full answer...
  • Would the 2-Piece Polypropylene Trailer Vent # WHMAV2-WAVT2 fit a 2 in Thick Wall
    Yes it will, the 2-Piece Polypropylene Trailer Vent # WHMAV2-WAVT2 that you referenced would work on a 2 inch thick wall. You would just need to cut a 3 inch diameter circle hole in that wall and attach either side of the # WHMAV2-WAVT2 and it would function just fine.
    view full answer...
  • Vent Positioning for Trailer Vent # WHMAV2-WAVT2 to Prevent Rain/Exhaust from Getting in Trailer
    To keep exhaust out of the # WHMAV2-WAVT2 you will need to install the vent higher on the trailer than the exhaust preferable on the side of the trailer. The further back on the trailer the less chance you would have for exhaust to get in. Having the vent point down or to the rear of the trailer will also prevent rain from getting in the trailer while traveling down the road. This will allow the vent to function more as an exhaust vent. We have several customers who have installed the...
    view full answer...
  • How Does the Half Moon Vent # WHMAV2-WAVT2 Install
    The vent uses a 3 inch diameter hole in the trailer. The half moon portion is flush mounted to the outside of the trailer. It is not necessary to cut any holes in the vent. The interior trim piece is deep enough that it will pass through the trailer wall and mate up with the raised circular portion of the outside half-moon portion. The part is also available in black, as part # HMAV2-AVT2. I have edited a photo of this vent in black so that you can more easily see how the vent goes together.
    view full answer...
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  • Which Way Should 2-Piece Polypropylene Trailer Vent be Placed
    If it were me I would install the trailer vent # WHMAV2-WAVT2 with the fins angled down to reduce the amount of rain that could fall into the vent. Having it at the front of the trailer should be fine since the tow vehicle is going to act as a screen for a large portion of the wind. Also, most trailer tires are not rated for speeds over 65 miles per hour so you will want to keep an eye on that! If you want air flow-through then you would want one vent at the front and another at the back....
    view full answer...
  • Availaiblity of White Half Moon Trailer Vent
    We do have the white Replacement Exterior Half-Moon Trailer Vent for 3" Diameter Hole # WHMAV2 which is the white version of the # HMAV2 that you referenced and also is what you sent in a picture of so it would work well for you.
    view full answer...
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  • Can PVC Be Added To Install the 2-Piece Polypropylene Trailer Vent On a Thicker Wall
    In regards to the 2-Piece Polypropylene Trailer Vent part # WHMAV2-WAVT2, I must recommend you install the vent using both the inside and outside components. If the wall thickness is too much to use the vent as is, all you will need to do is take a piece of PVC to bridge the two together. I have attached for you below a review on a customer who did the same. I checked with Redline and they don't offer the specific measurements you are looking for unfortunately.
    view full answer...
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  • Side Vent for Enclosed Trailer with Interior Wood Paneling
    You can still use butterfly vent # 371800. The wood paneling in the trailer should not be an issue because no matter what material is on the inside you would have to cut a hole for the vent. If there is a gap between the outer and inner walls of the trailer then you could bridge that gap with some small gauge sheet metal such as tubing used for clothes driers. A vent such as # WHMAV2-WAVT2 might be a better option. I have linked a video review of this vent and the butterfly vent as well. I...
    view full answer...
  • How Should the 2-Piece Polypropylene Trailer Vent be Positioned when Installing
    On the 2-Piece Polypropylene Trailer Vent, # WHMAV2-WAVT2, I would mount it near the top front of the trailer with the vent openings pointed down or towards the rear of the trailer. Ultimately, it does not really matter. Use some self-tapping screws like # 31071 and some sealant like # 0160297 when installing the vent.
    view full answer...
  • Vent Recommendation for Storage Box on Trailer to Reduce Condensation
    If you installed the 2-Piece Polypropylene Trailer Vent # WHMAV2-WAVT2 on your storage box with the half circle portion on the outside of it facing down it would be pretty hard for rain water to get in the box. Especially if you sealed it with a # 344270KITW as you installed it. I attached a review video for you to check out as well.
    view full answer...
  • Recommended Sidewall Trailer Vent for Cargo Trailer
    A 3" diameter vent hole is very common for enclosed trailers. I suggest you first completely remove old vent material and measure the opening. If you do have a 3" diameter hole, my recommendation is the 2-Piece Polypropylene Trailer Vent for 3" vent holes, # HMAV2-AVT2. This 2-piece vent provides a great way to ventilate your enclosed trailer. The round interior vent along with the half-moon-shape exterior piece are both constructed of black, UV-resistant polypropylene plastic that holds...
    view full answer...
  • Recommended Wall Vent for Enclosed Trailer with Gas Water Heater
    I recommend our Redline 2-Piece Polypropylene Trailer Vent # WHMAV2-WAVT2. This wall vent will work on a trailer wall up to 2 inches thick and can be installed in any convenient location on your enclosed trailer where you have or can make a 3-inch diameter hole. This wall vent is designed to provide a constant flow of air, and is louvered on one side so you can adjust it when installing for the best airflow and to help prevent water from getting in. You can use a sealant for installation...
    view full answer...
  • White Side Wall Vent For Enclosed Trailer With Refrigerator
    I do have an option for you but the Mushroom Vent - White part # 37202-29125 is designed to be a roof vent. I recommend to use 2-Piece Polypropylene Trailer Vent for 3" Diameter Hole - Black part # WHMAV2-WAVT2 which is designed to be installed on the side walls of your trailer and has a cover to prevent water from getting in. I have attached a very helpful video for your reference. You will need Zinc Sheet Metal Screw - 8 x 3/4" Indented Hex Washer Head part # 31071 to install it.
    view full answer...
    Image 1 for
  • Attaching the Redline 2-Piece Roof Vent to the Front Side of a Cargo Trailer
    Yes, you can mount the Redline 2-Piece Roof Vent, # 9139, on the front side of your cargo trailer. You will want to mount this vent with the vent slots facing down to prevent rain water or other elements from getting into the trailer. If you are looking for vents for the front side of your trailer, then I would recommend the 2-Piece Polypropylene Trailer Vent, # HMAV2-AVT2. This vent is designed specifically for the sides of trailers and is an inexpensive option that is also available...
    view full answer...
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  • Best Mounting Orientation of WAVT2-WHMAV2 2-Piece Polypropylene Trailer Vent
    If you mount the Redline 2-Piece Polypropylene Trailer Vent # WHMAV2-WAVT2 with the exterior part's flat slotted side facing forward (to increase air flow) there will definitely be a greater probability for rain and splashed water to enter the trailer. Still, as you noted from the customer-submitted photos we show on that item's page some have done this, and surely for the same reason. If you happened to stay in dry/desert areas this will be less of a concern but since you are in the...
    view full answer...
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  • Function Of Trailer Vents On Enclosed Trailer
    The vents we offer for an enclosed trailer like part # 9139 are designed to allow air into the trailer. None of the vents we offer create a pressurized condition in the trailer and none are equipped with an air filtration system to keep dust out. Some of the features on the vents like # 9139 allow you to adjust the amount of airflow in the trailer with a butterfly valve mounted on the inside of the vent which would be operated from inside the trailer. Other trailer vents, like part #...
    view full answer...
  • How Does Enclosed Trailer Vent Keep Rain Out of Trailer?
    The enclosed trailer vents we offer are designed to keep the rain out and the best option would be the 2-Piece Side Vent for Enclosed Trailers # 9139. As you can see from the accompanying photo the exterior piece is angled to keep rainwater out and it also has an interior baffle that will direct rainwater to drain holes in the corner of the vent. The butterfly vent also allows you to close it if you'd like. To install this vent you will need 20 screws and four #10/32 machine screws as well...
    view full answer...
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  • Trailer Roof Vent Recommendation for Moving A Lot of Air Even in Rain
    We have the Fan-Tastic Vent Roof Vent w/ 12V Fan # FV802250 which has a larger fan in it that can move 920 CFM. For a cover to help prevent rain getting in we have the part # FVU1500WH which will go over the top of the roof vent when open and allow the vent lid to be open with the fan moving air at all times. For a side vent we have the part # WHMAV2-WAVT2 but it does not have a filter built into it.
    view full answer...
  • Can a Solar Powered Plumbing Vent be Used on an Enclosed Car Hauler Trailer
    You could use plumbing vent # UF53-945001 for your enclosed car hauler trailer. On the inside what I would do is get some screen (like for windows) that does not restrict air flow (as good for air flow as you can find) and cover the opening on the inside of the trailer. But this fan has a very low cubic feet per minute air movement rating and might not be the best option. Another option is to use vent # HMAV2-AVT2 or # WHMAV2-WAVT2. The openings point down so installed on the side or front...
    view full answer...
  • Availability of Vertical Mounted Vent Fan
    The rain shield used by the MaxFan # MA00-07500K Deluxe Roof Vent Fan does an excellent job of excluding water when installed in its typical horizontal orientation, but simply stated the fan wasn't designed to be installed horizontally. The vent would admit water into the interior of the vehicle. In addition to that, the varied turbulence that would be experienced at the rear of the vehicle rather than straight line winds it would see mounted to the roof would likely tear the vent fan unit...
    view full answer...

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Info for this part was:

Employee Raymond P
Written by:
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Employee Jameson C
Expert Research:
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Employee Chris R
Video Edited:
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