Repairing and Restringing a Broken Midi-Heki Vent

The Dometic Midi-Heki Vent has a mixed following in the RV community. Some have a love-hate relationship with the imported vent, while others simply love it or hate it entirely. One unhappy owner in a forum rightly called the expensive and complex vent, “nicely conceived, but very poorly executed.” Unfortunately, he’s right. Most who have this vent love the terrific views and fresh air that the vent provides, yet hate how it overheats and is prone to breaking. Being a European import, it’s also a very expensive vent to buy repair parts for. The biggest problem with the vent is that its made out of plastic and acrylic. Neither is very durable. The acrylic dome is prone to cracking from large hailstones, while the plastic components found inside the vent are prone to breakage from UV rays and heat after years of use. The sun and heat are particularly troublesome for those who live in warm and sunny climates like those found in Texas, Arizona, and Florida.

One particularly troublesome issue relates to the sliding bug screen-privacy shade. The entire mechanism consists of a complex arrangement of spring-tensioned strings that are kept in place by retainer tabs found on the top of each slider bar. The problem with these retainer tabs is that they can be weakened over time from UV exposure and heat and can break, unraveling the strings and leaving the owner with one, big tangled mess. Unfortunately, replacing the bug screen and privacy shade assembly will set you back an eye-popping $368 if you order a replacement from Dometic. This works if you have the funds to do so, but a better and cheaper way to address the problem is to use a tiny wood screw instead. Yep, you heard me right—a tiny wood screw.

Closeup of intact Midi-Heki Vent plastic retainer tabs on top of one of the sliders.

Making the Repair

Overall, the repair is quite simple. Before you start, however, you’ll need to remove the entire lower assembly of the Midi-Heki Vent from the vent opening. To do this, remove the four retainer screws—two screws on either side, which can be found underneath the ventilation grid covers. Once the assembly is removed, place it on a large flat table or workbench with a large towel or blanket to protect the assembly from scuffs. Next, drill a tiny hole and insert the wood screw where the broken tab used to be. Use a wood screw only as the top is flat and won’t catch on any of the vent’s internal parts. You’ll also want to make sure the screw is inserted far enough so that the top doesn’t protrude and catch on anything as the slider bar is slid back and forth. The idea with the repair is to create a way to keep the string taut and in place as the slider bar is moved. The photo below illustrates where to insert the screw.

Closeup of a wood screw used to replace a broken retainer tab.

Hopefully, the affected string in your vent didn’t become completely unraveled after the tab broke. Consider yourself lucky, if it didn’t. If it did, then you might have a bit of a challenge putting it back. Unfortunately, Dometic doesn’t offer detailed instructions on how to restring a Heki, only a basic diagram, but Rory Willet, the owner of BundutecUSA, explains how the strings are connected and work better than anyone else we know. “There is an anchor end and a spring-tensioned end,” he said. “There’s a spring in each corner that’s in the opposite corner of the anchor. The string runs into the plastic slider bar, across to the other side, down the side of the trim ring and anchors to the corner. There’s a spring in each corner. One end, the springs stick straight out the end the other side the springs are 90 degrees, coming out the side. So they zig-zag, keeping everything relatively square.” The official Dometic replacement parts diagram below helps illustrate Rory’s description.

The official Dometic parts list for the Midi-Heki provides a useful diagram on how to restring the vent.
Closeup of one spring-loaded anchor points on a Dometic Midi-Heki Vent.

Hopefully this fix addresses your problem with the vent. If not, then you’ll probably need to order a replacement part. If you need to go this route, we recommend going through the manufacturer of your RV rather than going through Dometic. It’s cheaper and easier that way. Not only that, but you’re better off ordering a whole vent rather than ordering a large part. For example, a replacement dome from Dometic costs $652, while the complete bug screen-privacy shade assembly with the alignment strings costs $368. You can get the entire Heki Vent from your manufacturer for about $700. Sure, this approach is expensive, but you’ll have every replacement part you’ll probably ever need for a lower price than what you can get from Dometic. However, if a small replacement part is all you need, then going through Dometic might be the best way to go. To order a part, you’ll need to know the model number of your Heki Vent and the part number before you call them. For your convenience, we’ve provided Dometic’s official parts list here. For additional information and tips on using the Dometic Midi-Heki Vent, check out our recent review.

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About Mello Mike 446 Articles
Mello Mike is an Arizona native, author, and the founder of Truck Camper Adventure. He's been RV'ing since 2002, is a Jeep and truck camper enthusiast, and has restored several Airstream travel trailers. He currently drives a 2013 Ram 3500 4x4 pickup truck with a 2016 Northstar Laredo solar powered truck camper mounted on top. He enjoys football, music, hiking, travel, photography, and fishing. He retired from the U.S. Navy in 2004 as a CWO3 after 24 years, worked in project management until 2017, and now runs this website full-time. He also does some consulting and RV inspections on the side.

4 Comments

  1. Thanks Mike for the very informative article, the pictures are a great addition. Personally, after all I have read about this product I can’t image how it is still in production. I have long ago concluded that any RV of mine will not have one of these units. However, I do have a question. Many manufacturers speak about the ability of these vents to provide emergency access that may or may not be code. What would those of us do in the event the builder will not provide a pop out bedroom window because they insist on using this product to satisfy any possible codes? My travel trailer was built with a fixed pane pop out style window in the bedroom to provide emergency access. Personally, if no choice was given the purchase would not be made. I wonder how many builders consider this an issue.

    • They are a pain, and great at the same time. They are also mind-numbingly expesnive.

      They do require extra attention. Leaving them closed in full, hot, sun can warp the plastic, the string can break, if you don’t close them fully (turning the handle three more times than you’d think) they can come open and rip off when driving. They scratch, like all plastic windows, very easily. The bug screen doesn’t reach all the way to the edges.

      BUT …. if you know what the issues are and deal with them, they are ok. Lots of air, great for night sky viewing. If there was another option I would take that but I don’t think there are many.

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