I have a cover for the TaB side of the 7 pin, but unless you keep it upright, it collects water. We used zip ties and a fist clamp. This is actually the end of our brake controller.
I know there are protective devices out there for this purpose (protecting against water entry into wires & connectors) but have never experienced any issues/problems with any trailers owned over the years (via the wiring), nor water migration into the wiring itself.
I will add however that in the utility industry there is an issue with water wicking (entering cables) into exposed aluminum cable ends that are left exposed and open to the elements (e.g., via rainfall, laying in ground water, etc.) and that water that does enter into an aluminum conductor creates a chemical reaction that can break down aluminum, cause aluminum to oxidize, turn it to a powder, the cable and jacket eventually swell up and will eventually causes a cable failure. To eliminate this from happening cable ends are capped off with a heat shrink cap after the cable is cut and the ends are protected from any moisture entering the cable ends.
Copper conductors are more forgiving but will react with aluminum conductors (when spliced together) and this requires care and using connectors that are designed for the application undertaken. I believe that any means of protecting a 7-pin cable connector from water entry whether the end is protected with a cap, covering it up with plastic or merely hanging the end downward to protect it from the elements and water are all good and preventive means of keeping it in operable/safe condition.
Mike - Elmira, Mi / 2019 T@B 400 / 2021 Chevy Silverado LTZ
I take back my previous self assurance. After incredible deluges this weekend the rain got into the plastic bag anyway. I thought of @ChanW remark, and going to try it next time. Sigh...
2017 T@B 320 Max S silver and cherry red, L@dybug ("Bug" aka my esc@pe pod), TV 2015 Toyota Highlander aka Big Red
@Luckyj, Absolutely agree. Both ends, including the connector for the tow vehicle. reduces corrosion as well, so it's a win-win. I use it on my shore power plug as well, including a little on the threads of the connector. Makes it much easier to screw the connector on. Dielectric grease is absolutely your friend on all electrical connectors. I just put some on a Q-TIP to apply it. Keep a little plastic container of it in my tool section of the trailer.
2016 T@B MAX S-aka: WolfT@B TV: 2006 Chevy Avalanche LT Z71 aka: WhiteWolf, or 1972 Chevy Custom10 P/U aka: SnarlingWolf Spokane, Wa. Eric aka: Lone Wolf