Actually, the female plug on the car. Standard 4 wire flat plug seems to always get the brunt of the Minnesota winters and road salt. This is on a 4 Runner. The original lasted 6 years in Florida, before I bought the car. I go through a new car side plug every year. Have tried super cleaning and protecting it in multi layers of tape, using plastic bags, etc., etc. - but whatever is corroding the sockets still gets in there. Also have to replace several feet of wire, as it always has "black wire" where all the copper corrodes inside the insulation.

Should I buy female plugs by the case, or does anyone have advice on how to prep things so I don't have to do this again next spring? It's a pain to sit outside the storage yard and rewire the plug so I can get the boat home. (Yes, I always say: "It doesn't look too bad, this year it will work!")

If you're going to keep that vehicle, why not take the time, and revise the wiring so the plug stays inside the truck, rather than dangling outside? Get under there, look for a grommet or hole plug that you can use, and solder/shrink wrap a new 4-flat on that gets protected.
HRG

I deal with the same problem during Utah winters with all the road salt. You need liberally coat the contacts/crimps with grease. I literally fill my socket. Dielectric grease available at autoparts stores works best, but regualr axle grease or plain old vaseline works well too.

After you pack the female plug with grease, buy a male plug, cut the leads off and plug it into the female plug. That will help prevent water/salt intrusion. I did this with a Chevy van that had exposed trailer wiring and it seemed to prevent plug corrosion over the winter.

I just drench mine with WD40,then a few wraps with electrical tape. But I don't even bother to tape it every year, because I occasionally use it in the winter when I tow a snowmobile trailer. It still has the the original plug I put on 10 years ago. It has been through that many Chicago area winters which are about as corrosive as any with as much salt as they use around here. At worst I occasionally have to scrape a little green corrosion out with a small round file,but never had to change it. Just hooked up the boat last week for the 1st time this year,still no problem.

I'll try the grease and male plug trick next fall. Minneapolis seems to be worse than Chicago for salt, I guess. I've tried the super seal with tape routine (a whole roll!), no go. And with this particular vehicle, looping it back up into the cargo area isn't ideal. Just something else to think about when I get to the point of trading in the vehicle!

Thanks for the suggestions!

I've done the dielectric grease/male plug thing for 3 seasons thus far and she's still good as new.

WD40 does work but its thin and washes out very quickly, a light spray of Lloyd's AD200 couple of times a season works great for me, its dielectric, doesn't harm rubber or plastic and doen't attract dirt, I use it on my trailer leaf springs(stops those annoying squeeks), light bulb sockets, winch, jack and the plugs, 5 years in Canadian winter and no sign of corrosion.
http://secure.idiind.com/TriggerWorkflow.aspx?WorkflowModuleGUID=dc50596f-10a2-487c-bbc3-e331d55ef3ab&ES_ProjectGuid=e9b12a0f-806b-455a-8293-79bbdd4f9beb&CountryCode=&LanguageCode=&CC_CustomerGuid=&PC_ItemPropertySetGuid=42e22a59-7218-428b-a9ad-017a948ccd85&PC_ItemPriceCodeGuid=&Action=Item+Details+Page&ReuseToken=True&TokenGuid=5cbcc92d-d0b1-4dee-8bd4-e4013494367d

Actually WD40 does not wash out. It dries but It leaves a water resistant protective coating that repels moisture. Over the winter I might treat it a second time if I think about it,and like I say do not even always tape it. The WD actually stands for "water displacement". It has always worked as advertised. Not familiar with Lloyds. Though the WD40 works well,I will check it out if can find it.

In years past on other vehicles I actually tried using a squirt of fogging oil,figuring probably would have good film strength. But it actually washed out pretty easily and did not work well. The WD 40 worked better.

I take care of a fleet of landscape-plow trucks. With all the salters we have on the back of the trucks, corrosion has been a major problem with our trailer plugs. I started using this product with good success-

http://www.noco-usa.com/pdf/Noco-Catalog-Chemicals.pdf


I get the small brush-on can and use it on the inside of all my 7 wire trailer plugs. This stuff sticks to anything and doesn't wash off. It isn't cheap but works good. Now that I have the corrosion problem solved, I just have to find a way to keep the guys from backing into a snowbank and breaking the trailer receptacles.

I agree with Hot Runr Guy. Rewire so the plug stays inside the truck. I've had my last two vans wired so the plug stays inside the truck. My local trailer shop suggested this to me years ago when I had similar problems. I have not had an issue with the harness wired inside the truck these past 20 years.

Like2Fish