FYI: You can purchase a 7-to-4 pin adapter at auto
and RV supply stores. If you have a 7-pin female electrical
plug on your car, this will convert it to the American
4-pin plug on many trailers.

I use two tow vehicles -- a Toyota pickup for some weekends and an RV
for others. The pickup has both 7-way blade and 4-way flat. The RV has
6-way round (that's with one in the center). A problem I had (until
yesterday) was I could not find a 6-way to 7-way adapter, only 7-way
to 6-way (which of course are backwards gendered), so when pulling
with the RV I had to use a 6-to-4 and a 4-to-7, which looked like
something Rube Goldberg put together. As my engineer reported in my
earlier post, there was a problem with the 4-to-7 adapter. He fixed
that, and did the rewiring that Marc suggested, now everything works
-- with his van at least.

2NO