We could all probably list many stories about wiring in Mexico. They use 15amp outlets but have 30amp breakers. We do not know if they use the proper wire - 10awg for 30amp - 12awg for 20amp - 14awg for 15amp (yes, I now it is probably not all awg). Black or red wire can be common and white wire could be hot - all wrong. There is often no ground. Lots of workers in Mexico (and the US) think they know how to wire an outlet - but many do not - there may not be real electricians around who really understand this stuff. Never count on properly wired anything - anywhere.
Maybe 6 years ago we were in Chetumal and the fancy RV park there was upgrading. They put in a lot of new electric stuff. We parked and I plugged my meter in only to find wrong polarity. I checked other sites and found several problems. I rewired our site outlet. I talked to the manager and showed him some of the problems. He did not know what to do or who to have do it. I spent some time and did some Googling and wrote up a bunch of info for him showing wiring and plugs and outlets etc. I have no idea if he fixed it or had it fixed but at the time he did seem to be very concerned about it - we have not had reason to return so do not know if it is corrected.
Over the years we find many problems with electric wiring - mostly in Mexico but sometimes in the US as well - which is why we have our handy dandy quick plug in tester device. A while back there was mention on this forum by someone about how they wired up a reverse polarity outlet adapter - so I made one of those up to quickly plug in when polarity is wrong so I have correct polarity coming out instead of reverse. Some on this forum also carry grounding rods to pound into the ground if there is no ground at the outlet - so I have an adapter wired up to do that also. Not everyone can do these things.
But to be clear - I have some electrical background - knowledge - skills - and fully understand that not everyone is equipped with the knowledge or expertise to do any of this - or even be able to use a voltmeter or multimeter to test for all the things we might need to look for - it is not just a matter of checking voltage.
Anyone who travels in Mexico or plans to travel in Mexico should try to get some sort of device for testing both voltage and polarity - a plug in quick and easy - no technical skills required. The basic three prong polarity tester is what state electrical inspectors use when they go through a building to check wiring - no reason for more skill than plugging it in and looking at the lights. A plug in voltmeter will immediately tell you what voltage is coming out of an outlet. After we test outlets we plug the meter into our RV where it can be seen so we can glance to see fluctuations - say if we see lights go dim.
At an RV park in Matehuala I went around with my meter trying to find a good outlet - as I recall I found 2 I checked that showed up good on my meter out of about 10. Don't count on proper outlets even if they have been there for many years - with many RVers having plugged into them many times.
