Rick, electricity isn't all that complicated. Yes, it can be dangerous IF you touch things you shouldn't, but most testing can be easily and safely done.
The first step is to follow the electrical path. Do you have electricity at the plug, the point at which you are plugging your coach in? That might be an outlet on the side of your garage or a campground's electric pedestal. Your meter will tell you that. No power there means no power in the coach.
Assuming that you have power coming into your coach, your next step is to figure out where you do and don't have electricity. Again, a meter is helpful, but you can accomplish the same thing with any small item that can be plugged into a standard outlet and will work only when plugged in. Check every outlet and note which ones work and which ones don't. Don't forget to check the refrigerator. If you have a residential unit, it only works on 120 volts. Make sure that your inverter and generator are OFF, then open the door. If the light comes on you have power there. If it doesn't you don't. Look for 120 volt lights, too. You may have one in the dining area, and another one over the range. Do they work? Be sure to look in the basement, too. You may have a separate converter that turns the 120 volts into 12 volts. Don't confuse that with the inverter, which turns 12 volts into 120 volts. Check the air conditioners, too. Just turning on the fan is enough.
Once you know which things work and which don't you can focus on the non-working things. What do they have in common, besides not working? Are they all on the same circuit? If so, you may have a tripped circuit breaker. Reset the breaker for that circuit and check again. You may have more than one circuit that has tripped, so be sure to check for that. This is a good time to update your manual to list everything that is on each breaker.
You may have more than one GFI outlet, so just because the one in the bathroom is on doesn't mean that there isn't another one in the basement somewhere that has tripped. You can buy a small tester that will let you know exactly which outlets are protected by the GFI. This is the one I have: Bastex Socket Tester with GFCI check. Receptacle Tester for Standard AC...
You can get them at Wal-mart, too, or even some grocery stores. Point is, they are cheap and readily available, so you should have one in your coach all the time and another one at home. To test the GFI you just plug the tester into an outlet and push the button on the top. If it trips the GFI you know that the outlet is protected by the GFI. If it doesn't, it means that either the outlet is wired into the circuit before the GFI or it is on another circuit. BTW, this is an ideal test device to carry around and plug into outlet to see if they have power or not, since the lights will light up if power is present.
Okay, now you know how to test, so let's move on to what to do about an outlet that doesn't work.
If resetting the breaker in the panel doesn't work, and the outlet isn't protected by a GFI, you may have a bad outlet or a broken/disconnected wire. Turn off the breaker for the outlet in question and verify with your meter or tester that the outlet is dead. Take off the cover plate and look inside the box. A flashlight may be a help here. Do you see a wire that looks like it isn't attached to anything? You may have found the problem. If not, remove the outlet from the box and check the connections. There should be enough wire to pull the outlet away from the box a few inches, but not more than that, so don't get carried away. Do all of the wires appear to be firmly attached? If so, put the outlet back the way it was and go on to another outlet. Remember that wire costs money, so the outlets will be wired one after another, starting at the breaker box and ending with the one farthest away from the breaker box.
Unfortunately, you won't be able to see much more of the wires than the little bit in the outlet box. For some reason, mice seem to like the taste of the sheathing on electrical wires, and dealing with their damage is beyond what I'm going to talk about tonight.
Back to your original question, how long have you had this coach? Have the outlets ever worked? If yes, when did they stop working? What happened then? Sometimes answering those questions will lead you to the problem faster than starting at the outside connection.
Oh yes. Do the outlets work when you are disconnected from shore power but running on the generator? If that is the case, your transfer switch may be the culprit.
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