Lawrence-
Your fridge and charger should be okay, but there are a lot of things you should be aware of.
Whenever you stay at a relative's, etc., or plug in at home, determine 1) the condition of the outlet its proposed to plug into, 2) the size of it, 15 or 20 amp, 3) what else is on the circuit - preferrably not a freezer that's not on its own dedicated circuit in a garage for example, and 4) how long of an extension cord is involved and its condition. More roof air conditioners have been ruined by inadequate voltage than you can imagine. I may use one AC on a 20 amp source, but only with everything else turned pretty much off or to gas/diesel operation, and then only in the worst ambient weather situation. As a rule I don't use AC except with at least 30 amp or on the generator.
You can get by on a long cord at the end of a 15 amp circuit, but don't use your AC, and keep other things like electric hydronics (AquaHot, HydroHot, Hurricane, etc.) and space heaters minimal or not in use. Your fridge should be okay, but if something else like a microwave or your on-board charger or a hydronic's electric side kicks in at the same time the fridge or other device is cycling on, the circuit may not handle the voltage drop of the long cord and the load at its end. I dunno about your '99 and if it has the option, but on our '06 coach I try to remember to reset the Magnum inverter's control to match what I'm plugged into - 15, 20, 30, or 50 amps - to help protect the system.
A 20 amp circuit is better, and capable of an air conditioner, but it'll be at its limit. I still wouldn't use my AC on that except in rare conditions. When it starts up, an AC's motor draws a lot of juice - if it has to work too hard to get that juice due to limitations upstream, it can burn up. If anything else cycles on it puts the AC at risk, even if the house's circuit breaker or fuse holds up.
I've adapted down to a 14 gauge cord to my 30 amp RV house outlet before, when my daughter's trailer was on it at the same time, but even though the coach was essentially in storage, I went in one day and the satellite dish on the roof was cycling wildly. I ended up frying the 20 to 30amp adapter outside on the ground because the adapter was relatively cheap and poorly constructed. Weird, but at least the on-board system protected itself and all inside the rig was okay afterwards. There are different grades of cords and adapters. You get what you pay for in that regard. Stay as heavy duty, over-built in those depts. as you can.
I went to top-grade heavily built adapters instead of the common little black ones, and carry 50 ft. 12 gauge cord (yellow) on board to limit voltage drop when gunkholing off relatives' garage circuits. It's a good idea to keep adapted connections out of direct rain where possible, or at least elevated so not in contact with the ground, especially low spots where puddles can form - an adapter will short out literally to ground and melt down before a 30 amp circuit can blow - that happened to the little triangular black adapter, that was lying on a micro-lowspot on concrete during a Northwest gullywasher, and that my daughter was using for her trailer - I replaced it with a big yellow pigtail type and looped it over a peg and under a plastic cover on a nearby fence.
If you have an Aladdin, it's a great tool for monitoring your amperage use. When you know the limit of the circuit you're plugged into, the Aladdin will tell you how much total you use as you turn things on and off, so you can develop an idea of what you can safely get away with. You'll soon know how much amperage each device normally takes. When at a relative's on a long cord, 15 amp garage circuit, the fridge is okay, and we'll watch a little TV at night (we're night owls and most of them working stiffs). The HydroHot's electric side is switched off, and we may use the microwave sparingly (keep in mind the fridge cycles on and off, as might the inverter's battery charger if it's not in Float mode yet). In a pinch we might force the fridge to gas side only, but that's rare. In the morning I may use the coffemaker, but watch the Aladdin closely. As you may be able to tell, a 20 amp circuit means a little less caution in the appliance use dept.
-Joel
