I get that the dealer sees a lot of lookee-loos, but the purpose of a deposit is to solidify a deal, NOT to start discussions. Leaving a deposit before a price is agreed upon and a contract is written is foolish, and then the dealer will bend you over...hard.
Completely understandable that the dealer doesn't want to fire up all the systems if you are not serious about buying. BUT he should agree that everything works and if it doesn't he will fix it as part of the sale.
I agree I wouldn't waste time with the dealer, BUT if you want to go ahead here's what I would do, and that's inspect the trailer yourself.
First thing turn the fridge on. Note that it turns on, shut the door. If it runs for an hour or so you can tell if it is starting to get cold. If so it's more than likely OK. So while the fridge is cooling, take a look at the date codes on the tires, bring a voltmeter to check converter output, fire up the heater, unroll the awning, inspect the outside, check in all the closets, etc. Turn on the a/c as well. Crawl around underneath and look for damage.
I wouldn't worry about having water in it, the most expensive thing in the water system is the pump and that's $75, unless the tanks leak, and that is extremely unlikely.
Take a trip to the restroom whether you have to go or not, fake a phone call if you have to, then get back to that fridge and be sure it is getting cold.
Once you are satisfied that everything is working, then you can agree on a price, commit to an as-is contract and leave the $1000 deposit. If there are any "Oh we'll fix that's" during your inspection be sure they are itemized on the contract.
If you're not comfortable doing the inspection yourself, then give up on this dealer, because there's no way you will get satisfaction from him based on how he is dealing with you.
