Im new here so hi to everyone. I bought a 97 Blazer and i have a couple of problems. 1 is that the 4wd doesnt ingage lights come on but nothing in the front turns i assume by all the other post it probably a vaccum or actuator correct? 2 is that when i turn the ignition on sometimes the instrument lights come on and sometimes they dont. When they dont it will not start at all(but it does turn over) and when they do come on it will start right up and the wipers work when they want to, gonna go ahead and say thank you for all the help,

 

1) Yes it sounds like a vacuum issue but if you could engage 4 wheel drive and have someone look under the truck (from a safe distance of course) to see if your driveshaft is turning then you would know it's an issue with either you vacuum system or a broken cable from your actuator to front differential.
2) I would suspect that you might have some burned contacts in the RUN portion of you ignition switch but that would be just my first stab. If you have a wiring diagram it would help you a bunch. When this happens have you tried to wiggle the key. The switchitself is located down the column on the top.
3) Your wiper switch (multi-function switch) probably is quite worn but you need to check with a meter to see if you get good contact.