1992 4x4 lights flashing intermittently
 

Ok so I've searched the forums and Google only to find out that my flashing 4hi and 4lo buttons (both flash then stop then flash again a few seconds later) is either the switch or a bad vacuum. Well I replaced to switch with a switch from another blazer of mine that I know works. Nothing. We traced the vacuums and looked for holes ect but found nothing. Actuator is good, also. When I press the 4hi or low, nothing happens, no noise no nothing. I've heard about the switch thing on the t-case being bad but it seems that when it's bad, there's no flashing lights associated with it. While the vehicle is running, however, I can hear a kind of sucking sound associated with a vacuum leak and it stop when you turn off the vehicle. Okay with that being said, my heat is stuck on haha. I replaced that bitch of a switch, too. No matter what position you have the temp, position selector or fan speed, it's always on heat and floor. I don't think it's stuck on the lowest fan speed, I think it's just blowing out because of the driving because you can't feel the heat when stopped. Maybe a fan or relay? Are both problems tied into a vacuum issue? If so, whereabouts is my issue? Behind the dash? Under the hood? I'm normally pretty good with these issues but I'm lost. Taking a multimeter to everything in the am. Thanks in advance!