a few problems

first problem is the fact that my windsheild wipers only work on high
2nd is that my back windshelid wiper dosent work it just makes alot of noise and wiper fluid comes out but it will work if u edge it along
3rd my power mirrors do not move any suggestions. And fourth my drivers side door speaker only works from time to time and the same with the drivers side back door while the passanger side back door speaker dosent ever work. Any suggestions on any of these problems?

Not sure what year blazer you have but there was a recall on the windshield wiper motor on I think it was 95-97 but to be sure you can go to:

http://www.alldata.com/recalls/index.html
for recalls on your vehicle and see if some of the problems you are having are covered under a recall. The power mirror switch on my 96 is a little screwy and from what I hear, many of them are. Your speaker problem could be a loose connection or it could be blown- have to take the door pad off either way.
Good Luck