I had to have the four-wheel drive system serviced/repaired about three times, and it still did not function correctly. Push-button 4x4 systems are destined to die when you need them most. Sometimes it engaged, other times it did not.
I went through two alternators. The stock alternator died at around 125,000 miles, and the replacement died less than one week after I had it installed. It's not fun driving on the highway when the bolt shears off the alternator and proceeds to slice the serpentine belt in half which then gets tangled around the fan.
I went through two serpentine belts. One because it was old and needed to be replaced, and the second because of the alternator incident.
When I first acquired the vehicle, the A/C blew warm. I brought the vehicle in for service and the A/C was recharged and blew ice-cold.
This vehicle has to have one of the worst braking systems on any vehicle I have ever driven. Even after replacing all brake pads and servicing the rotors and drums, the brakes would either work correctly or the ABS system would kick-in for no apparent reason which has sent me through a number of stop signs.
Perhaps the biggest problem I had with this vehicle was the rust. No matter what I did, the rust spread like cancer and eventually ate through the bottom of the driver's door and through driver's side fender, which caused the fender trim to come off when I was washing the vehicle.
Driving the S-10 Blazer is like sex, when it's good it's great, but when it's bad, it's still pretty good. For all the grief it has given me, the S-10 Blazer was also there when I needed it. Even though the 4x4 system was not functioning properly, during one of Pennsylvania's harsh winters, I was able to pull a disabled Dodge Ram 4x4 that sunk into the ground with my 13 year old Blazer.
The doors and fenders on an s-10 or s-10 blazer are notorious for rust. If you drive in areas where salt is used, it is GOING to rust. I have had six blazers ranging from 87-94 and three s-10's, 89,91,93. They all rust. One thing is for certain, they are probably about the best vehicle GM has ever built. I have had less problems with these vehicles than any other GM product I have ever owned. I bought my 87 used in 94 with only 55,000 miles on it. I drove it till it had 202,000 miles on it and it still started right up every time. I had to put a belt, alternator, and battery in it and that was it, other than normal wear items like brakes and fluids. Sometimes they can be a headache, but for the most part, they are awesome trucks.
Every early 90s Bazer I've seen has rust. Theres a guy in the building next to my job who has an early 90s Blazer: its white paint doesn't do a good job hiding all the bondo around the front fenders and there's rust all around it, both side rocker panels have rusted off, and there's some rust in the rear as well, but it does run very good.