If your label is intact it will state R-12 or R134. I have a 94 S-10 with an R-12 system. As Dmorse87 says they started fazing R12 out in some 94 & later models. You would need to convert to R12 & you can still use the original R12 compressor. But you need to convert the valves, evacuate the system, flush it, leak test, vacuum down etc. Mine still works, so when it stops working I'll convert..maybe!!

 

I converted to 134A my 1992 blazer had r12

 

late 94 to early 95

 

I converted my 92 S-10 Blazer to R134 when the compressor that came on it came to pieces on the inside. Flushed the system out right good to get the little bitty pieces of the compressor that were in the line along with the old oil out.

It cools just as good as the R12 did. That's been several thousand miles ago.

 

1994 Chevrolet S10 Blazer Tahoe LT 4-door 4x4 walkaround - YouTube

This is the 1994 Blazer I found and made a video of that had R-12, or at least used to have R-12. It was converted to R134a as evidenced by the red and blue valve caps on the system. Unfortunately it is NOT my Blazer. It was a recent trade (for a new Camaro) sitting on the back lot of a Chevy dealer near me (where my dad actually bought his S10 Blazer new in 1993), and the dealership owner's son let me have the keys and make a video of it for my collection of YouTube videos.

 

My opinion of R134a versus R-12 is that R134a works great when the vehicle is moving and there is air flowing over the condenser. However, when the vehicle is parked or sitting in traffic, that is when the cooling ability of R134a starts to suffer unless there is a fan blowing over the condenser. R-12 cools much more efficiently and can keep a vehicle cool even if it is sitting idle in 90+ degree heat. When the vehicle is actually moving, I have actually noticed that R-12 does blow slightly colder in some cases, but for the most part there is no difference when the vehicle is moving. My dad once rented a 1993 GMC Sierra 3500 Uhaul box truck to haul some furniture like 6 years ago, and the air-conditioner in that ratty old thing outperformed the A/C in my 1996 Pathfinder because it had R-12. I didn't know one Freon from another back then, but I am educated now and know why the A/C in the uhaul worked so good. The same thing with the 1989 Corvette convertible my uncle used to own. Unconverted factory R-12 A/C blew ridiculously cold even when car was not moving.

 

My dad's 1993 Blazer looked just like the one in the link you posted, except it was stock without the grille guard and stuff.