1994
It depends on what year S10 you have.
Chevy switched from R12 to R134a for the model year 1994. Your truck should be R134a.
Need to know what year the Blazer is.
It switched with the 1994 model year.
depending on the year
Need to know what year Blazer.
We need to know what year that S10 Blazer is.
R134a, just like any other vehicle for that model year.
You didn't mention what year S10 Blazer you have but, the blower motor speed resistor can be found under the hood, on the passenger side of the firewall, close to the blower motor.
2005
2005
There is no headlight relays for this year, I have the same vehicle and I was pissed to find out its hard wired directly through the headlight switch itself.