well i have 2 issues with my heater,first one being that it will only blow when i have it set on four and i don't know what i have to change to fix that.secondly,sometimes when i acctually get it to blow it won't shut off. i have figured out that if i pop the hood and jiggle what looks to me to be a switch or relay of sorts onthe fire wall it will shut off.i just need to know what exactly that part is so i can order one and change it.any helpful info would be greatly appeciated!!!

 

Speaking of helpful info... what year and model is the vehicle, and do you have manual HVAC or automatic temperature control?

 

sorry i forgot the most important info.it's a 1998 s-10 blazer 4x4 and it has manual controls

 

More than likely the blower motor resistor is faulty causing speeds 1 through 3 not to work: Buy ACDelco Blower Motor Resistor 15-71991 at Advance Auto Parts____ The resistor is located in the evaporator housing, (accessible from under the hood) and requires cutting of the soft plastic housing to replace it. There is a line scribed on the housing with the words "cut here for service".

The high speed blower relay is mounted to the firewall and might be what's causing the blower to remain on. The orange wire at the relay has battery voltage at all times so once the relay is latched, if the contacts stick, the blower will remain on even when the ignition is turned off. Might be worthwhile replacing the relay.