Usually turns out to be the resistor, but can be the switch, test it this way:
BLOWER MOTOR OPERATES AT HIGH SPEED ONLY 1. Turn ignition on. Set blower switch to speed that does not operate. Connect test light between wire of inoperative speed position at blower switch and ground. Low speed is Yellow wire; medium speed is Light Blue wire. 2. If test light does not glow, replace blower switch. If test light glows, connect test light between Yellow wire or Light Blue wire (depending on switch position) at blower resistor and ground. 3. If test light does not glow, repair open Yellow wire or Light Blue wire between blower resistor and blower switch. Go to next step if test light glows. 4. Connect test light between Orange wire at blower resistor and ground. If test light glows, circuit is okay. If test light does not glow, replace blower resistor. Page 1 of 1 HEATER SYSTEM -1994 Chevrolet Astro 3/30/2009 There are two relays, one in the cab fuse block the other for high blower on the relay brackett on right rear of engine compartment. The reisitor is on the blower case.
Monday, March 30th, 2009 AT 2:59 PM