blower motor runs with engine off
 

2004 trailblazer, has the auto climate system, fan will still run with engine off, doesnt have a resitor but a similar looking part with a heat sink on it, i beilieve its a control module of some sort, has a socket for a square 3 pin (i believe from the fan speed switch) and a pigtail coming out with 2 wires going to the blower motor. tried 2 different auto parts stores, they have a part that would pyhsically fit but it has a visable resistor on it and a flat-style plug in from the fan switch with more connection, looked like 5 or 7, didnt actually count them. i think this part i need is unique to the auto climate control, has a rocker switch for a fan switch rather than a rotary dial. either this part is called something differnt or its a "dealer-only' item. auto zone sems to think its a dealer-only part. what exactly is this thing called? and about how much is it? its held in place with (2) 7/32 screws, in the same place a heater control resistor would be, under the right side dash. its a co-workers vehicle, i dont have any pictures to post of the part,but hopefully ive described it enough. ON EDIT: read somewhere else on the 'net about a "speed control module" for the blower motor, is this the same thing im thinking i need or a seperate different part? since this aint my vehicle, id hate to get the wrong thing for it. my gut says its the control module ive described above, think the part # i need is 89018778. g.m. always has to make things over complicated.

well, update on this, it was indeed the control module for the fan speed. but the newer modules dont always play well with the older blower motors. even though the original blower motor bench-tested fine, ended up putting a new blower motor on as well. has been working fine since then. between this trailblazer & the one my sister used to have, i dont think id ever want one for myself. i have found a very good site that is specific to the trailblazer/envoy chassis: gmtnation.com