I Have a 2002 Trailblazer. For the longest time the a/c has only worked on number 5. Many times it goes on and off by itself. Recently it has not been wanting to shut off even when the ignition is off. Eventually it final can be turned off. That has now changed. Yesterday on the drive home I couldn't get it to shut off. I eventually had to disconnect the battery. When I re-attached the battery this morning it still was on. It never turned off on the drive in. Please help.
Thanks

 

The clue here is the #5 works- and the rest dont.

You have a problem with the resistor module that controls the fan speeds.
#1 thru 4 have their own resistor and power source.
#5- gets its power from a different source than the other 4.

thats why #5 continued to work.

the good thing is that this is an easy part to fix.
cost is about $30. and is available at dealer- and some auto parts.
it is easily accesible from the area under the glove box.
a few tools and about 20 minutes and you can change it..
if it still blows with key off--- then something else is up---
but you will have 1-5 working back.

tools you need
7mm socket or nut driver
7/32" socket or nut driver
one long screw driver (flat blade) - optional
flash light - optional

at Autozone-- the replacement part is made by Duralast.

Part # DR755


AcDelco # is 15-81095