Fan Switch on my 2007 GMC sierra works on 1,2,&3 not 4&5 is the switch bad

SOURCE: 1997 GMC Sierra Ignition Switch Replacement

take off the cover on the top and bottom of the steering column just behind the wheel. pop the tilt lever out simply just by grabbing it and give it a good tug. then once you have the new switch and you get in there your going to need an inverted torx socket to remove the small bolts that hold the switch to the column. do not move the gear on the new switch make sure it lines up exactly as the old one did!!!!!!!!!!!!

SOURCE: replace neutral safety switch on a 1988 gmc sierra

Typically the Neutral Safety Switches are located with the gear selector, either in the column or the floor.

Hope this helps,
Tom

SOURCE: need wiring diagram for fan speed switch on 2003 gmc sierra

the fan control balast (or speed controler) is burned out. by design if it only goes high, its junk. replace it and youll have it fixed. should be by the fan under the dash on the passenger side.

SOURCE: 2005 gmc sierra fan won't blow high heat or A/C

check pins at the blower motor resistor
a- tan- med 1
b- yellow- low
c- pink - med 3
d- light blue- med 2
e- black- ground
f- orange- high
g- red- battery +
it could be the resistor

SOURCE: LOW OIL PRESSURE ON 2007 GMC SIERRA 1500. CHANGED

have it tested using a manual gage if still low then main baring ore most likely bad that would mean a over hall if is really low and bearings bad should be making rattle noise when started up first few seconds

Testimonial: "thanks alot.truck is not making a rattling noise.we did check it with a manual gauge.it read about 10 at idol. press. gets better as you incr speed"