08 Chevy Colorado ac/heater fan not working.

Charlie, 1st thing is to check your fuses. I will post some links to help you see and solve problem. May not be your exact model but steps are basically the same.
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Can you hear the front ac/heater fan? They use the same AC compressor so that should be okay. The fan switches fail quite often on those. That controls how much air is pushed by the fan for AC, heat and defrost. The switch is attached to the fan knob on the dash.

if the lower fan speeds dont work but the fastest speed does the heater fan resistor block needs replacing. If the highest fan speed doesnt work leave it on there and check for power at heater blower fan, if power is on one wire and the other is an earth the blower motor fan needs replacing. Use a normal globe test light to check this. If no power on any wires to fan go back and check all fuses in car and under bonnet with same test light. If fuses are ok possible open circuit wire to fan.

I had the same problem. It turned out to be the ignition switch. i have no idea how that is connected to the fan but... it worked, got me my fan speeds back, although it is not working again...

the blower motor has no affect on the AC system,
start the engine and turn on AC and watch the AC compressor to see if clutch engages,if it doesn't the system isn't full,if you are correct the clutch should be engaged and should quit when you change heater speeds,

try changing the compressor relay

Both my rear brake lights went out at the same time. o7 chevy colorado. What are my options?

Treed55508,

Try this solution. I have had the same issue three times. A Chevy tech told me that if it keeps doing it, to replace the blower motor, as it seems to be a chronic problem with the blower having to much resistance and thus burning out the resistors. I suspect that you probably had lost one speed first and then more. It has happened both ways with me, once the entire thing went out at once and then the other times it goes one speed at a time.

http://sparkysanswers.blogspot.com/2008/07/2005-chevrolet-silverado-blower-inop.html

your speed switch located in heater box usually one wire to it in passenger feet area above "TOES" usually you loose 1 or 2 speeds on fan but it is unplugged or completely cooked good luck!

either blower motor resistor or blower selector switch.could be selector switch because if resistor was gone you should still have either hi or low fan speeds.