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ray_mcavoy · 02-21-2015, 05:05 PM

The switch should be receiving full battery voltage on the brown wire. It sounds like you have a bad connection somewhere.

Starting at the ignition switch, a 12ga brown wire runs from the ACC terminal to a bus bar in the fuse box that powers 3 or 4 fuses. One of them being the HEAT / AIR COND fuse. From there, a 14ga brown wire runs to the blower fan switch. I believe trucks with AC have an added inline connector in this wire shortly before it reaches the switch.

I'd recommend that you start by checking the HEAT / AIR COND fuse to make sure it is making good contact with the clips in the fusebox. And check the fuse clips for any signs of rust/corrosion. Also check the voltage there at the fuse to make sure it is receiving full power from the ignition switch.

02-21-2015, 05:05 PM	#2
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,373	Re: blower circuit help. The switch should be receiving full battery voltage on the brown wire. It sounds like you have a bad connection somewhere. Starting at the ignition switch, a 12ga brown wire runs from the ACC terminal to a bus bar in the fuse box that powers 3 or 4 fuses. One of them being the HEAT / AIR COND fuse. From there, a 14ga brown wire runs to the blower fan switch. I believe trucks with AC have an added inline connector in this wire shortly before it reaches the switch. I'd recommend that you start by checking the HEAT / AIR COND fuse to make sure it is making good contact with the clips in the fusebox. And check the fuse clips for any signs of rust/corrosion. Also check the voltage there at the fuse to make sure it is receiving full power from the ignition switch.