Check the plug that the blower motor plugs in to, also check the wires that plug into the resistor. You want to look for melted wires. Check the fuse box, look for the blower motor fuse. It will be really hot, so be careful. Pull out the fuse and see if the plastic is melted. If it is the fuse is loose and causing a bad connection.
04 379 heater issue
Discussion in 'Trucks [ Eighteen Wheelers ]' started by RisingBTrucking, Jan 26, 2026.
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Okay so I replaced the plug on the truck side that the blower motor plugs into. It was burnt out. New wires there. It worked good til I started driving again now the only way it’ll blow hot is on high but on high it pushes like it’s on the low setting.
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You did replace the resistor correct? Check for other burnt wires. See if you can get the fan switch to work by turning it between the settings. If you can it is the fan switch, and you can replace just the switch on the climate control panel.
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I replaced the resistor. On my panel I have to put it on the defrost setting for the heat ti come on. If you put it on any other setting it shuts the heat off.
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That sounds like the actuator. I must have miss understood, I thought the fan wasn't working properly
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