Help: 2003 chevy silverado 6.6l heater problems.

[Ramhoes]

Hey my dad's got the truck and the heater for some reason it isn't blowing hard anymore. Still blows and defogs the windows but just not strong anymore. Anyone have had the same problem and able to help point out what to look for? Also hopefully this is in the right forum!

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[Burn Down]

Maybe a weak fan motor or the resistor is taking dump (very common failure, resistor). Hook a multi meter into the the fan motor power wire and read the voltage on high, should be system voltage 12ish or so.

 

[malibu795]

03 still has cabin filters iirc.... Bet they're are plugged full