I recently got this 2004 Tahoe that is in great condition. The one thing that bothers me to no end is it is barely moving air. I hear the fan speed up as i increase the fan speed. When i change from window vent to passenger facing or floor vents it works as expected. My first thought was the cabin air filter... this Tahoe does not have one. On my 99 suburban, I could remove the blower and cabin filter and see the evaporator to insure it is clean but cannot see it with the 2004. I did poke my phone in there and all i can see looks clean, but i could not see the evaporator. I am actually thinking of doing the mod to add a cabin filter just so i can get a good look in there. Is there something else that can cause my issue? Why doesn't this rig have a cabin filter >.<

 

They were not standard equipment in 2004, but it sounds like you know about adding one to your Chevy. You may have an issue with an actuator not working properly if it does throw heat to one of the vents.

BTW, even newer semi-trucks are using cabin air filters these days. They are becoming standard equipment in many vehicles these days.

 

If it moves air OK in some positions then the evap is not plugged. All air goes through the evap. . Actuator or flap issue.
My '11 LTZ did not come from factory with a filter. I had to put a retrofit kit in it. Rock Auto had them cheap.

 

it is the same in every position through the window vent it moves air but it very much reminds me of my'72 K5 in that the heat leaks out reguardless of the speed of the fan and is the same as I move it to other vents.

 

I'd check the electric actuators under the dash. I replaced one on our 2005 Yukon, and on 1994 Suburban; air flow was going to wrong spot !!!

 

Verify the blower motor is wired correctly - it could be spinning in the wrong direction and that can cause the issue you describe. I’ve replaced a few blowers that had the motor leads reversed in the connector right out of the box.

Also many GM vehicles of this era often require blower motor and resistor replacement, and due to changes in the OEM designs, splicing in a new harness for the resistor or replacing the connector is required - if the harness has been repaired recently, the leads could’ve been reversed then.

I think the correct rotation is counter clockwise, so with the motor out but still connected, turn the speed on low and observe the rotation. Some wheels have the correct rotation or arrows indicating direction molded into them, otherwise you can verify if it’s correct by looking at the position of the inlet to the evaporator.

 

Try switching from fresh air to recycle inside air. If volume of air goes up while on recycle then goes down on fresh air. Check for debris under windshield wiper transmission cover. Fresh air intake is usually opposite side of wiper transmission. Common for them to plug with dirt leaves and small twig's. Debris holds moisture and can freeze in winter or while AC is running blocking air flow completely. Default when heat or ac is on is fresh air on start-up. Also if it's an ac issue could be over charge on freon. To much freon causes evaporator to freeze. And ac runs even when heater is on to help dry the air and reduce window fogging. Low freon can also cause same issue check pressure on both high and low side.


Good luck
Old school tuner

 

all air must go thru the evaporator so get an inspection borescope and check it out. could be a mouse nest if you live in the country