HVAC airflow from h-c ??

[Matp1992]

Hello , ‘92 RCLB 4x4 (7200gvw) here . I have an air flow issue when switching from hot to cold and vice versa . Everything works as it should the floor ,def , and vents all switch as they should and the fan switches from L,M,H as it should . The issue is when it’s over on the cold side I get perfect air flow through the dash but when switching to hot the air flow reduces prob 85-90%, switch it back to cold and the air is back full blast . I’ve tried every combination and blowed the ducts out with air and even ran a small vac hose through the places that was accessible. Any input would be appreciated on this .

 

[GoToGuy]

So airflow is reduced. Determine if fan actually slowing down? Is the air control valve fully changing positions? Remove fan inspect inside duct to see if heater exchanger is full of " fuzz, dog hair, plant matter, grass, seeds, pine cones, corn, miscellaneous stuff." It can get clogged just like a radiator.

 

[Matp1992]

Found it (gross)

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[ChRoNo16]

How did you get that bottom part off and what tools did you use?

 

[Matp1992]

Several little 7mm screws, one is kinda a pain to get too . I still have it all apart , when I get home I’ll take a pic of that bottom lid so you can see where they are exactly located . Took literally 10min to get the heater core out . It’s a great design compared to others

 

[GoToGuy]

What make, year, model ? Is that the cabin filter?

 

[Matp1992]

That’s

What make, year, model ? Is that the cabin filter?

Chevrolet ,1992 , Silverado . Rats nest on the fan side of the heater core that’s why I had almost zero airflow on the hot side

 

[GoToGuy]

Got it, at first it looked like a filter. I did inspection for a large dealership , used, leased turn ins. If you can dream it , it finds its way to the fan filter area, as the heat / cooling exchangers are also filter screens.

 

[Matp1992]

How did you get that bottom part off and what tools did you use?

Ok here’s the bottom of the heater box that houses the heater core . The red arrows are the screws that can be accessed very easily and the blue one is between heater box and floor board area , you can’t see it with eyes but you can feel it and it takes a 7mm deep well with a little extension , using Channel locks to turn it a couple times then You can turn the socket with your fingers to remove it . It wasn’t hard just took a little fiddling around (going back together may be a little tougher).

 

[GoToGuy]

Looks like the forum brain didn't like your photos