A/C only blowing a whisper... sometimes

GMT400’s are famous for the blend doors getting stuck. My 97 has most of the air trapped in the dash. Especially when settings is on the upper person (all the way to the left).

Try changing your air setting to floor or defrost and see if the air comes out full force vs the dash setting.

If I hit a decent bump occasionally I will hear a light clunk and all of the sudden my dash air vents blow full force. I can tell when it’s not full force because the air won’t even reach the front seat backs. When it’s working properly you will feel air move well past the front seat backs.

I’ve been twisted into a pretzel with my hand up through the middle floor exit and have pulled the entire middle blend door out. The rubber seals were Disintegrated but the motor actuator by the accelerator pedal is working correctly.

Problem is when you turn truck or blower off all the blend doors move to the heater floor setting. So if you are lucky to get it at full force, next time you start truck or turn blower on it will probably get stuck again.

If you figure out a solution let me know!

I think mine is always mixing in some hot air. One of these days I will list shut the coolant off to the heater core.

454cid said:

I think mine is always mixing in some hot air. One of these days I will list shut the coolant off to the heater core.

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Aren’t you up north somewhere, lol?

east302 said:

Aren’t you up north somewhere, lol?

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Hey, it's not cold alllll year, in MI!

yes if the resistor itself fails then its all or nothing, but that corrosion in the picture could easily cause intermittent lack of continuity across the resistor coils. Those are only crimped connections on the resistor coils. You may have other problems but unless you change that blower resistor you could end up chasing ghosts.
Also that additional resistance can or already is causing problems with your AC/heater control panel. Much more expensive to replace.

I recently replaced my blower motor and resistor this past summer but this morning (5am) going to work the defrost is not blowing. I have venting coming out the floor vents and when selected,the dash vents work fine. Winter is coming! Please help!

Perhaps the air door actuator for defrost isn't working.

Defrost is the default position, they want you to be able to clear the windshield even if you're not "comfortable". So for the defrost to not work right, something is very wrong.

Yes its the Actuator Mode motor. I found it's not rotating enough to move the doors. There is another thread "Blend door Actuator" with some photos and parts. Thanks.