My 98 Tahoe only blows air from the defrost vents..No Hot No Cold, just air.

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Bamba

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Hi guys my Tahoe only blows air from the defrost vents. It doesn't seem to blow Hot nor Cold air, just air. None of the selector positions (Floor..Mid-Level, or Top) seem to be working.

Any help diagnosing my problem will be appreciated.

Thanks in advance

Bamba
 

east302

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There are two actuators that control air and temperature. One is by the gas pedal and controls floor-dash-defrost. One is behind the ashtray and is for temperature.

There is a silver position indicator dial with marks in the plastic next to it. Adjust the vent position dial and watch the dial. It should rotate between those two marks (roughly 11 to 1 o’clock).

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The same goes for the temperature dial but it’s harder to see. Pull the glovebox and look behind the ashtray (sort of).

See what those dials do.

If they don’t move at all, unplug the connector and there are three wires in it. One is ground, one is battery (12V or so) and the third is a signal wire coming from the dash control panel.

I forget which is which, but you’ll put a meter to the ground pin and the other to the battery and then the signal wires. Make sure you have 12V on the battery one and then adjust the dial and see what the signal wire voltage does. It should vary noticeably - maybe 1 to 12 volts if memory serves.

If the voltage doesn’t change, then the panel isn’t sending a signal and would be what I would replace. Well, at least the signal isn’t getting to the actuator connector so rule out a damaged wire or issue at the connector at the panel side before you condemn the panel.

I’d skip the Dorman version of the a/c panel. I had one that nearly caught on fire. Delco makes one that is a reasonable approximation of the original.

If the voltages are correct and the dial either doesn’t move or moves erratically, then I’d swap out the actuator. One or more of the internal plastic gears are likely cracked; you can open it up to confirm. Less likely, the damper has become dislodged in the box so you’d pull the actuator off and see how well the damper arm rotates. There should be no up/down/left/right movement. It should just rotate.

The actuator shaft is keyed, so it only goes on one way. Rotate the damper to align it with the actuator (don’t try to turn the actuator to align with the damper). The center 12 o’clock mark on the dial actuator corresponds to a 12 o’clock position on the panel dial.

Also, on that mode actuator (gas pedal) - make sure that the linkage arms are intact:

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