My Alero AC airflow switch for the air/heater does not work for the Vent setting, only the mixed and above. What is the cause of this, what part needs to be replaced and how easy is it to replace?

My mom had a similar issue in her 99 Blazer. In the Blazer, a vaccuum hosed controlled the airflow and one of the hoses had a hole in it. I'm not sure if the Aleros use the same system though. The stealership charged $86 to get behind the dash and replace the hose.

- Jeremy

You here any hissing in the dash whenyou flip through the selections?

probly do hav a vacum line loose or broken behind the unit in the dash.

What engine is this?

Needless to say the Alero uses engine vacuum to operate HVAC controls. Classic symptom is air at defrost or bottom vents but none at middle vents.

Remember the source of the accessory vacuum line feeding HVAC controls is at the intake manifold. The line is normally white in color. On a 3.4L it is located at the left hand side (driver's) of the upper intake manifold by the fuel pressure regulator, front fuel injector rail. So check it first. From there it feeds into the main wiring harness going into the firewall and to the dash.

YA, that vacuum line feeding HVAC controls gets broken/smashed pretty easy.
Especially when you are or hav been working on the ignition/plug-wires.
I try not to rest my arm(s) on the top of the motor anymore :nono:

YA, that vacuum line feeding HVAC controls gets broken/smashed pretty easy.
Especially when you are or hav been working on the ignition/plug-wires.
I try not to rest my arm(s) on the top of the motor anymore :nono:

Yeah Xero, I remembered it when my son and I forgot to plug it in after doing the UIM exchange. When he took it out for a test drive he came back asking WTF happened to his A/C?

BTW - Where is that UIM vacuum line on the 2.4L and 2.2L Ecotec?

BTW - Where is that UIM vacuum line on the 2.4L and 2.2L Ecotec?


If I'm not mistaken it runs on the driverside top of the motor(kinda like the 3.1-3.4) but I think it varies from year to year which Plastic loom they run it through.
Most of the time its on the left side(drivers side) of the intake, which would be on the right side to the TB facing the engine.

I very seldom work on 2.2's-2.4's , just get lucky I guess.
Most of them that I hav worked on,
was because of broken spark plugs, head work, ignition troubles,
and or timming chain(s), the typical 4cylinder things :)