Control for the air delivery mode is not working on my Blazer 98 4WD.

Blower motor, fan control and temperature is working but air will come primarily from the instrument panel vents.

Heater, blend and defrost are not working. I've changed the complete comfort panel, which includes the mode control, but it is still not working...

Thank you for your support!

 

Manual HVAC or automatic climate control?

 

sounds like a disconnected vacuum line to me

 

I've a manual HVAC climate control built-in.

 

Please how I can fix that...Thanks.

 

check vacuum lines under hood, there should be one going to a hard plastic tube bundled with wires going into the firewall under the cruise control module (drivers side corner). It could be disconnected, or not correctly hooked up.

 

Right in the same area the vac hose that goes to the firewall there is a three way splitter on the lines, there is usually one really short piece of tube that wears out really quick, check it for any cracks. Basically if you touch the line and it instantly turns your hand completely black, it's time to replace the lines.

If this isn't your problem, then you might have to pull the dash and check for vaccuum at the controls.

 

I've now changed the vacuum lines, but I just can not find the connection of one of the vacuum lines under the cruise control module.
Please see attached photo with yellow arrow.

 

https://blazerforum.com/forum/2nd-ge...nnected-82106/

 

Thank you very much for the tips! I've replaced the vacuum lines and it works now.