Ac/heater

[staruser]

I have an '83 Chevy S10 Tahoe that the ac and heater control aren't working correctly. The fan turns on at all speeds, but won't change from the defroster mode. The control switch works fine, but just won't go out of defrost. Checked voltages and getting power where needed. Found that there is no vacuum. I can't find where the vacuum line runs through the firewall and connects to the engine. Can anyone help me?

[ryank1]

Usally on these trucks the problem is in the vacuum line that attaches to the vacuum ball under the hood.

[staruser]

Getting vacuum through the large tube and vacuum from the small side of the vacuum ball. I can blow freely through the small tube as well as sucking without any pressure.