GMC Repair: 1993 Safari vacuum, vacuum line, safari van

Question
I have no vacuum to the heater/ac control on my 93 Safari van. I can't seem to trace the vacuum line through the dash to the engine.

Answer
Look up along top of the firewall behind or INSIDE of the wiring harness. The vacuum line in the engine compartment is usually a smaller diameter black PLASTIC line vs a rubber line.

Look near where all the wires pass thru the firewall.

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