F 150 2WD Pickup L6-300 4.9L VIN E 1-bbl (1982)
Vacuum Reservoir HVAC: Description and Operation
Fig. 37 Vacuum reservoirs
The vacuum reservoir, Fig. 37, used on some vehicles, acts as an accumulator and prevents sudden drops or rapid fluctuations in a vacuum signal during
acceleration. If vacuum in the reservoir leaks more than 1/2 inch Hg in 1 minute, the reservoir is defective and must be replaced.