F 350 2WD Pickup V8-351 5.8L VIN H 4-bbl HP (1985)
Barometric Pressure Switch: Description and Operation
Fig. 19 Ignition barometric pressure switch. 1984-87
1984---87
This switch, Fig. 19, controls spark timing and/or other electrical devices according to barometric pressure changes. Calibration resistors in the switch
assembly cause the ignition module to vary the spark timing. Spark timing is advanced for vehicle operation above a predetermined altitude and retarded
for vehicle operation below a predetermined altitude. Some switch assemblies control both spark timing and another device while other switch
assemblies control only one or the other.
