Vacuum Switches
Two vacuum switches are used to determine throttle position. A ported vacuum switch is used in conjunction with a manifold vacuum switch. The Open Loop-3 (at idle) vacuum switch (red) has normally closed electrical contacts which are opened by 3 ± 0.5 in. Hg vacuum. The Open Loop-2 (wide open throttle) manifold vacuum switch (blue) has normally closed electrical contacts which are opened by 4 ± 0.5 in. Hg vacuum.
A second manifold vacuum switch is used in conjunction with a coolant temperature override (CTO) switch to signal engine starting position or cold operation. The Open Loop-1 (cold operation/engine starting) manifold vacuum switch (yellow) has normally open contacts which are closed by 3 ± 0.5 in. Hg vacuum. All vacuum switches are mounted together on left inner fender panel.