The air conditioning idle-up system is used to increase engine idle rpm any time the air conditioning compressor is in operation. The system shown is used on D type EFI applications where the ECU controlled Idle Speed Control Valve (ISCV) does not have an A/C idle-up feature. This system maintains engine idle stability during periods of A/C compressor operation. Additionally, it keeps compressor speed sufficiently high to ensure adequate cooling capacity at idle speed.
The A/C idle-up system consists of an A/C amplifier controlled Vacuum Switching Valve (VSV) and an Air Switching Valve (ASV) or actuator. By applying vacuum to the ASV diaphragm, fresh air from the air cleaner is by-passed into the intake manifold, increasing engine rpm.
When the VSV is energized, a manifold vacuum signal is applied to the actuator diaphragm of the ASV causing it to open the passage between the fresh air supply and the intake manifold. This extra air introduced directly into the intake manifold causes engine rpm to increase.
When the VSV is de-energized, the vacuum control signal to the ASV is blocked and any trapped vacuum is bled off of the diaphragm. This causes the ASV to block air flowing to the intake manifold, decreasing rpm.
The A/C idle-up system described above is not an ECU controlled system. For information on ECU controlled ISCV systems which control A/C idle-up speed, refer to "Engine Controls - Idle Speed Control Systems."
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