The infamous APC clicking - Saab 900 Bulletin Board - Saabnet.com
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Your clicking symptoms are typically at the SAAB 900 APC system's solenoid valve(BCV/Boost Control Valve), which should be mounted at the radiator support.
This solenoid will typically cycle, in the manner mentioned, when the APC control unit is not receiving proper input signals, or could be indicative of a tired APC component. Many of the 900 APC systems have been in service for over 30 years, making a common culprit of a cycling APC solenoid valve to be determined as weakened terminal connections at the APC control unit or components. Clean all terminal connections at the APC control unit wiring harness, and APC Knock Sensor, which will be mounted at the engine block casting and may be viewed through the B202 engine's intake manifold plenum center. A firm copper wire brush would allow for cleaning the terminals, and look for obvious oxidation which may require additional effort.
In some cases, faulty APC components, could cause similar solenoid activity, and the most common culprit would be a Pressure Transducer which may be found under the 900 interior knee shield. Also, check the engine compartment for vacuum line leaks which could lead to a reduction of engine vacuum and cause similar APC solenoid symptoms. In some rare cases, the APC control unit, could prove as being temperamental, and your symptoms will subside, if installing a known good replacement control unit. Any 1986 to 1993 900 Turbo model APC control unit will allow for direct installation for testing.
Good luck with your repair, and we will look forward to hearing relative to any progress!
Gary K. at SWEDISH DYNAMICS, INC.
->Posting last edited on Tue, 22 May 2018 21:24:19.
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