Despite its fancy name the overvoltage protection relay is basically for your purposes just a power supply relay. Since it would kill the Lambda control module I would verify that the frequency valve is buzzing (this is a device that looks like an electric injector, it sits longitudinally beside the airflow meter on the drivers side). This will confirm that the control unit is powered. If it it is powered then the likelyhood is that the idle control unit also is being powered.

The idle control units are bad about cold solder joints on the PC board. We fix 3 out of 4 that are bad by resoldering the PC board. BTW both sides of the idle valve are connected to the controller. Any power at either side would indicate that the controller is being powered.


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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by Webmaster (edited 03-14-2000).]