Vauxhall Workshop Service and Repair Manuals

Diode, Check  

Circuit diagram of an electronically-regulated alternator  

 

1  Rectifier diodes   2  Excitation diodes   3  Stator winding   4  Excitation winding   5  Integrated electronic voltage regulator   6  Battery   7  Ignition lock   8  Charge telltale   9  Charge telltale relay     A defective diode can be detected from peaks or troughs in the voltage wave on the oscillogramme. On a removed diode plate, correct functioning of the diodes can be determined using a diode tester, ohmmeter or test circuit with checking lamp.     Important!    The test voltage must not exceed 24 V.   If diodes are faulty, replace diode bridge completely.

  Inspect   

Check negative diodes (1) individually.   Negative diodes have passage from housing to connection and block in the opposite direction.   Hold positive test probe (2) to diode plate and test probe (3) to diode connection.   Test lamp must illuminate. Exchange test probes and contact again. Test lamp must not illuminate. If diodes are faulty, replace diode bridge completely.

Check positive diodes (1) individually.   Positive diodes have passage from connection to housing and block in the opposite direction.   Hold positive test probe (2) to diode connection and test probe (3) to diode plate.   Test lamp must illuminate. Exchange test probes and contact again. Test lamp must not illuminate. If diodes are faulty, replace diode bridge completely.

  Inspect   

Check excitation diodes (1) individually.   Excitation diodes have passage from long to short diode connection.   Hold positive test probe (2) to long diode connection and test probe (3) to short diode connection. Test lamp must illuminate. Exchange test probes and contact again. Test lamp must not illuminate.   If diodes are faulty, replace diode bridge completely.

  Measure   

Check carbon brushes for wear.   If carbon brushes are worn down to dimension "I" = 14 mm/0.55 in., replace carbon brush holder.     Inspect    Check that new carbon brushes can move easily in brush holders.