the resistance section of a mechanical VOM? If you have a digital meter and are using the diode check function you will see OL one way and .6 - .8 V developed across the diode IF you have been able to disconnect one end of the diode from the black wire (grd) or the yellow (relay power side of motor and input port in the control box) wire. If using an older VOM on a X10 range you should get 10 times the resistance one way against the opposite lead connection to a diode which is isolated on one side from it's circuits.
My book shows that when the engine is started the pump will try to make 180 bar of pressure if it sees 140 bar or lower. This takes 10 - 15 seconds. This will power the pump as in your scenario and if the spike suppression diode is shorted it will take out the fuse F1. Check the diode, don't run it without the diode in circuit as it protects the controller from collapsing field pulses when the motor shuts off. If its shorted there won't be a pulse in the field windings but if it is not there ( or open) there is nothing to stop the pulse from finding the electronics in the controller.


In you #1 statement you say that a fuse which normally blows does not blow as ign is turned on IF the Mst.Cyl/Pump is disconnected and you are lead to believe the pump is ok. I say the device which is disconnected is suspect if the safety device is not harmed as it is not a factor of electrical load to the fuse anymore.

Then in your #3 statement you have the pump connected, the fuse blows. You need to pull the pump relay to isolate the field windings and the diode from the circuit. The connectors won't do it.

posted by 12.221.113...

• Baffling ABS fuse problem / diode OK (long), Graham, Sat, 13 Sep 2003 14:35:47
  • Graham, are you using the diode check function or, Lu, Sat, 13 Sep 2003 19:06:40 <-- Viewing This Message
    • followup question for Lu, Graham, Sun, 14 Sep 2003 05:50:19
      • In the 93 book there are listings for ABS Mk IV,, Lu, Sun, 14 Sep 2003 10:13:08
        • Re:more for Lu -- which do I have, Graham, Sun, 14 Sep 2003 16:18:42
          • Ya can't test anything while its in circuit., Lu, Mon, 15 Sep 2003 18:51:25
  • one more thing, Graham, Sat, 13 Sep 2003 14:38:48

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