Message text written by "Michael D. Porter"
>The diodes seem to be the weak link in the headlight operating
circuit, thanks to Lucas providing diodes of substandard reverse current
capacity. My guess would be that the diodes have a rating of about 50PIV
(peak inverse voltage), and that rating is not sufficient to withstand
the back emf created when one operates the motors by hand without first
disconnecting the motor harness.
<
Michael,
Only Superman or Steve Austin (Lee Majors not the wrestler) could turn the
motor by hand fast enough to generate that kind of back EMF. Besides the
diodes are not even in the same circuit as the motors. The diodes are in
the circuit with the coils of the relays that run the motors. What is
causing the diodes to fail (unless it is an intermittant short to ground)
is the voltage spike from the relay coil (which is inductive) when the
limit switch opens.
Nonetheless, when 400 volt diodes are as cheap as anything you can buy, why
use 50?
Dave
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