Hi Guys, this hopefully will save some of you some money in the
future and sa few of those charging problems
The Load Dump Module was responsible for a charging problem, where
the alternator had been checked and was OK, and the battery was
brand new. The car would run for about 3 hours and then stop,
battery dead, no charge from the alternaotor, battery charge
warning light on throughout the whole event. Charge battery
overnight, car would start and run again for about 3 hours on the
battery until dead again.
After a lot of searching the archives and checking connections
etc.etc it was time to open up the load dump module. It basically
contains 2 resistors, 2 diodes and a capacitor. The main purpose is
to protect the electrics from overvoltage spikes, but it also
supplies a battery monitor voltage to the alternator and controls
the warning light. It’s 12v supply is taken from Fuse 1 in the
centre console ( shared with some light modules ) which when
removed or fails stops the charging and puts up the warning light.
Anyway, in my case one of the diodes in the module had failed and
gone short circuit, pulling down the battery monitor feed back to
the alternator and switching off the regulator in the alternator,
causing the symptoms mentioned above.
The whole module can be rebuilt or repaired easily with parts from
your local electronics store for about $10. Jaguar charge $400 for
this module !! It’s a small single sided circuit board and easy to
A word of warning though. The Haines manual shows a schematic of
the load dump module which is not accurate in section 5. They have
a short circuit shown accross the 2 diodes which should not be
there. ( it wouldn’t work with the short circuit added anyway )
Also the circuit diagram in section 12 is wrong. It shows 2 wires
going to the alternator, when actually one of them goes to ground,
and the diode shown in the feed from the fuse is back to front.
I have seen threads to charging problems, and maybe this will help
some of the ‘lost souls’ who have just about given up.
Good luck guys.
89 Soevereign 3.6.–
avoca beach, Australia
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