I was driving along when I noticed all the dash warning
lights flash on, a few days later they did it again I
noticed that they went through the same cycle as when
starting the car next time while driving the whole dash went dead and stayed so until I restarted the car.
Eventually the dash stayed dead so I have replaced it with a good unit (out of a 1994 4.0l) from EBay now the speedo does not work the rev counter only works up to 3000rpm.
The fuel gauge only reads half full when the tank is full but all other instruments and warning lights work as normal.
I have a 1994 Jaguar 4.0l sovereign vin69**** are there different instrument modules for that year? have I bought a bad module?
Has anyone the wiring info for this model's
instrument plugs?
I know the speed sensor is ok because the gearbox locks up at 50mph as normal
Peter

 

Hi All

This instrument module is finally fixed, having bought a spare which did not work properly I decided to
check the differences with a voltmeter, first I removed my module then removed the shroud from
the instruments pack(4 screws). Then the back panels from each module to expose the printed
circuit boards, next I refitted the original instruments in the car,(on this module nothing works)
and switched on the ignition.
I assumed that there is an open circuit somewhere, so for simplicity I picked
the two large blue axial capacitors and checked voltage at the positive end of both, one had battery voltage
the other had 6 volts aha!. next I swapped instruments (on this module all warning lamps work normally
the fuel gauge and rev counter works partially the speedo does not work) and again checked the blue
capacitors at positive terminals both had battery voltage Eureka!!! Swapped over instruments again and
fitted a jumper cable to link both positive terminals and the instruments came to life and all was working
although my finger holding the jumper in place got a bit warm!. Next I removed both printed circuit
boards from the instruments then placed a large plastic bag over the hole in the car dashboard area,
and through 2 holes I had made in the bag pulled the wiring plugs (this for safety). and connected
the original circuit board back into place.
Now it was a simple matter of tracing the circuit from the capacitor positive terminal back to the
power input at the smaller plug fitted at lefthand end viewed from drivers seat.
(with lights off and key to ignition-on there are only 2 terminals live ) I was looking for a component with
batt volts on one terminal and 6 volt at the other(the IC chips where beyond my capabilities to test so
were ignored) the first was marked R100 so was swapped no good, the next was marked 1N4 004 when I
swapped it out I had batt volts at both pos terminals on the blue capacitors, I rebuilt the module and
refitted it into the car and all is good.
This required patience and perseverance swapping PCB's after each test took time,
I also started as close as I could to the source of power to the board.
The faulty part is marked 1N4-004 and I think is a diode.
Look here for module removal instructions
Peter