VDO tachometer-hourmeter with bad display

[Dino]

Tachometer - hourmeter VDO N02-070-109
The RPM portion is OK while the hourmeter LCD display has a
random problem, most of the time is blank, occasionally
shows flickering numbers while rarely shows a correct
number. The counter seems to increase correctly
I've disassembled and cleaned and would like to test it, but
the VDO site do not contains documentation for obsolete
items.
The rear has 4+1 faston connectors ( + / - / S+ / S- / ?).
Connecting 12V to + and - point the display stay blank.
Hany suggestion or link?
Thanks Dino

 

[Dino]

<http://www.ybw.com/forums/showpost.php?p=2693853&postcount=10>

Thaks for the link.

The above link do not show any details about wiring
connection.

I have decided to progress with a separate hourmeter and
leave the original tachometer only for the RPM display.

The reason is because of the uncertainty of hourmeter
connection. The VDO is connected to the motor with two wires
that carry the RPM pulse. It is my believe that RPM pulses
are internally analyzed to originate the "motor running"
information to the original hourmeter.

I'm progressing with a mechanical 12V hourmeter and a small
12V relay connected to the alternator output.

 

[Dino]

Why not just wire it directly to the "ignition switch"? When the
switch is on the hour meter runs, when it is off it doesn't.
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

My design is based on a real "motor running" hourmetering,
while, your proposal is to consider the "power to the
engine" equal to "engine running", that is almost true.

I've been captured by VDO electronic design, and lost the
practical side of the problem.
Thanks
Dino