CITROEN XM - Electro-Valve Diagnostic

Suspension 64 Electro-valve diagnostic
92 Citroen XM Internet Reference Version 1.0
3/3/99
64 Electro-valve diagnostic
Andy Burnett supplied a serviceable ECU which when commented to my car resulted in the car
changing immediately to AUTO. Changing back resulted in a rapid return to permanent Sports mode.
This was good enough proof for me but Andy suggested I run with it for a few days in case it was the
electro valve that was the culprit The car was sheer luxury to drive but my good lady threatened me with
dire consequences if I even looked at the selector switch and so it remains AUTO selected to this day.
Diagnostic light
Thanking Andy profusely I now started work on his suggestion of fitting a diagnostic lamp wired to the
electro valve to allow the driver to observe when the electro valve was energised (Soft) and
De-energised (Sport). This would indicate when each sensor was operated and would be an extremely
helpful device for future fault finding. A simple enough job with cable entry to the car being the most
difficult and as this was going to be a permanent fitment I positioned the lamp and bracket m the
aperture below the radio. It's cheeper then a CD player and more useful. Remember, the operating
voltage of the electro valve is 5- 6 volts but a 12 volt indicating bulb will give adequate illumination.
Checking the ECU for faults
The old ECU was opened and the circuit board removed for examination under am illuminated bench
magnifying glass. No visible damage to components was evident but a few suspected dry soldered
joints were noticed, one very bad with a component (resistor) actually loose. I passed the board to an
electronic friend of mine who examined, confirmed, removed the protective varnish and resoldered the
offending joints. As a born optimist he informed me that everything would, not should, work correctly
again. This I will try sometime m the distant future when I feel confident enough but it would be ironic if
this was the answer to all our problems DRY JOINTS.
(Thanks to Jim Davidson and the CCC)