Fourtrak 4WD selecton electrical problem


My 1999 Fourtrak 2.8 TDX will not select 4WD when hot. Its an electrical problem.

Same problem for 4H or 2L selection, you can hear the relay click, and if left selected the relay gets warm, but no green light on the dash and physically 4WD is not engaged.

It works normally fist thing when the vehicle is cold !

I have eliminated the usual vacuum switches, the switch on the gearbox, and the switch on the dash, all are fine.
I have not tried a replacement relay because it testeed as functionally OK.

The nearest I have got to further defining the problem is there is a fine green wire in the loom ( exposed on the bulkhead connecting block ) that takes an earth to the gearbox switch , this seems to "loose its earth " ( tested at the gearbox end ) when the malfunction happens...but I cannot trace this wire from the other side of the bulkhead connection to where it ends up " under the dash "
Has anyone else experienced this one please , or anyone with a detailed wiring diagram that tells me where this green wire ends up Unknw ......or any other ideas would be greatly appreciated . ( BTW its been a pain not being able to use Rocky in the snow where it always excelled !!! )