in case it helps anyone the white/ brown wire to the timer /relay is the earth from the dash warning light . if u suspect the bulb has gone , with the ignition turned on and this wire earthed out the bulb should be lit . this is easier than taking out the instrument panel to find out if the bulb has blown ! but if it has then its to come out anyway.
just converted my v8 to tdi when i wired in the heater relay the warning light wouldn,t light . this is because the v8 loom doesn,t have a wire from the warning light to the heater relay . as i had a spare loom to butcher i removed a connecter from the instrument multi plug and put it into my v8 multi plug (i think it was terminal 5 on the plug , this gave me the wire i needed to make the warning light come on ) connect this to the white /brown wire on the relay. connect the relay white wire to ignition live i used the original coil feed wire which i have also used for the fuel shut off. connect the relay white/ red wire to the white /red on the starter motor . i had 2 white/reds in a connecter of there own when i traced them thru the harness they both join together and go to the starter , i split them and used one of these . u could run a wire direct to the starter but my way looks a lot neater. the black wire from the relay just needs to go to an earth point . the thick brown to battery positive and the thick black/yellow to the heater plugs . it all now works as it should and the warning light comes on when the key is turned stays on for around 5 seconds then goes out the relay is still on for around another 10 seconds before switching off. hope this helps someone out . of corse u can make the heaters work without the warning lamp but i wanted mine to work and be a tidy job when finished. no ugly wiring under the bonnet . nothing to give it away that its not a factory fitted tdi . steve.