WMR-968 Weather Station RS232 problem

[davidc]

I'm trying to tidy the connection between my PC and an Oregon Scientific WMR-968 Weather Station. I would like to move the power adator to be next to the PC and feed the 12v down the RS232 cable alongside the signal then at the weatherstation split it out back to the power socket. It only takes a few mA so no problem using Cat5.

I thought it would be easy and the weatherstation would only need pins 2 3 and 7 connected (or 3 2 and 5 as it is 9 pin) and I could then feed the power over say pins 8 and 9 but it doesn't work.
Do I maybe need to link some other pins together at either the PC or Weatherstation ends ? Or maybe use different pins for the 12v ?

Someone else must have done this ?