mikeThanks Raul, I had a feeling it would be of that order! orange 0.5mm no chance!Depending on the glow plug setting can be 80-90-100w plus the fan. My plug is on 90w setting, plus the fan speeding up on start up, it draws about 100-110w increasing to max 135w. At 13,2v that’s about 10,2A. The heater original harness comes in 2,5mm2 for the main feed. To that point is fed by 4mm2 with 15A fuse.
With a 0,5mm I think it will fail to start due to low voltage.