Touran T1 P1503 Alternator Term. DF Implausible: Fan worn through loom

[VAG-Abound]

For as long as I can recall a VCDS scan of out 53 plate Touran would show:

17911 - Load Signal from Alternator Term. DF
P1503 - 000 - Implausible Signal

Although I haven't noticed any ill effects from this I thought it was time to fix it as a part of general efforts to maximise battery health.

According to the wiring diagrams the signal is carried via a short loom from the control board in the alternator to connection point on left of engine bay, then from there to the supply control unit in plenum chamber under windscreen.

I'd expected to find a problem in the initial short loom, thinking that this was the harsher part of the environment. The 4-way end-point connector for this took a bit of finding as it wasn't as far left as the diagrams I'd seen suggested. It was more in front of the gearbox than left of engine bay. I was a bit surprised to find continuity on both the wires from the 2-pin alternator connector to the right pair of pins in the 4. There were signs of chaffing on the insulation of the wires, but no copper that I could see. Despite this I convinced myself it might be worn through more than I could see and was grounding itself, leading to the error code. I rerouted the loom a bit to try and reduce the chaffing, and hopefully prevent the assumed grounding.

Because the intermediate connector was now in a different place I checked the revised route of the 2nd half of the circuit and I realised it was perilously close to the radiator fan housing. And while trying to fix that I saw that it had already been on that route, and had been badly worn by rubbing from the fan. The outer sleeve had a patch missing, and the wires inside looked messy.



After removing air-box I was able to remove a couple of cable clips and lift that half of the loom into daylight and remove the wires from the plug housing to see things more clearly. One wire OK, 2 badly chaffed but looking OK electrically and one severed - not surprisingly the DF terminal one.


Fix was wrap the two worn ones in a strip of insulation tap, and use a small heat-shrink crimp on the broken one by just stripping the damaged ends to maintain as much length as possible.


Then a length of heatshrink over the 4 loose wires all to replace the shroud I'd cut away, a few wraps of insulation tape over the old / new shroud join, and reloading of the plug.

I then moved the loom support / carrier that was too close to the fan, re-clipped everything in place. Job done, fault cleared and hopefully won't return.