I fitted Spal 11 inch fan a few years ago to replace original aux fan. Spal would cut in correctly and then out after around 10 seconds. This is using Spal wiring but connecting into wire to sensor on water pump. The problem was found to be earth going back to jaguar diode so earthed wire direct to bodywork. All fine for 2 years and last year problem started again. As the fan cuts in at correct temperature I think unlikely to be sensor. Occasionally it will cut back in but not often. Any ideas of where problem could lie?