After a battery replacement I still appear to be getting battery drain. What I have discovered is that there’s an aftermarket button I need to press to warm the glow plugs which seems to run directly from the battery terminal. Even with the ignition off and the isolator switch active the glow plug warmer still lights up when pressed indicating its constantly live. So two questions, on a 300 tdi engine on a 1990 defender 90 do I need to heat the glow plugs to help starting? Can I connect to a live source other than direct to the battery or is there a high load on the glow plug heater? Thanks