I just fitted an oil pressure gauge to my VT and it has a weird problem. With any electrical load the oil pressure reading on the gauge goes down. For example with the car idling and everything off it sits at about 53PSI. If I turn on the headlights it will drop to about 45, put on the high beams 30 and with the heater fan on you can get it to 0 PSI. What would be things I should check, possible causes?