I am not sure if the ’52 is the same as the ’55 but for my ’55 L15, the gauge resistance between B and T is 60 ohms, between T and earth (case) is 100 ohms. The sender varies between 0 and 86 ohms. If the sender is erratic, open it up and clean the sliding contact.and the coiled wire.
When the tank is full it should read high and, when empty, it should read about zero.
Also, make sure that you have an effective earth on the sender. Don’t rely on connecting it to the tank.
Roger Grix