I want to check the accuracy of my gauge. There is like 3 gallons in the tank and haven been completely filled. On a 71 RR, can the sender be checked with it in the car or do I have to drop the tank and pull it out? It should read 73 ohms + or - 12 ohms empty. Full should read like 9.6 + or - 1, is that correct? Thanks in advance on info