I have a '89 Mercury Grand Marquis that has a gas gauge that doesn't work. The gauge is way past empty and the low fuel light is always on. I checked power and ground to the sending unit and they seem to be OK. I say "OK" because when I put my testlight to the power to the sending unit the light slowly pulsates (kinda of like a strobe light on a low setting). Is this normal for this type of vehicle? I also checked the resistance at the sending unit it came out to be 70 Ohms. I'm thinking it is the sending unit that is bad. I think it is stuck in one position.