Henry...Good Lord! $180.00 ? Really?...Try this before you buy anything. First of all make sure that there is a complete circuit between the fuel gauge and the sending unit. Disconnect the hot wire at the sending unit and touch it to the body metal while the ignition key is turned on. As you do so have a friend look at the gauge and sing out if it springs to life. The idea here is only to see that there is somebody home in the gauge department, not to try to peg the gauge out. If the gauge doesn't move, you have either an open circuit to the gauge or the gauge itself is bad. Either case is another story. If the gauge moves, go on and remove the tank unit. Hold the sending unit up with some back lighting for the float. If the float doesn't have fluid in it, most likely the fault lies in the fine copper wire winding. You can even go to the trouble of rigging up some jumper wires so that you can hold the sending unit in the right attitude and move the float lever up and down while your friend observes the gauge if you want to, but that really isn't necessary. The sending unit acts like a rheostat with a blade contact brushing progressively over the fine wire winding with the resultant variation in resistance being indicated as a change in fuel level in the tank. Usually the fine wire will break near one end of it's travel. If you must you can use an ohm meter to confirm that there is an "open" in this winding circuit. Visually locate the break and if needed, carefully uncoil a turn or two until the end can be brought into contact with the next soldered connection or the other broken end. The idea is to get the wire just long enough to work with but to disturb as little of the coiling as possible. Wash the whole thing in alcohol and let it stand for fifteen minutes to allow the alcohol to evaporate. Use a low temp soldering iron and solder to make a new connection. Don't worry too much about changing the accuracy of the sending unit by changing the number of coils and so the resistance. I don't think that I have EVER seen an accurate sending unit/fuel guage on a Volvo. Stuff everything back together and see if the gauge works. You can easily reschedule your understanding of what the gauge really means when it says "half full" by topping up the tank and driving about 150 miles and topping it off again. If the gauge said half full and you put in about 7 or 8 gallons, since the tank holds about 15 gallons the gauge would be roughly correct. You do the math if it varies too much one way or the other. In any event you'll be back on track in about 2 tanks.