BMW Repair: Fuel guage faulty reading !!!, fuel level sensor, cigarette lighter

Question
Hey Tino, I recently bought a 1997 BMW 318SE and have been having a few problems !!! Last week all the lights went out on the instrument panel and switches and at night i couldn't see what speed i was doing ? So I consulted my hayes manual and it pointed me to my 318 fusebox to change fuse 37 ... which i did and it worked !!! So that problem solved but about a day later after filling my petrol tank and hoping back into my car and starting my engine i noticed my fuel guage was reading empty and the orange light glowing !!! Now when I Bought the 318 this was one of the problems the mechanic had to fix before i could take my baby home !! So when I went to the garage to pick it up I could see him in the back with the seat removed i think he was replacing the Fuel guage sender unit cause in the hayes manual it pointing me to that ? only guessing now !!! So my question is did I do something when I changed Fuses ? only touched 37 or could it be something else ? Your help greatly appreciated !!!

Answer
Hi Westly,
You have not done anything wrong to the fuel gauge circuit when you replaced Fuse 37 for it is only concerned with lights, the charging socket and cigarette lighter.
The instrument cluster per se minus the lights gets power thru Fuses 15, 23, 27, 31, 45 & 46
The onboard computer is powered thru 23, 27, 31 & 45
The fuel level sensors (there are two, one on the left side tank and another on the right side or pump side tank) are connected to the cluster/panel in the same connector that goes to the fuel pump. There are 4 wires to the pump.
2 are bigger and are the positive and the ground wire to the pump. The other 2 which are smaller are the fuel level sensor wires which goes to pins 3 and 1 of the instrument cluster. Provided there is continuity from end to end of both wires(when tested unpowered, with connectors end to end detached), then the fault lies in the sensor. Now which one,
left side or right side/pump side is the problem. They are not really costly. I would suggest replacing the right one first. Then if  the gauge is still not working, then replace the left sensor.
You do not have to guess if you can have the car diagnosed with a BMW DIS or GT1 tester(scanners).
I am basing my recommendations to replace the fuel sensors
on the assumption that your cluster's gauges are working.
Sometimes but not often, it is the cluster that is bad.
I think I have already told you more than you asked for.
Cheers!
Tino