BMW Fuel Sender Repair

BMW fuel senderThe fuel gauge on the Bavaria stopped working.

I was hoping that it was only a bad ground connection on the instrument cluster. On my first repair attempt, I hit the top of the dash above the instrument cluster to jostle the connections and take out some frustration. When only the latter worked, I looked at my BMW repair CD.

To test the fuel gauge, the repair manual said to connect the brown-yellow wire on the fuel level sender to ground and to switch on the ignition momentarily. The gauge deflected to full, so I knew the gauge and grounds were OK. But that meant the sender was broke.

RealOEM.com lists the price of new sender at $261.40 (USD), so that was a good reason to try to fix it.

BMW Fuel Sender Sensor wire routing

After I moved all the crap in the trunk to one side, I lifted the carpet and unscrewed the floor panel covering the gas tank.

The gas tank was full. When I tried pulling the sender out of the tank, (it’s a bayonet mount) gas poured out into the trunk. I decided to take a drive down Highway 1 a little south of Point Lobos to lower the fuel level.

The fuel sender is basically a variable resistor. The float moves up and down a guide rod and is also connected to a wire of known resistance. The change in resistance (by the position of the float) is translated by the fuel gauge as the range from full to empty.

BMW fuel sender repair

One end of the sensor wire had broken off its terminal connection so the wire was now too short to connect to the terminal. I used a piece of 22 gauge solid copper wire (looped and soldered to the connector) to extend the connection so the sensor wire would reach its terminal. Since the sensor wire is a continuous run from one terminal to the other, I had to figure out the routing around the bottom of the sender. It seemed to just wrap around – at least that’s how I did it.

The repair manual says the resistance between the G terminal and minus should measure 3.2 & 73.7 ohms at the extreme positions of the float. I measured 3.4 and 84.7 ohms so at least my repair sorta worked.

Macbook and Powerbook Repair

Apple Inc (AAPL), stock hit an all time high today (it closed at 98.84), while my two Macs hit lows.

Powerbook G4 DC-In Board

The Ethernet port on my Macbook (13″ Late 2006) failed. It seems that the connection to the logic board is loose. The nearest Apple Store is 72 miles away, and since I figured it’ll need a new logic board, I sent it off Apple Mail-In Repair in Tennessee. It’s still under warranty. They received it today and the repair status says, “On hold – Part on order (26-Apr-2007).” I guess that means they’ll fix it “real soon now.”

My other Mac notebook, a 4-year-old Powerbook G4 12″ (rev A) decided that it was going to have an intermittent connection with the DC power connector. I purchased AppleCare for this computer when I bought it, but that ran out about a year ago. So I had to fix it myself.

Powerbook G4 Internal PartsI highly recommend ifixit.com because they give step by step disassembly instructions with photos. It was a pain to take apart, in spite of ifixit.com’s excellent instructions, because the part I needed to fix required that everything else taken apart (except the display) first.
When I finally got everything apart, I could see the broken solder joint (circled in red) that was causing my intermittent power connection.

Powerbook G4 DC-In Board

I guess it did “Test OK” when it was manufactured, but not now. A few seconds with a hot soldering iron and the connection was fine. Then it took me another hour to put it back together. As I said, a pain.