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Fuel Sensor Repair

Magna reserve tank low fuel sender trouble shooting and repair.


  1. When the key is turned on, the low fuel light (2nd from left) on the cluster should light - verifying the bulb is working.
  2. With the key on, remove the two wires from the sending unit and short them together. If the light comes on, the circuit is working correctly.
  3. Drain the reserve tank and remove the sender. Reconnect the wires and turn the key on for at least 1 minute. If the light comes on everything is working properly.
  4. If the light fails to come on the sender is broken and must be repaired

Sender Repair: (Tools Needed)

(Parts Needed)

(Process) With the sender removed from the reserve tank perform the following:

  1. Clamp the sender in the vise and unsolder the bracket from the can.


  1. The can may pull off the plastic insulator, if not, locate the 3 punch marks at one end of the can near the plastic. Using a small drill (3/32), drill out the punch marks to free up the plastic.
  2. Pull the plastic out of the can. The thermistor will probably be missing, only the two lead wires will remain.
  3. Clip the old lead at the plastic to about 1/2 inch and bend a small U on the end of it.
  4. Unsolder the lead at the end of the can opposite the plastic and remove the old lead wire. Drill out the center of the can with the 3/32 drill bit.


  1. Clean up the can, especially the screened holes where the gas goes in and out. If the screen is coming off the inside of the can then you can remove it. (It doesn't seem to serve any purpose)
  2. Take the new thermister and bend one lead around 180 deg so it is opposite the other. (Doesn't matter which lead you bend)
  3. Cut off the un-bent lead to about 1/2 inch and bend a small "U" on the end of it.


  1. Connect the "U" thermister lead to the old "U" lead on the plastic by interlocking and pinching the U's together.
  2. Solder the connected leads together. (Careful not to overheat and melt the solder on the thermister)


  1. Insert the thermister and plastic into the can - with the other lead coming out the hole in the end of the can.
    1. IMPORTANT: The lead going to the plastic cap cannot touch the inside of the can.

  2. Solder the can to the bracket. Repunching of the can to the plastic is not required.
  3. Solder the end of the can to the thermister lead and cut off any excess lead.


  1. Testing: with the unit out of the tank, connect the leads and turn on the key. After about a minute the alarm light should start to glow red and get brighter.
  2. Re-install sender in tank with a new O-ring size of 0.75 ID x 0.95 OD thickness 0.100. (L14 in the Harbor Freight O-ring set)

Sounds complicated, but the hardest part is drilling out the punches.

Thanks to Jason Starwalt for the donation of his spare sender for use in the photos. Thanks to Ron Warren for permission to post this writeup.