The missus has a 2000 VW POLO 1.0lt with a fuel gauge that sometimes shows the tank to be empty when its at least half full. It seems to be happening more often. Has anybody else seen this problem on the POLO?
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My first port of call woyuld be the tank sender unit. First disconect the battery (or else BANG). In the past the sender unit was accessable through a plate in the floor. Unscrew the unit after detaching the wires, and investigate. Many years ago mine was playing up, and all I did was clean it, and slightly bend the contact arm that touches the unit (which is in effect one resistor) so it made better contact. Worked fine after.
If not replace the unit.
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If the instrument unit is made by VDO, the most likely cause is a poor connection on the flexible printed circuit behind the gauges. Their method of crimping component wire ends to the unplated track is doomed to failure as a gas tight joint is not possible with their detailing. On several of these units (not necessarily VW) I have had to solder a jumper wire between the incoming connector from the vehicle wiring loom to the sub-panel containing the gauge damping and WL switching circuit in order to obtain consisitent results.
Once this is done, the gauges are quite accurate as the tank units are thick-film resistors laser trimmed to match the profile of the tank. In my experience, these later tank units give no trouble.
The best way of identifying the gauge fault is to measure the voltage drop across the various sections of track with a DVM on a low mV range when the tank is full and the ignition on. The current is at its highest under these conditions.
Intermittent faults are difficult, but in this case the design was so poor that I simply linked out all of the track to the gauge with complete sucess.
659.
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good post 659FBE my good slap on dash will be of no use then :( but usually works for plenty of cars :)
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