fuel gauge problems

[Zulfiqar]

Ive had this problem forever, that when I fill the tank to full the gauge shows, 3/4 only and slightly higher in the nightime.

So I took off the gauge cluster and replaced the voltage regulator from the back of it, my cousin repairs wireless radios and VSAT modules. So I nicked one from him. The original was some french part, the new one is japanese NEC, Its some 10V type, just unscrew it from the back and take to a circuit component shop I bet they'll have plenty of them.

Voila The fuel guage works spot on, even the temp one is very sensitive to changes now. Rather than - (Relax the temps are under control)

[somolovitch3]

Could we get a more specific NEC part number?

[Zulfiqar]

OK, I'll get one from him and post the number

[wikdslo]

This seems to be the problem that I am having on my cluster. 3/4 when full to the brim. No idea how much is actually in there at any other given time.

Anyone have more info on this issue?

[neimis]

I don't know what car you have, but there is a known problem with the voltage regulator. Mine was defective - when replaced, my fuel gauge and temperature gauge problems were solved ('92 Passat TD).

The solder joints on the board are also a known problem. Here is something I borrowed from someone (? sorry, don't know who it was) on the Vortex:

RE:  bad solder joint affecting the fuel/temp gauge
Remove the circuit board from the cluster. The solder joints that hold the socket for the 3-pin chip are probably defective. Resolder the holder and the chip, this may solve the fuel and temperature gauge problems. Sometimes the problem is not the voltage stabilizer itself but rather the 6 pins soldered to the board that is basically a socket for the voltage stabilizer.
I resoldered the six pins and reassembled it... better but some of the stuff was still acting funny. I removed it again and took a good hard look at all the solder joints on the board. I found over 7 bad/cracked/dry joints where the main socket connects to the board (where wire harness plugs in). I resoldered all of them, put it back together and my cluster works like new!
Some of the problems I was having with the cluster that led me to resoldering these were:                                                                                                    
           -Gas gauge intermittent                                                                                                  
           -Temp warning light continuously flashing for no reason
           -Alt/battery light would not light up when I turned the key forward                  
            (exciter circuit)
           -RPM gauge intermittent
           -Coolant temperature gauge would read false (much too high)

Once I resoldered the loose joints on the board all problems were solved!

Hope this helps, Neil Miskey