Pacific coast Datsun Posted October 5, 2009 Report Share Posted October 5, 2009 Ok long story short is..the gas gauge on my 74 620 has never worked correctly and recently i've noticed that now the gauge does'nt even move when the truck is running. In the past the needle will move & register that there is gas in the tank but it's never been acurate. Ive read here that guys have fixed thier gas gauge issues by messing with an electrical part behind the cluster....also could the issue also lie in the float inside the tank?? I need some pointers on how to fix this major issue..running out of gas sucks big time...;) Quote Link to comment
1972.5 dat Posted October 5, 2009 Report Share Posted October 5, 2009 need new send in tank sound like start 2 me Quote Link to comment
datzenmike Posted October 5, 2009 Report Share Posted October 5, 2009 If the voltage regulator behind the cluster was bad the fuel AND temp gauge would be bad. Quote Link to comment
Pacific coast Datsun Posted October 5, 2009 Author Report Share Posted October 5, 2009 If the voltage regulator behind the cluster was bad the fuel AND temp gauge would be bad. Ok forgot to mention..the temp gauge is also "touch & go". It'll give a reading but i dont think it's accurate. Quote Link to comment
datzenmike Posted October 5, 2009 Report Share Posted October 5, 2009 Ground the temp wire at the sender, temp gauge should read full scale. Gas sender would do the same if grounded. The 521 and 620 have a small plug in volt regulator on the back of the instrument pannel. The regulator keeps the voltage for the gauges around 8 volts so fluctuations in the battery voltage (12 when off and 14.4 when running, or in between when headlights are on) dont cause the gauges to read high and low all the time. Quote Link to comment
yello620 Posted October 5, 2009 Report Share Posted October 5, 2009 Mike, do you have a picture of this voltage ragulaltor on the back of the cluster? Quote Link to comment
datzenmike Posted October 6, 2009 Report Share Posted October 6, 2009 Had a picture but I think it's for the 521. The regulator in inside the gauge cluster so take it out and dismantle. The regulator is a bi-metallic coil that heats up with current flow and opens the circuit. As it cools it reconnects and begins to heat up again. The opening and closing produced a pulsating output of about 8 volts. The contacts may be loose/corroded/dirty. I went out and looked at my spare dash and can't see a thing from the outside. Quote Link to comment
Pacific coast Datsun Posted October 6, 2009 Author Report Share Posted October 6, 2009 Thanks Mike..ill look into finding that regulator. Quote Link to comment
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