ColtonMelson Posted January 26, 2013 Report Share Posted January 26, 2013 my fuel and temp gauges do not work. I need some help here on how to truble shoot this and find out what is wrong. Bad ground, were is the ground for them?, bad gauges, or bad sending unit? Were is the temp sending unit and how do i test it?? Quote Link to comment
ggzilla Posted January 27, 2013 Report Share Posted January 27, 2013 Do the idiot lights and t/s lights in the dash work? If so, and only the temp and fuel are not working, it is likely the Instrument Panel Voltage Regulator that is bad. It controls both the fuel and temp gauges. Quote Link to comment
datzenmike Posted January 27, 2013 Report Share Posted January 27, 2013 Turn ignition to ON... Pull the hand brake ON does the BRAKE light in the dash light??? If it does then there is power to the voltage regulator that feeds only the temp and gas gauges. If the tank is empty and the motor cold these will not read. To check the temp gauge, find the temp sender just below? the thermostat where the top rad hose clamps to the intake. It will have a Yellow wire with Black stripe. Ground this wire on the intake and the gauge should read full HOT. If not then the gas gauge being out also would indicate that the voltage regulator is faulty. These are 620 gauges and NOT 720 but they are ... similar. Take the dash gauge bezel screws out and disconnect the speedometer cable (you may be able to pull some extra cable for enough slack) and pull the gauge cluster towards you to access the temp and gas gauges. The volt regulator is likely in one of them and may look like the one in the picture. There may simply be a bad contact on one of the plugs on the back of the cluster, so unplug and plug them in several times to clean the contacts. Quote Link to comment
ColtonMelson Posted January 27, 2013 Author Report Share Posted January 27, 2013 Thx guys.. So my brake light does not come on when i pull the e brake. BUT when my brake fluid is low, the light comes on and will not go off until i fill it back up with brake fluid and pump the brakes a couple times. I have to add brake fluid once a week cuz i have a leak in my rear passenger side wheel cylinder. I have not tried to ground the temp wire to the manifold yet, but i will tomorrow when the sun comes up. The fuel and temp gauge have not worked sense i got the truck. I had put a new thermostat in it, got it really hot, and checked the temp. Im not comfortable with this anymore. i need it fixed :yawn: Quote Link to comment
ColtonMelson Posted January 28, 2013 Author Report Share Posted January 28, 2013 ok so i grounded the temp sensor wire and got nothing. Im guessing it is the voltage regulator. Now to replace this do i just buy a new gauge? or do i replace the voltage reg thats on the gauge? Hope to get some pics up tomorrow. just added a tool box to the bed and adjusted the torsion bars to pick up the front end and level the truck. Also get some new toyos tires put on. Its lookin pretty sweet B) Anyone have a rear bumper they could sell?? chrome if possible. ONE MORE THING i looked for the number to find out my rear-end gear ratio. the plate under the hood on the passenger wheel well. the code just above the W on the bottom was HE35. any one know what that translates to for the ratio? and what are my option on that? Quote Link to comment
datzenmike Posted January 28, 2013 Report Share Posted January 28, 2013 3.545 I think. Since both gauges are out it's probable that there is one voltage regulator for both. Tell the truth I have never found it or knowingly seen it. I have a gauge cluster at home and have looked at it but didn't see anything that looked like a regulator. Quote Link to comment
ColtonMelson Posted January 28, 2013 Author Report Share Posted January 28, 2013 ok so i pulled the gauge cluster out and found the voltage regulator on the fuel gauge side. I found a little burnt spot on the white thing right under the points. i also see the is a very very small crack there. SO how can i fix it? any ideas? Quote Link to comment
datzenmike Posted January 28, 2013 Report Share Posted January 28, 2013 Well if you can find a round gauge 720 in a wrecking yard near you (you are in the PNW) just replace it. Just for fun I took the tiny screws off the gauge face and removed it. Does not look like anything is removable. You can more clearly see the contact points that open and shut to maintain an 8 volt supply to both gauges. If the battery voltage was used it would range from about 12 to as high as 14.8 and the gauges would read differently at idle with heater and wipers on. Quote Link to comment
ColtonMelson Posted January 29, 2013 Author Report Share Posted January 29, 2013 I was testing the voltage on the 4 wires running to the volt reg and the fuel gauge and at first i had only gotten voltage out of the red hot wire, But then all of a sudden the whole system started working! gas gauge moved up and temp gauge move too (not pegged) and my break light came on!. so i turn off the truck and started it again. Everything worked. I was really happy and began putting everything back together........... I started the truck.... the gas gauge and temp did not work again..... very frustrating.. But i did see that my voltage regulator IS replaceable. A couple screws and unclip the connector and its out. But you cant order them. So yes in stuck with 3 options. See if i can get it to work again (not likely) change the gauge cluster (preferably with a tach on it) or swap in a new volt reg.... This lil datsun is a very fun and easy truck to work on. great for a guy like me to tear into and learn something... Thanks for all the help Quote Link to comment
ColtonMelson Posted February 1, 2013 Author Report Share Posted February 1, 2013 Just wanted to say i scored a gauge cluster today for 30$ out of a junk yard. Hooked it up and I finally have a fuel and temp gauge (and about 70,000miles less) Im going back tomorrow to get the rear bumper off that 720 :thumbup: After that, im goin for some bucket seats With a Head Rest! Quote Link to comment
DuckSatan Posted March 22 Report Share Posted March 22 On 1/28/2013 at 4:53 PM, datzenmike said: Well if you can find a round gauge 720 in a wrecking yard near you (you are in the PNW) just replace it. Just for fun I took the tiny screws off the gauge face and removed it. Does not look like anything is removable. http://i138.photobucket.com/albums/q251/datzenmike/Nissan%20Electrical/720fueltempgaugevoltregulator001Large.jpg You can more clearly see the contact points that open and shut to maintain an 8 volt supply to both gauges. If the battery voltage was used it would range from about 12 to as high as 14.8 and the gauges would read differently at idle with heater and wipers on. http://i138.photobucket.com/albums/q251/datzenmike/Nissan%20Electrical/720fueltempgaugevoltregulator002Large.jpg What is this black wire. Also so i have re wired the entire truck. is it 12v going into the fuel guage, then stepped down to 8v for the fuel guage/sender and temp guage/sender? ive wired the oil/ebrake/alt/back lights seperatly on their own fuse. fuel guage and temp guage need to be wired now. Quote Link to comment
Joecar Posted March 22 Report Share Posted March 22 Something similar is happening but when the truck has a full tank it doesn’t go all the way up Quote Link to comment
datzenmike Posted March 22 Report Share Posted March 22 Most likely the float on the sender sticks. Run the tank near empty, drop the tank, unscrew the sender and remove from the tank. See if the float has full swing movement. Quote Link to comment
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