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temp and fuel gauge problem


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Pull the Yellow/White stripe wire off the sender (located on the front of the thermostat housing) and ground it with the key ON. Gauge should climb to full HOT. Wire and gauge are working normally.

 

If no reading the wire or a connection between you and the gauge is likely.

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  • 2 weeks later...

I have this exact issue! Which fuse is it?!!! I have no oil light on start up either and both my temp and fuel gauges dont work but I have a wiring mess going at the fuse block. :) I didnt get far with the wiring diagram as all the wires have been changed by the previous owner. 

 

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The same fuse works the fuel/temp gauges and the oil light... but also supplies the CHARGE light and the BRAKE light. Turn key to ON and pull the e brake handle out... does the brake light com on? Before cranking the motor is the charge light on? It should be. Find the fuse box and look for the White/Blue stripe wire going to a 10 amp fuse. Change the fuse, don't even look at it, just change it. Looking is unreliable, sometimes they are no good and you can't tell.

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Thank you! I appreciate it. The brake light does not come one. Here is my list of wiring woes:

-no brake light (didnt even know there was one)

-blower doesnt turn on (havent even looked yet)

-windsheild wipers dont turn on (havent looked either)

-no oil light on start up

-no fuel or temp guages.

 

I bought the truck 5 days ago and am just going through everything (fuel pump, distributor, hoses, fluids, mounts etc and decided for electrical to be this next weeks chore. I did the gm 1 wire alternator conversion today, and worked like a champ. Thank you for your help, I'm sure I'll run into you again on here as I try to find my electrical issues here in the next few days.... 

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I often forget the fuse box on the 521 is under the hood. Disconnect the battery and carefully disconnect the fuse box and remove the fuses. Probably won't hurt to draw a picture of it and the wire color codes or lots of digital pictures.

 

Clean the fuse box and soak overnight is a bath of vinegar. This will remove all the corrosion from the copper and the fuses with make better contact. Oh yes replace the fuses with new ones.

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  • 4 months later...

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I often forget the fuse box on the 521 is under the hood. Disconnect the battery and carefully disconnect the fuse box and remove the fuses. Probably won't hurt to draw a picture of it and the wire color codes or lots of digital pictures.

 

Clean the fuse box and soak overnight is a bath of vinegar. This will remove all the corrosion from the copper and the fuses with make better contact. Oh yes replace the fuses with new ones.

 

My fuel and temp gauges, Brake, Oil-P, and CHG light do not work.  They were working fine, but all of a sudden they died while driving.  Every time I replace the fuse it blows.  Any ideas on what it could be?  The connection to the battery is perfect, so is the alternator connections.  Fuse box is clean, Emergency lights work perfectly.  My turn signals, and the lights and gauges mentioned above are the functions that do not work.  Any ideas?

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Yes look here... http://community.ratsun.net/topic/59029-turn-signals-brake-oil-p-chg-fuel-gauge-and-temp-gauge-just-went-out/

 

 

All those items are not working because they are on the fuse that is blown. Find the cause of the blown fuse and you will have fixed all the problems. Something on that fused circuit is drawing too much power and to save the wiring the fuse blows. This is it's job.

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My 610 has the same issue, except for the fuel and temp gauge are constantly showing low.. once in a while, it will climb up and register where it's supposed to, but for the most part, they're useless to me. Been using to odometer to monitor my fuel level for a year now :( As for my temp, luckily I have an oil temp gauge, so I'm alright there.

 

Still having my original issue. Swapped out gauges for new ones, same issue. COMPLETELY disassembled harness to check all connections and grounds; all fine. Also, my charge light comes on dimly when I turn on the blower motor, and the light intensifies with each step up from 1-3. It never comes on fully, but it gets brighter step by step(Has always done this as well). This all started with me wanting to get a correct reading on my fuel/temp gauge, and wanting my rear window defroster to work. I've cleaned my fuse box, replaced all fuses, yadda yadda yadda. Alternator has been replaced with 3 different, higher amperage output units with the same result. Anybody have any ideas? I'm just about ready to yard the entire wiring harness out and replace with a different one.

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It wavers at times.. interesting development.. I found that the blower motor was spliced into the Gauges fuse line, rather than going to the Air Conditioning fuse. Looked like it was done factory, but didn't follow the factory schematic I have. Cut the wire and the light went out, as well as the blower motor. Scotch locked it into the correct fuse(A C), and the blower motor came back on.. so did the dim charging light.. ugh.. this tells me that the issue is further upstream.

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Ya know I'm not the best person to diagnose dash/interior related issues.

Have you considered your dimmer switch or hazard switch ?

The earlier z's (depending on year) ... have a hazard switch in which everything is routed through ...

although I'm not sure if this is even close to area of the original intent on the fuel gauge etc..

 

 

Although I'm certainly far away from being a pro tech.

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The turn signal flasher is connected to the signal lamps through the 4 way. When you switch the 4 ways on, the signal flasher is disconnect. When you shut the 4 ways off the signal flasher is re connected. I haven't found any Datsun wired differently.

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opps $^%$ ! lol ... I meant the earlier Z's have a different type/style of hazard switch that is more prone to getting gummed up/mal-functioning.... causing weird shat. It may not be the case with all just something I've noticed :)

 

Thanks Mike ! this is the area where I'm less proficient !!!!

 

 

I'm bowing out ....

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You said you changed the gauges, right? Did you also change the gauge voltage regulator??? It will look like this little rectangle metal can thing and plug into the back of the gauges...

 

 

 

This is a '68 gauge so not exactly the same but may look the same.

68510vreg.jpg

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This will help you 521 guys.

Pinout.jpg

Get a 12 volt battery.  Connect battery negative to the ground pin, 10:00 o'clock.

Applying power to high beam, right turn, dash lights, and left turn should make those lights come on.

Apply power to ignition power in, AND also ground,  grounding IGN, and OIl light terminals should make those two lights come on.

With power applied to Ign power in, and the battery negative still connected to ground, grounding fuel sender, or temp sender will make those gauges go to full, or hot.

 

If you use a test light to connect the fuel sender pin. or the temp sender pin to ground, the test light will flash, and the gauges will read somewhere in the middle.

 

 

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This afternoon I left no stone unturned. Checked every connector, every fuse, every ground. All fine. Swapped out gauges, voltage regulators and grounded sensors. With the key in the "Run" position, the OIL and CHARGE lights come on, but slightly surge or pulsate(always doing it, in an inconsistent pattern). The Fuel and Temp gauges waver with every pulsation. This made me think it was a ground, but I checked every ground, cleaned all connections, and even created new grounds and doubled them up. I am having a difficult time with this, as it was what I excelled at most in school. I'm about at my whit's end; been battling this off and on for years.. to say it's frustrating wouldn't do justice to the irritation this is causing me.

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Did you check the connections between the engine room harness, and the cab harness, behind, or alongside the glove box?

 

The gauge voltage regulator is basically an overloaded circuit breaker.  It is on, when the key is first turned on, and gets warm, and then it opens up, cools down.  Then switches back on.  The gauges are designed to react slower than the gauge voltage regulator, so most people do not notice the gauges fluctuating a little.  If you look close, you will notice it, especially when you first start the truck.  The fuel gauge is really noticeable, because the temp gauge is not going to move on a cold engine.  If your gas tank is close to empty, when you first start the truck, and the fuel gauges moves above empty a little, and then reads empty, you probably have a little gas left.  if your tank is really empty, the fuel gauge does not "flare" higher than empty, for a brief period of time.  If you do not see this rise, get some gas.  First thing you do.

 

The same power that supplies the OIL and IGN light also supplied power to the gauges.  Those light will flicker too, as the gauge voltage regulator turn on and off.

 

The gauges, and the whole electrical system, in a 521, by today's standards are not all that sophisticated.  I think there is a possibility you may be looking too hard for a fault, that is not a fault, but the way they designed electrical systems in 1970.

 

A 40 ohm resistor between the yellow and white temp sender wire, and ground should make the temp gauge read close to the line in the middle of the grey area on the temp gauge..  A 35 ohm resistor connected to the two wires on the fuel gauge sender, with the wires removed from the sender should make the fuel gauge read about a half tank.

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Did you check the connections between the engine room harness, and the cab harness, behind, or alongside the glove box?

 

Yes. Removed them all and cleaned them. At all 3 different points in the harness(Under the relay back under the hood, at the firewall, and at the driver's side of the passenger compartment.

 

The gauge voltage regulator is basically an overloaded circuit breaker.  It is on, when the key is first turned on, and gets warm, and then it opens up, cools down.  Then switches back on.  The gauges are designed to react slower than the gauge voltage regulator, so most people do not notice the gauges fluctuating a little.  If you look close, you will notice it, especially when you first start the truck.  The fuel gauge is really noticeable, because the temp gauge is not going to move on a cold engine.  If your gas tank is close to empty, when you first start the truck, and the fuel gauges moves above empty a little, and then reads empty, you probably have a little gas left.  if your tank is really empty, the fuel gauge does not "flare" higher than empty, for a brief period of time.  If you do not see this rise, get some gas.  First thing you do.

 

I've replaced this with 3 other units. 2 of them look to be solid state, the first was more of a points style. They all act exactly the same. I have also replaced the gauges themselves with other known good units, to no effect.

 

The same power that supplies the OIL and IGN light also supplied power to the gauges.  Those light will flicker too, as the gauge voltage regulator turn on and off.

 

The gauges, and the whole electrical system, in a 521, by today's standards are not all that sophisticated.  I think there is a possibility you may be looking too hard for a fault, that is not a fault, but the way they designed electrical systems in 1970.

 

I thought this may be the case, until I checked out my 73 610 coupe. Should have the exact same system as my wagon. The gauges read rock steady, and do not fluctuate at all(well, as is noticeable by my eyes when sitting back in the driver's seat. When grounded, the fuel gauge maxes out, but will still fluctuate about 1/8th of a tank's worth, back and forth.

 

A 40 ohm resistor between the yellow and white temp sender wire, and ground should make the temp gauge read close to the line in the middle of the grey area on the temp gauge..  A 35 ohm resistor connected to the two wires on the fuel gauge sender, with the wires removed from the sender should make the fuel gauge read about a half tank.

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