Gas gauge/sender wiring question.

[spoolinitup33]

I asked this over on the realm and didn't get too many answers:

 

There is NO stock wiring in my car whatsoever. I have the stock sending unit in my gas tank and I have the stock gauge cluster in the dash. The only two things I want to use on the gauge cluster is the fuel level and the speedometer. I can get the speedometer working, but I need some help on the fuel level gauge. I don't know how to wire it or anything, and I don't have the plug that goes to the gauge cluster. In the picture below, I have red arrows drawn to where I think power should go. The blue arrow is where I'm guessing the wire goes from the sending unit goes, am I right?

 

[DanielC]

I am assuming the picture is the back of the Combo meter for your 1972 510

I figured out the connections on a 1971 521, and I think thet are similar.

 

Do you have the plug that goes onto the ten pins in the upper right of your

picture? Getting that plug would be the best way to hook up the meter.

 

The ten pins in no order have these functions.

 

Positive battery voltage, from the key

Negative battery connection

Right turn indicator

Left turn indicator

High beam indicator

Low oil pressure indicator

Alternator indicator (may be labeled "IGN")

Fuel gauge sender

Temp gauge sender

Gauge lights

 

It would take me a little work with a magnifying glass, stating at my 521 diagram to tell you what each pin does, on a 521, and your 510 probably is different, so right now, I am not going to bother. Later tonight, I just might dive into it.

 

Bare minimum, for your fuel gauge to work, you need battery voltage applied to the combo meter, probably from the key, you need to supply a ground for the combo meter, you have to hook a wire from the fuel tank sender, and you have to make sure the fuel tank sender has a good ground.

Since you are rewiring anyway, I would run a ground wire alongside the fuel sender wire, connect that to the combo meter ground wire, and make sure both have a good ground.

[spoolinitup33]

I am assuming the picture is the back of the Combo meter for your 1972 510

I figured out the connections on a 1971 521, and I think thet are similar.

 

Do you have the plug that goes onto the ten pins in the upper right of your

picture? Getting that plug would be the best way to hook up the meter.

 

The ten pins in no order have these functions.

 

Positive battery voltage, from the key

Negative battery connection

Right turn indicator

Left turn indicator

High beam indicator

Low oil pressure indicator

Alternator indicator (may be labeled "IGN")

Fuel gauge sender

Temp gauge sender

Gauge lights

 

It would take me a little work with a magnifying glass, stating at my 521 diagram to tell you what each pin does, on a 521, and your 510 probably is different, so right now, I am not going to bother. Later tonight, I just might dive into it.

 

Bare minimum, for your fuel gauge to work, you need battery voltage applied to the combo meter, probably from the key, you need to supply a ground for the combo meter, you have to hook a wire from the fuel tank sender, and you have to make sure the fuel tank sender has a good ground.

Since you are rewiring anyway, I would run a ground wire alongside the fuel sender wire, connect that to the combo meter ground wire, and make sure both have a good ground.

 

No, I don't have the plug that goes to those 10 pins. I can figure out a way to connect them though, that shouldn't be a problem. I'm confused about all the grounds you're talking about. There are only two connections that go to the gas gauge. One of them is going to have to be power, and if I hook the other to ground, where is the wire from the sender going to connect? That blue arrow has to be where the wire from the sending unit goes, and then first red arrow to the left of the blue arrow would be where the power goes, right? Or would that be the ground? But then where will the power wire go?!

Edited November 23, 2009 by spoolinitup33

[DanielC]

Here is an update. I got curious. Again, this is for a 521. Your 510 may be different, it could be the same, there are no guarantees.

If you look in the center of the pins, there is a hole, with a keyway. Your keyway looks damaged, it might not be.

 

On a 521 combo meter, the pin closest to the keyway is pin 1. The pins are numbered clockwise from there. Pins 6, and 7 are missing.

Pin 1 power comes in from right turn signal, light comes on.

Pin 2 power comes in from light switch, combo meter lights come on.

Pin 3 power comes in from left turn signal, light comes on.

Pin 4 this is the sender connection for the fuel gauge.

pin 5 with the combo meter receiving power, grounding this pin lights the oil light.

pin 8 this is the connection for power into the combo meter from the key.

pin 9 with the combo meter receiving power, grounding this pin lights the ign light.

pin 10 power comes in from the high beam headlights, light comes on.

pin 11 ground

pin 12 this is the sender connection for the engine coolant temperature.

[datzenmike]

Don't forget also that the gas and temp are not connected to 12 volts, but a voltage regulator that supplies about 8 volt. This prevents the gauges from jumping up and down from voltage fluctuations form idling with or without the headlights/heater/wiper going.

[DanielC]

First of all you cannot really hook the stock fuel gauge up directly to battery power. There is a voltage regulator used in the stock system to make both the gas level gauge, and the temperature gauge more accurate. I do not see the regulator in your picture, but it might be farther to the right on the circuit board, and not in your picture.

 

In order for the fuel gauge to work, the combo meter needs to get power, and of course, it needs a ground. Once that happens, the fuel gauge needs to be connected to the sender. The sender is just a variable resistor, low resistance for a full tank, higher resistance for an empty tank. My 521 service manual says with the wires disconnected from the sender at the tank, and connected to a 35 ohm resistor, the fuel gauge should read 1/2 full.

 

I am not sure about where the connections all go on your combo meter. I think the red arrow, farthest right in the picture, pointing to a screw hole could just be power for the combo meter lights. Or it could also be a ground. I do not know. It looks to me like that copper trace goes to the three lights. It is really hard to tell, without a closer look.

[DanielC]

Could you take a picture of the back of the whole combo meter?

 

Try to identify what each pin on the plug goes to. I already posted what each of the ten pin functions are for my 521. I believe the 510 would be similar, if not the same.

 

One side of the right turn, left turn, and high beam indicators will have only one connection at the light, and at the ten pin plug. Find those pins.

One side of the oil light, and the ign light will also have only one connection at the light. find those pins.

five pins to go.

If you remove all the lights, you should be able to connect one lead of an ohmmeter to the metal side of the combo meter, and touch all the other pins, and the one pin that shows the lowest ohm reading is probably the ground. Look for a resistance of less than one ohm. Somewhere on this copper trace, there may be a rivet connecting this trace to the metal body of the combo meter. on your picture, this looks to me to be the pin in the 7:00 o' clock position

four pins to go.

Go back to the ign, or oil light. Look at the copper trace on the other side of the light, and you should find a few extra connections. You may find a copper trace connecting these two lights together. This is the connection for the battery to power the combo meter through the key.

three pins to go

Look for a copper trace that goes to four or more lights. If you can identify the "dash" lights, this is the trace you are looking for. Follow it back to the 10 pin connector. On mt 521 combo meter, this trace is on the outside of the circuit board. The other side of the dash lights go to a rivet to ground them.

Two pins left.

One is the fuel sender connection. The other is the temp sender connection.

 

Once you have found all the connections, connect the ground pin to the negative side of a 12 volt battery.

Now touch a wire from the positive side of a 12 volt battery to the right turn, the left turn, and the high beam indicator. The three lights should light up as you make each connection. Check the four or more dash lights.

Now, connect the battery positice to the power in pin you found. With the combo meter still grounded, and power applied, nothing should happen.

Take a third wire, connect it to the negative battery terminal, and touch the pin for the oil light. It should come on. Touch the pin for the ign light. It should come on.

Grounding one of the two pins left should make the temp gauge go to full hot

Grounding the last of the pins left should make the fuel gauge go to full.

[spoolinitup33]

I knew about the voltage regulator, it's on the gauges. I had the gauges removed in those pictures. I'll get it figured out, I just need my ohm meter. I just want the gas gauge to work!!

[MikeRL411]

When you get the pins all sorted out, go to Kragen or whatever parts store is nearby and buy a pack of female "bullet" connectors. Solder or crimp your wires to the bullet ends and plug them on to the proper pins on your instrument panel connector. You need to send the regulated 8 volts from the panel to the "top" of the float, return the "slider" voltage to the panel and provide a proper ground. Use 3 pins for best results or else insure that your instrument panel board is very well grounded [it probably isn"t].

[spoolinitup33]

When you get the pins all sorted out, go to Kragen or whatever parts store is nearby and buy a pack of female "bullet" connectors. Solder or crimp your wires to the bullet ends and plug them on to the proper pins on your instrument panel connector. You need to send the regulated 8 volts from the panel to the "top" of the float, return the "slider" voltage to the panel and provide a proper ground. Use 3 pins for best results or else insure that your instrument panel board is very well grounded [it probably isn"t].

 

?? What is a slider and what is a float?

[MikeRL411]

?? What is a slider and what is a float?

The gas gauge is a lever arm connected to a float inside the gas tank. Do I have to tell you what a float is? The arm rotates a potentiometer [look it up I don't have that much time] usually a wire wound resistor such that when the tank is empty, the "arm" of the potentiometer is at the bottom of its rotation [full resistance] and the wire connected to the arm [slider] reads full ohmage. If you remember to add gas, the internal float rises, and the "slider" or wiper arm moves towards the top of the potentiometer, decreasing the resistance. To put it simply, more current flows through the potentiometer, and therefore the meter which now shows that there is indeed some gasoline in the tank.

[spoolinitup33]

Ok nevermind I knew what you were talking about I just wasn't thinking. This just doesn't make sense. There are THREE places on the fuel and temp. gauges that wires go. I took some pictures so you can see for yourself.

 

Edit: I just realized, I don't think I have a voltage regulator, unless it's somehow in these gauges.

 

The gauges

 

Two of the places where wires could go

 

The same two on the left, the other connection on the right

 

 

Edited November 24, 2009 by spoolinitup33

[DanielC]

I do not think you can make the gauges work without the voltage regulator. they are designed to work together.

[spoolinitup33]

Well shit, I was thinking the whole time that there was something in those gauges that regulated the voltage from the way people were telling me, but it's actually like a little metal box isn't it? I guess I can get one. But still, there's still only going to be two posts to hook wires to that go to that fuel gauge.

[MikeRL411]

The gas gauge is a lever arm connected to a float inside the gas tank. Do I have to tell you what a float is? The arm rotates a potentiometer [look it up I don't have that much time] usually a wire wound resistor such that when the tank is empty, the "arm" of the potentiometer is at the bottom of its rotation [full resistance] and the wire connected to the arm [slider] reads full ohmage. If you remember to add gas, the internal float rises, and the "slider" or wiper arm moves towards the top of the potentiometer, decreasing the resistance. To put it simply, more current flows through the potentiometer, and therefore the meter which now shows that there is indeed some gasoline in the tank.

 

I misled you a bit. You only need 2 connections to the panel The panel Voltage Regulator sends 8 volts to the top of the potentiometer in the gas gauge. The slider goes to ground at the gas tank. You read the resistance from the top [full] position to the slider [how much gas is left] positiom. A very good ground at the instrument panel and at the gas tank sender assembly is required for this to work properly, it is basically an ammeter, not a voltmeter arrangement.

[MikeRL411]

Right. The voltage regulator is in the instrument panel. It's a small metal can about 1 inch by 1/2 inch [more or less] with a printed circuit board visible from the bottom. It has 2 tabs that plug into the instrument panel printed circuit board and a metal tab with a hole for a grounding bolt to the instrument panel board. Regulators for the 410 and 411 sedans and for the 520, 521 trucks and for the 510 are the same circuit wise, the mounting / grounding tab may be angled differently, but a pair of pliers will fix that. Good luck!

[spoolinitup33]

Ok so pretty much, there is one wire that supplies 8 volts to the gauges, then there just needs to be a wire from the gauge to the sending unit, right? And both the gauge and the sending unit need to be well grounded.

[MikeRL411]

Ok so pretty much, there is one wire that supplies 8 volts to the gauges, then there just needs to be a wire from the gauge to the sending unit, right? And both the gauge and the sending unit need to be well grounded.

Exactly! I have been hunting around on this site for an electronic wiring diagram of the 521 that someone posted on this site last month, but don't remember which "bucket" it was hidden in. If you are luckier than me, you might hit it and get the exact pin [and sometimes the wire gauge] to connect to. Again, good luck.

[spoolinitup33]

Exactly! I have been hunting around on this site for an electronic wiring diagram of the 521 that someone posted on this site last month, but don't remember which "bucket" it was hidden in. If you are luckier than me, you might hit it and get the exact pin [and sometimes the wire gauge] to connect to. Again, good luck.

 

Well that shouldn't be too hard. How do you ground the sending unit? I don't know how the ones on 521's look but the one on my 510 just has like a nipple sticking out of it. Also, does the sending unit just work as a ground but limit how much ground the gauge actually gets by resistance? I mean say on a full tank there's no resistance and then at empty there's resistance and that's what makes the gauge move? I need to find a voltage regulator I reckon.

[banzai510(hainz)]

Im going by memory but what I did on my 521 is I took the instrument cluster out and took it to work. I got a varible power supply and put seom voltage on there. I found the traces that went to the gas and temp gauge. I notice when i put 12volts they PEGED OUT. so i started on the low end 1volt and went up in voltage. I noticed it only needed like 6volt or maybe 8 volts like you said to reach MAX on the gauge. So what I noticed that the gauges moved the same exact amount so I figure the VR/temp comp module was OK and then I figured my gas sender was bad. so I went to the fuel tank and notice the vent tube was loose just around the solder ,was breacking apart. So what was happening is the vent tube was shorting out on the sender inside the tank thus causing errectic readings. I JB welded the vent tube straight and no proplems from that.

But lately I have both the gas gauge and Temp gause loose power. so it can be the VR/temp module or a trace that is lopening up in the strument cluster.

 

also where your SENDER goes in the tank the it self grounds when its locked in. There can be corrossion as the tank gets wet and dirty. But be honest I couldnt take that fucker off .

 

 

My 510 s gas gauge has never worked. I swapped out a instrument cluster so figure it is the sender. I have a trip meter and @160-180 miles go to gas station, scared the O ring wont seal. thats why I dont change it

Edited November 25, 2009 by banzai510(hainz)

[MikeRL411]

Found them! Go to http://www.olddatsuns.com/620tech.htm for copies of the 520 and 521 wiring diagrams. For an easier to read diagram, go to this forum http://forum.ratsun.net/showthread.php?t+16339 for a color coded 411 wiring diagram. The fuel gauge and temperature gauge wiring for the 411 are the same as the truck, although some of the truck wire color coding may be different. Since you have said that your original wiring doesn't exist, the routing is what you are after and thanks to one of our contributors you have an easy to read diagram including dash motherboard pin identification.

 

"One of these days" I am going to sit down and compute the proper current flow and build a series resistor and 8 volt zener diode replacement for the mechanical instrument panel voltage regulator. The mechanical units have a bad habit of stopping to work and need a good firm slap to the top of the instrument cluster housing to shock them back into operation [so don't be in too much of a hurry to replace an old one until you have beat on the instrument panel housing].

[datzenmike]

This looks like the voltage regulator for the gauges.

 

 

Note the coil wrapped around the metal strip. It heats up and it bends opening the points and disconnecting the power, the metal strip cools and in bends back and makes contact again. I didn't know the two gauges were mounted together so having the regulator as part of the cluster makes sense.

 

I would guess you need 12 volts to the regulator and the ground is through the tank and temp sender.

Edited November 25, 2009 by datzenmike

[yellowdatsun]

Having owned both 2 521's and many 510's, the gauge clusters are *very* different. Not just the obvious like how they look, but how they operate. I know of the voltage regulator your talking about, and the 510 does not have the same thing. His pics of the gauges are correct, and that's all they come with. The regulator is built in on the board.

 

That said, using the gauge cluster I have sitting here, and the manual, it was pretty easy to figure out what's what. On one side of the fuel/temp cluster the gas/temp regulator gets it's 12v power, on the other side each gauge has a separate connection on the board, which lead to the pin connector. Theoretically you could just wire on a connector to the spot where the two join the board. Or even just wire a connection straight to the leg of the gauge, that whole leg/stand thing is power. For fuel that connection goes straight back to the gas tank sender. I'm doing the same thing, since i rewired my whole car, but I kept the round terminal connector with about 8 inches of wire still attached.

Edited November 28, 2009 by yellowdatsun

[spoolinitup33]

I was thinking someone told me that the regulator was in the gauges themselves. So now, I just need to send power to my gauges and then just put a wire between the sending unit and the fuel gauge.