Homemade VREG for solid fuel gauge reading '67

[msampsel]

Well Nissanman challenged me offering his help a few days ago ... so ...

I got out my semi conductor vreg and built a couple of my own.

First used one which was rated at 8 volts a 7808 from Fairchild semiconductors.
It read 6.8 volts when I applied 12.4 volts to it. As expected my fuel gauge read too low.

So on to the 7809 vreg. It read about 7.8 volts at the output. Results are in the pictures ...
First pic is fuel gauge steady at ~ 3/4 tank, reading a little low I think ... oh well for now
Next is pic with key off ...
Next is the new vreg ...

Red input from the yellow wire in the roadster and green output to the Y/G wire in the roadster.

Black to ground

I sure wish the dad gum place inline operation worked for me. But alas it does not

[spl310]

Now to fit it in the stock can...

[dbrick]

Is there a variable regulator available?

[garth]

Is there a variable regulator available?

There are quite a few available. I bought a dozen or so postage stamp sized Vregs for $0.50 each. PC board mounted with a tiny potentiometer to adjust voltage from 0.01-11.4 volts. It will fit in the stock Nissan Vreg can too. I will post pics when I return from vacation.

[msampsel]

Yeah, Leave it to the vacationing Hockey fans to find the best solution!

I think the fuel gauge itself is adjustable. And 8 volts is pretty close to were you need to be.
So after I get my windshield on and valves adjusted and a full tank I will post the gauge level.

Of course if the variable ones come already PC mounted with potentiometer and will fit in the can ... sweet ...

[23yrRebuild]

I think the fuel gauge itself is adjustable. )

It is indeed adjustable...I needed to tweak mine to read the way I wanted it to. There's an adjustment screw for empty and one for full. I drained the tank, letting the float hang all the way down, turn on the ignition to see where empty reads on the gauge, then added 1 1/2 gallons, and adjusted the empty screw back to to where it read empty, then filled the rest of the tank to the spec'd capacity, 11 gallons IIRC, and adjusted the full mark on the gauge. My gauges were restored by our beloved Jon Frampton, and they came out beautifully, I just felt I needed to know what empty really meant. I know the same effect can be achieved by trial and error bending of the float arm, but I thought this way was easier, and I wanted to know what these adjustment screws were about anyway. They're also found on the oil gauge. Jon, if you read this, feel free to chime in with any do's or don't's regarding this method of gauge adjustment...

[msampsel]

Some good info thanks. Rather than drain the tank the sender
can be removed and then hang down all the way. Depends on your druthers
This of course assumes it is in same position when empty

[23yrRebuild]

Rather than drain the tank the sender
can be removed and then hang down all the way. Depends on your druthers
This of course assumes it is in same position when empty

I thought about doing it that way at first, but figured I would need to ground it with a jumper pigtail or direct contact somewhere on the body, and I didn't want to blow myself up with an errant spark,...I've done that before .... it hurts... a lot...and I wanted to calibrate the gauge to read empty, while I actually still had 1 1/2 gallons left.

[caraddict]

I think the fuel gauge itself is adjustable. )

It is indeed adjustable...I needed to tweak mine to read the way I wanted it to. There's an adjustment screw for empty and one for full. I drained the tank, letting the float hang all the way down, turn on the ignition to see where empty reads on the gauge, then added 1 1/2 gallons, and adjusted the empty screw back to to where it read empty, then filled the rest of the tank to the spec'd capacity, 11 gallons IIRC, and adjusted the full mark on the gauge. My gauges were restored by our beloved Jon Frampton, and they came out beautifully, I just felt I needed to know what empty really meant. I know the same effect can be achieved by trial and error bending of the float arm, but I thought this way was easier, and I wanted to know what these adjustment screws were about anyway. They're also found on the oil gauge. Jon, if you read this, feel free to chime in with any do's or don't's regarding this method of gauge adjustment...

I know it's a major pain but the way Mike is calibrating his gauges is by far the best way to achieve the most accurate indication so I wouldn't change a thing. The only thing I might add is that you may need to go from the top to the bottom a couple of times because any adjustment you make on one end of the gauge will usually have about a 50% effect on the other so you basically go back and forth until it's pretty close to perfect on both ends. (Most people only have the patience to make sure empty is good and I can't say I blame em.)The bummer about our cars is that everything affects the accuracy of the gauges including the lead length of the wires / how well grounded the sending units are and of course the ever popular voltage regulator so the bottom line is that any time you change the indicator / the sending unit or the voltage regulator then you should do yourself a favor and go through the calibration procedure you described cuz no two cars or gauges will calibrate the same.

Jon

[msampsel]

@23yRebuild and @caraddict too

Well sounds good, I just hate to mess around with draining gasoline if I can help it.
I plan to calibrate the upper end with various filllups etc and mileage checks etc el.

If I do go for your: "Cadillac, Ferrari, Roll Royce, Bugatti or Roadster" method (one of these is politically correct)
it needs to be once my suspension changes are done.

Great to get the best possible way in writing though. Thanks guys

[23yrRebuild]

The only thing I might add is that you may need to go from the top to the bottom a couple of times because any adjustment you make on one end of the gauge will usually have about a 50% effect on the other so you basically go back and forth until it's pretty close to perfect on both ends. (Most people only have the patience to make sure empty is good and I can't say I blame em.)

Jon

Jon, I do seem to recall following your advice on doing that procedure, I know I didn't just turn each screw once and call it good, it did take a bit of fussing, but it wasn't hard. Thanks for refreshing your expertise on this.

[msampsel]

Well I took car to get filled up with the gauge like this (pic below) and 8 volt homemade Vreg running.
Took 8.9 gallons to fill.

So I guess 1/8 tank on gauge is 3 gallons of fuel (or 1/4 tank) this seems like a good enough safety net for me.

8 volt homemade Vreg is good enough ... I know I need to adjust my wiper switch nut ... sigh
And the clock needs its guts fixed too ... I have Nissanman's clock wizardry bookmarked ...

[Curtis]

One of our local guys told me on the clock is first make sure the motor runs. If the motor runs then all they usually need is a good clean and lube.

I checked my gauge by using an extra sender outside the car. That's how I found out that it is the sender in the tank that is the problem. Used the VW sender I modified as well to see how it works.

http://www.311s.org/phpBB3/viewtopic.ph ... er#p213677

[msampsel]

old thread revival:

Well I'm ordering a set of resisters and am going to use them to set my gauge. I found my gauge reading empty when I have 4 gallons left, (the resistance level at the gauge was approximately 60 ohms, which made sense, ~ 25 ohm increase for each drop of 1/3 rd of tank gets you from 10 ohms full to 85 ohms empty close to the 90 ohms in the wiki diagram). So I adjusted the gauge to about 1/3 of a tank which I estimated from the resitance and a good old stick in the tank.

Too much paranoia (empty with 4 gallons) so ... The little adjustment wheels in the rear are stiff so it's too easy to go from empty to a full tank with 4 gallons. Hoping the wheel on the empty side is for the low reading and the one on the full side is for the high reading. After getting the low side to read correctly, fill up pegged the gauge, so resisters are on order.