Calibrating fuel/temp gauges

[lalessi1]

I stumbled across an article online that shows how to calibrate older Ford gauges. When I bought my Custom a few years back it was running out of gas with a half of a tank and burying the needle when full. I thought bending the needle was the answer but you can actually adjust the end points of the gauge. The article in the link is for Thunderbird gauges that look different but the adjustment mechanism is the same. I "adjusted" mine rather skeptically and over did it (no surprise). Now my car shows half a tank when full and burys the gauge on empty. LOL. I have not seen anything on the site about this so I thought I would share. The adjustment holes are behind the plate that is held on by the terminal nuts. The point is that you can calibrate the silly things.

http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/gauge_adjusting.htm

[JimNolan]

there's no way to get an accurate reading especially if you run an alternator. What I finally did was run the tank empty, put two gallons of gas in it and then adjust the arm to read empty. You'll notice when you pull the sensor out of the tank that if you look straight down you can see the pick up tube. Mine was sticking up a little and I pushed it back down so it picked up at the bottom of the tank. I would say it works well, well if you like burning half a tank of gas before the needle gets to full and then it does well all the way down to empty with empty being about three gallons of gas left. I never was able to get mine right but empty is the only place I need to know what I got left in the tank. Jim

[lalessi1]

I think I am getting a full range of gauge movement but the 'full" and "empty" indication is skewed one one or the other depending on how these end points are set. It seems I have noticed this in all of the older cars i have owned. Could be my imagination. i just love that there is a way to move the needle on either end with a screwdriver on the back of the gauge. Gotta love this site!!!! 

[JimNolan]

I'd never seen the fuel gauge calibration like the Thunderbird website showed. I'd like to hear from someone that's actually tried it. Also, I forgot to mention that I found out the hard way what happens if you raise the back of the car higher than the front. You run out of gas with gas in your tank, that's what happens. At least it did to me. I'm used to using mine the way it is now so I won't change anything but it'd be nice to know if anyone has succeeded in using a stock gas gauge and making it correct from E to F.

[clusterbuster]

Same thing happened to me. The previous owner reversed the shackles and had the rear end hiked way up. I ran out of gas when the gauge indicated I had some. Tried to reverse the shackles with a long heavy bar up on my lift, and they wouldn't budge. Ended up putting a new set of shackles on to get the rear end back where it belongs. Haven't ran out of gas since.

[petew]

When I finished the resto on my 55 Tbird I was distressed when the temp gauge read past center , warmer zone, when going down the road. The car was actually operating at 170 degrees but looking at that gauge made me crazy. So I took the gauge apart and carefully bent the needle just a little. Now it reads dead center in the gauge when going down the road, problem solved and I'm happy.
Was it the right thing to do ? Perhaps not but it solved the problem !

[JimNolan]

On my 57 I've always ran FE engines and the temp sender was different. So I calibrated it with a resistor. I used a variable resister while monitoring a mechanical gauge at the same time. Now, a quarter of the way up on the gauge is 160 degrees, I/2 way up is 180, 3/4 way up is 200 and all the way to H is 220 I guess. I figured because the other three were linear I didn't have to put more cardboard in front of the radiator and let it get any hotter. Then I soldered a fixed resistor in line with the temp wire. Also to double check the results, the thermostat value you use will validate your results on the gauge. Jim

[hiball3985]

Jim, can you explain this in more detail? "there's no way to get an accurate reading especially if you run an alternator". I run an alternator now and the gauges work fine. I checked the gauge voltage regulator input and output when I had the panel apart for painting. Thanks...

No problem running out of gas on the Ranchero being lower in the front, pick up is in the lower front of the tank..

[lalessi1]

I actually did make the adjustment. It works. I just over adjusted it frankly to see if it would make a difference. It definitely is the way to move the needle to where it should be. the adjusting process is a bit like adjusting drum brakes with a "star" and a slot.

[JimNolan]

Jim, can you explain this in more detail? "there's no way to get an accurate reading especially if you run an alternator". I run an alternator now and the gauges work fine. I checked the gauge voltage regulator input and output when I had the panel apart for painting. Thanks...

No problem running out of gas on the Ranchero being lower in the front, pick up is in the lower front of the tank..

Last statement first:  The pickup on my reproduction gas tank is in the middle of the tank. When you run out of gas and then refill it and it only holds @14 gallon of gas you realize something don't make sense. What did make sense to me is I flipped my spring hangers to raise the rear of the car a few weeks previous and since bringing it back down after buying new springs I can attest I have put 18 gallons of gas in it before on a trip. Just made sense to me.
First question: How do I know that the fuel gauge will read different with different voltages applied to the circuit. Just makes EIR sense when dealing with DC circuits. The same way I know my headlights are brighter using an Alternator that supplies 14.5 volts when the generator only supplied 13.5 volts. Now if you decide to use a gel-cell battery those voltages should be higher still. Gell cells require still higher charging voltage. The same resistance (80 ohms) used with a 13.5 volt system compared to a 14.5 volt system will indicate about 8% difference. I'm generalizing these statements but thru experience they are generally correct.

[hiball3985]

Interesting, I thought the voltage regulator for the dash gauges would retain the same fixed output voltage ( Appros 6V ) regardless of the input voltage. Sometime I will dig out an old one and test it using a variable amount of input and check the output..

Most people don't know that things like headlights and other accessories are actually 14V, they just call them 12V for simplicity when 12 volt systems were developed. If they hadn't done that we would all be changing headlights/tail lights etc. every week..

[JimNolan]

Interesting, I thought the voltage regulator for the dash gauges would retain the same fixed output voltage ( Appros 6V ) regardless of the input voltage. Sometime I will dig out an old one and test it using a variable amount of input and check the output..

Most people don't know that things like headlights and other accessories are actually 14V, they just call them 12V for simplicity when 12 volt systems were developed. If they hadn't done that we would all be changing headlights/tail lights etc. every week..

You've got to remember that the battery has nothing to do with your lights, instruments etc. The battery is just there to start your car and let you listen to the radio until it runs down. lol 
As far as the test with the voltage regulator on the old fords are concerned, I've never made that test, assumed there would be no reason too since it was a bi-metal contraption that worked from current to oscillate. Thus more voltage, more current, more oscillation. Please make that test. I would like to know the results.

[JPotter57]

I calibrated mine by replacing them with mechanical gauges   

[BP57CUSTOM]

I need to try this calibration on my fuel and temp. The fuel currently would run out at about half way. and the temp shows to be a little on the hot side.  The temperature gauge on the wall of my garage said it was 21 degrees this morning BRRRRRR

[lalessi1]

Before adjusting...during...