1955 fuel gauge sender

[rick55]

I have just fitted a replacement fuel gauge sender to my 55 Ford Customline and are wondering abouf the experience of others. The unit i bought was the unit Dennis Carpenter sells which is for 36- 55 Fords 6 and 12volt. I have converted the car to 12volt and am using a solid state voltage reducer for the gauges. I have reversed the polarity of the gauges by swapping the connections on the back of ghe gauge. My question is that the gauge takes some time to register and even with a full tank doesnt show more than 3/4. Is this the experience of others.

[Kahuna]

Rick
I think any new sender will require some adjustment to get the right readings. At least that has been my experience
Jim

[rick55]

The procedure for the sender is specific to fuel tank depth. There is no adjustment in the float arm that i can see. The gauge is also very slow to start reading once ignition is turned on.

[Beav]

Sorry for the long post but it's necessary to reflect the information.

The polarity really doesn't mean anything, at least in reference to the stock setup. Regarding your solid state voltage regulator, well... that might make a difference depending if it can work with reverse polarity. Swapping the wires on the back of a stock gauge will have absolutely no effect.



The gauge works by current heating a bimetallic strip that is connected to the needle. As current flows through the strip it heats up and causes the needle to move as it deflects. In order for the gauge to read correctly and not be affected by voltage and current variances the original sending unit included another bimetallic strip that would click on and off (speed of this action in direct proportion to the current flowing through it) thereby regulating the current and voltage, much like a turn signal flasher. The more current, the more heat and the longer the open time thereby reducing how much current is available at the gauge. The float arm, affected by the fuel level, increased/decreased the position of the point arm thereby altering the duration of time that current was delivered to the gauge and changing the needle position as a result. Now you can see how 6 or 12 volts was inconsequential as it is regulated. Being everything is operated by heating strips, polarity has no more affect than which way a light bulb is connected.

HOWEVER, be very aware of your wiring - I found out my truck's PO made a mistake in his wiring and sent voltage through the sending unit which burned the nichrome-wrapped card. It got hot enough that it melted the plastic the wire was wrapped around. How it never caused an explosion is just luck on his part (maybe even mine, as I drove it from Toledo to Louisville when I bought it.) It must have been submerged in the fuel as I doubt that if it had been that hot in an air-fuel mix it wouldn't have sent one of us on a trip to meet Alice Kramden on the moon.

So... the sending units sold these days do not include the regulator - you have installed one to make up for that. However, the sending units aren't exactly calibrated for us, they're just a kind of a generic make-do/it must be you/it must be your car/etc. product. The resistance coil in the sending unit you have is wound to provide a range of resistance that is close, but not quite close enough, to result in an accurate reading. Using a Kent-Moore instrument gauge tester (J-24538-B) I found the following readings applied to my '53 F-100 (resistance readings verified with a Fluke VOM to all be within 0.1Ω):

Full (needle centered on mark) 18Ω
21Ω
3/4 23Ω
25Ω
1/2 28Ω
32Ω
1/4 35Ω
39Ω
Empty (centered on mark) 43Ω

These readings were taken with the engine idling so as to provide a stable 7.15 volts. I moved to the settings both up and down and from 1/8 spans and 1/2 spans to reach the readings. I've measured both "Must be used with original gauges ONLY" style sending units (standard nichrome wrapped and 'electronic'.) Both measured identically (I wish I had written the measurements down but they were in the 22-98Ω range as my memory recalls.) The spec sheet included with the tester shows Ford fuel units to spec at 10-76Ω but make no mention of years or K-S or CVR type units. My truck has had the dash harness replaced by PO and I've installed a new ground to frame wire. I have the stock (replacement) running board tank ('53) and it measures 11" deep. I made the specific arm length adjustments as directed (DC 'electronic' version sending unit) and ended up exactly in the same place I was with the 'standard' replacement unit. I sped up the engine RPM to allow for 7.56 volts and measured about an 1/8 difference in gauge range as a result. Realizing that the missing regulator in the original sending unit is the reason for the gauge inaccuracy I purchased some adjustable electronic regulators on Amazon for ~$6.

I haven't yet had the chance to install one and report back what voltage and, if necessary, re-adjustment to the float arm was necessary to make it all come together. However, I'm scheduled off next week and, weather permitting, it's on my short list of things to do.

[junkyardjeff]

Did you buy one for 6 or 12 volt?,I picked up a 12 volt sending unit for my 55 but it would never read right so I got one for a 6 volt and much better.

[Daves55Sedan]

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Rick, if you are using this in that Australian Customline UTE, I believe that it uses the wagon gas tank. Although the sending unit for the car models will mount on the wagon gas tank, the float arm for the wagon is much shorter than the one in the cars, due to the shallower depth of the wagon gas tank. Decreasing the length of the float arm will increase the amount of travel that the arm will move from full to empty. Try to duplicate the arm length by measuring the original sending arm. It will definitely help, however, these modern sending units are not very compatible with the old gauges.

[rick55]

Thanks for the replies. What you have all said makes sense to me. The sender is fitted to my 55 Customline Tudor Sedan. I've had no experience with the 55s before this car. My other cars were/are Aust 58 car and ute which are 12 volt and use standard Smiths 12 volt gauges. From what you have said it would be normal for the fuel gauge to be slow coming up to register.
The sender I am using is a Dennis carpenter unit of the correct resistance values that states it is for all fords up to 1955 regardless whether they are 6 or 12volt - so I assume they must have internal electronic voltage correction.
I'm beginning to think that my problem must lie with the solid state voltage regulator I am using possibly restricting current flow too much in conjunction with the similar setup in the sender.
I'll try a factory style voltage reducer from from a 57 onwards and see how that goes.
Interestingly I have used a used sender in the past and that gave all sorts of fuel levels none of which were right . It could read anywhere at any time whether the tank was full or empty and yes I ran out of fuel a few times.

[Daves55Sedan]

Rick, I am pretty sure that those reproduced 1957 voltage regulators are also solid state. They just look like the original unit on the outside.

[rick55]

I might as well stick with regulator ive got.
The other part of my question was the delay before the gauge starts to work. It takes probably 2 minutes before it registers as far as it will go when the tank is full. Is this normal.

[dmsfrr]

Originally Posted by rick55

I might as well stick with regulator ive got.
The other part of my question was the delay before the gauge starts to work. It takes probably 2 minutes before it registers as far as it will go when the tank is full. Is this normal.

Go back to Beav's comment #4 again. Especially the paragraph directly under the diagram.

If I'm reading it right your '2 minute delay' may be caused by the voltage regulator you're using making the voltage too low to let the bi-metalic strips warm up in a 'normal' amount of time. At least that's my first guess.

[Beav]

Weather's been sloppy around here the past few days. With any luck tomorrow and Sunday supposed to be better. If so I'll get to work and let you know what I find out.

[Daves55Sedan]

Ummm...here's some food for thought. I have a '55 Courier that I converted to 12 volts. I used a '56 fuel guage and swapped out the faceplate with the '55 faceplate. I used an original '56 sending unit but I had to get it rebuilt. I did not use the voltage reducer ahead of the power circuit for the fuel guage (as the '56 guage and sending unit originally did not have it) and I did not reverse the polarity. So basically, I duplicated the factory installation for a '56 model.
Some one told me (after the fact) that I wasted my time getting a '56 guage and swapping out the faceplate because allegedly, the '55 & '56 gauges are identical in every way). If that is true (I am not sure, please check) then maybe you don't need the voltage reducer at all.
To answer your question, NO. The guage should begin to register immediately upon turning the ignition key to on.

[Dominic Hide]

'55 and '56 gauges are very different and are NOT interchangeable.
All pre 1956 gauges are 11 ohms resistance.
All post 1956 gauges are 14 ohms resistance.
The 1956 gauge has 40 ohms resistance and will ONLY work with correct original style sender.
These values are true for all gauges, fuel and temp, also oil pressure where fitted. (Mercury and flathead)

[Beav]

Isn't '56 the one and only year Ford used actual 12 volt gauges? Before and after '56 they used voltage reduction, at least on the trucks, I believe.

[dmsfrr]

Originally Posted by Beav

Isn't '56 the one and only year Ford used actual 12 volt gauges? Before and after '56 they used voltage reduction, at least on the trucks, I believe.

I believe you are correct, the '55/'57 T-Birds were originally set up this way too.

'55 (and earlier) gauges were for 6v electrical systems, '56 were actual 12v gauges.
The '57 and newer gauges were labeled "12v" but are actually lower voltage gauges for use in a 12v system with a special voltage dropping regulator in the dashboard just for the gauges.

> edit <
Just in case...
double check your battery ground cable to the engine block AND...
that you have a good clean ground wire from the engine to the body of the car.


.

[Daves55Sedan]

Originally Posted by dmsfrr

The '57 and newer gauges were labeled "12v" but are actually lower voltage gauges for use in a 12v system with a special voltage dropping regulator in the dashboard just for the gauges.

Yes! But my understanding (correct me if I am wrong) of the little constant voltage regulator is that it just has a set of contacts that flutter when voltage is applied and that it is not really a 6-volt resistor, rather a "buffer". If that's true, isn't his 6-volt guage overloaded?

[Daves55Sedan]

Originally Posted by dmsfrr

Just in case...
double check your battery ground cable to the engine block AND...
that you have a good clean ground wire from the engine to the body of the car.

I don't know how they originally obtained ground at the gas tank, since it was originally isolated from the body by rubber pads between the trunk floor and top of the gas tank. And the gas tank straps also have rubber pads, so they insulate the tank from ground.

I ran an extra ground wire from the firewall grounding screw all the way back to the gas tank sending unit and put a ring tongue terminal on it and bolted it directly down to one of the sending unit mounting screws. I tapped that ground wire at the first taillight and connected another wire to ground the tail lamp and backup lamp sockets so that I would never have ground issues with the lights back there also.

[dmsfrr]

Originally Posted by Daves55Sedan

Yes! But my understanding (correct me if I am wrong) of the little constant voltage regulator is that it just has a set of contacts that flutter when voltage is applied and that it is not really a 6-volt resistor, rather a "buffer". If that's true, isn't his 6-volt guage overloaded?

I believe your understanding of the dash gauge regulator is correct, it 'flutters'. It's a high speed electronic switch that opens at a pre-determined limit then continues to open & close to maintain that limit.

Here's why I think the gauge seems to work correctly but takes too long to reach it's level after turning the key on.
The fuel sender in the tank works about the same way as the little dash gauge regulator, it flutters, but slower, to control the electricity thru the fuel gauge.
The fuel gauge needle is linked to a heated strip of metal... (refer back to the paragraph directly under the diagram in Beav's comment #4)
and the 'flutter' rate of the temp sensitive contacts in the sender self-limits the electricity passing thru the gauge. It's also why they should be a matching model year *pair*, the oem '55, '56 & '57 gauges & senders are made to different electrical specs.

I suspect having the dash gauge regulator also in the circuit is reducing the voltage/current a bit too much to allow the fuel gauge to 'warm up' to it's eventual reading in a normal amount of time.

Originally Posted by Daves55Sedan

I don't know how they originally obtained ground at the gas tank, since it was originally isolated from the body by rubber pads between the trunk floor and top of the gas tank. And the gas tank straps also have rubber pads, so they insulate the tank from ground.

I ran an extra ground wire from the firewall grounding screw all the way back to the gas tank sending unit and put a ring tongue terminal on it and bolted it directly down to one of the sending unit mounting screws. I tapped that ground wire at the first taillight and connected another wire to ground the tail lamp and backup lamp sockets so that I would never have ground issues with the lights back there also.

The original fuel tank ground? I don't know either. When I replaced my 55's tank there was nothing to see of how it was grounded except for the worn out & missing cushion strips.
Maybe it was thru the steel fuel line from the tank to the frame, but that seems like a suspiciously bad idea to me.
Installing an actual ground wire from the sender flange to the car body is a much better solution, and is on my to-do list. A previous owner spliced a rubber hose into the steel line out of the tank.

.

[Daves55Sedan]

Originally Posted by dmsfrr

I suspect having the dash gauge regulator also in the circuit is reducing the voltage/current a bit too much to allow the fuel gauge to 'warm up' in a normal amount of time.

By golly, I think you're on to something here. But if he disconnects the constant voltage regulator from the fuel guage and runs a separate wire from the coil terminal of the start switch to feed the guage it means there will be 12 volts connected to a 6 volt guage. Won't it read double the actual amount of fuel?

Originally Posted by dmsfrr

Maybe it was thru the steel fuel line from the tank to the frame, but that seems like a suspiciously bad idea to me.

I think you've hit the nail on the head! It must be grounded via the fuel line connected to the car frame by those little push-in clips. I pondered like you wouldn't believe how it worked, but never thought of the fuel line!

[dmsfrr]

Originally Posted by Daves55Sedan

But if he disconnects the constant voltage regulator from the fuel guage ..... it means there will be 12 volts connected to a 6 volt guage. Won't it read double the actual amount of fuel?

No, because... the fuel gauge doesn't directly read voltage in the circuit. If it did it would swing between full & empty anytime the car was moving.
Instead it reads the heat in the gauge with it's circuit thru the sender, which is switched on & off by the contacts in the sender at a rate that corresponds with the fuel level in the tank.
In theory.... the increased voltage thru the gauge and sender is self-compensating by the temp/current sensitive contacts in the sender.

Originally Posted by rick55

I have converted the car to 12volt and am using a solid state voltage reducer for the gauges. I have reversed the polarity of the gauges by swapping the connections on the back of ghe gauge.

"You do not need to change any switches or gauges. The fuel and temp gauges will work on 6 or 12 V and are not polarity sensitive."
https://www.ctci.org/gilsgarage/6to12.php

I wish I'd found that link a while ago
It's a concise description of what does / does not need to be changed to update 6v cars to 12v,
and why.


Disclaimer: I've only (barely) dealt with this problem once.
My 55's fuel gauge would only show 3/4 full no matter the tank level, the tank was rusting thru and the sender didn't look much better. I replaced the tank and gauge sender pair with a reproduction set from Casco, and the car isn't back together yet.


.

[rick55]

Gee I'm glad I'm glad I've stirred some discussion.
Having driven the car for a couple of trips, the gauge is certainly strange now to say the least. It takes almost 5 minutes for the gauge to reach its maximum reading when driving. The drama continues but, because the fuel level never seems to drop now, which to me from what has been said already suggests that the gauge heater strip is receiving enough to keep the needle pointing to just above 3/4.
I'm about at the point of fitting an aftermarket gauge and sender under the dash.
With fuel gauge sender I took out of the car, which I think was out of an Aust 57 which used 12volt gauges in an identical dash cluster, the needle would register all types of fuel levels depending what it felt like on the day. I ran out of fuel several times with the gauges showing 1/2 a tank. The gauge displayed a full register of movement at various times and would move immediately when the ignition was turned on.
I'm more inclined to think that the sender which is a Dennis carpenter unit built for them by Stewart Warner which is for 6 and 12volt for 32-55 cars is causing the antics of my gauge now, but am reluctant to buy another sender from another source as it may be no better.

[dmsfrr]

Originally Posted by rick55

Gee I'm glad I'm glad I've stirred some discussion.

Well I learned more than I knew before. Thanks Beav for the diagram you posted in comment #4.

Something I was told a while back, before I bought the replacement gauge and sender for mine, but didn't fully understand until this thread.....

For the fuel gauge to have a decent chance of reading the sender correctly...
know they function as a *pair*, and a mismatch may likely defeat you.

The '55, '56 & '57+ each use different that-year-only electrical specs.
Ford built to their own specs, and the after-market folks build as they choose.
Some reproduction parts are intended as a direct replacement for the oem parts, with varying degrees of success.
Other reproduction parts are built look the same, for whichever model year, but are not an electrical copy of the oem parts, and are made to be paired only with the same model year parts made by that same manufacturer, with varying degrees of success.

Add in all the different models, sizes & shapes of fuel tanks & gauges and the limited inventory of:
Used, NOS, NORS, and new reproduction parts for 60-ish year old cars, confusing cross-reference information, not to mention some sellers wanting to make a sale anyway.... and you've got the makings of a real crap shoot.

.

[miker98038]

Just add to the confusion. Some years ago someone called bergmanj had a long post over at Yblocksforever about the 55 gauges. He had extensive documentation, set up, and test procedures. They were King-Seeley products, and the sender fed back to the gauge. The oil and water senders were fixed, but the fuel gauge had adjustments on both the sender and the gauge. I can't find his old post (I think it got lost in an upgrade), and he doesn't show up very often as he's now on a slow dial up connection. Googling it only brings up Willy's and earlier model cars, and some extraneous info. But what you describe is what I remember him posting if you mismatched the sender based on ohm rating. It's also a lot like what happened on my 55 when I added a variable resistor to try to center the temp gauge. The lag in the gauge was quite long, but when it settled down, it was straight up at 180, and just hitting the high line at 220.

[Daves55Sedan]

Once upon a time, I created a tool for recording the position of the sending unit float full and empty positions for the purpose of comparing the positions marked on the tool with the actual sending unit.
I made it out of metal scraps and a cutoff piece of coat hanger to duplicate the float arm. I just bent the coat hanger around in a loop to duplicate the diameter of the float and made the pivot point in the same spot as the sending unit. The measurement is taken by means of a metal strip fastened to the fake float arm with a pivot point so the measuring rod can swivel. The measuring rod needs to be long enough to stick up out of the top of the hole in the tank where the sending unit goes.
I punched two holes in the top of the tool to bolt it down to the tank using the fuel sender mounting screws so that you don't need to hold the top down while moving the measuring stick (and possibly accidentally moving the tool which would provide a false measurement).
To take measurements, push the measuring stick all the way down till the fake float loop hits the bottom of the tank. Mark the top of the stick and the top plate of the tool with a felt tip pen. That represents "EMPTY". Now pull all the way up on the stick till the fake float loop hits the top of the tank. Repeat marking procedure. This will be "FULL" position of float.
Now remove the tool from top of gas tank.
Get a little clamp (paper binder clip can work too). Clamp the measuring stick to the top flange of the tool in the "empty" position.
Collect a bunch of scrap lumber and stack up as needed on garage floor or workbench to achieve a height that will make the floor represent the bottom of the gas tank when the tool is set on top of the lumber stack. Now set your actual sending unit on that same stack of lumber and compare position of bottom of float with the floor (fake float on your tool should be resting on floor). Adjust your sending unit float arm till float rests on floor with arm in the empty position.
Now take your clamp off "empty" and clamp measuring stick to "full" position on your tool. Set tool back on lumber and use a ruler to measure from floor to TOP of fake float loop. Compare position of sending unit float to that same height when float arm is lifted up to the "full" stop point on the sending unit.
If it matches, you are done with float arm adjustment.
If sending unit float is higher than fake float, measure the DIFFERENCE between height of fake float and sending unit float. Divide that distance by one half and bend the sending unit float arm DOWN. This will give you a perfect reading in the middle of the guage when the gas tank is half full.
Do the opposite if the sending unit float is lower than the fake float.
NOW you know that your sending unit float is adjusted properly.

[Daves55Sedan]

If you know that your sending unit float is adjusted properly, now you can test guage.
To do this adjustment, fuel guage must be removed from the dash. Remove the rear mounting plate of the guage to gain access to the two adjustment holes in the back of the guage. A very small straight blade screwdriver is needed to make adjustments. Be very carefull not to allow screwdriver to slip as it could result in damaging guage.
If your gauges are powered from a circuit connected to the coil circuit of the ignition switch, I would remove the power wire connection from the guage temporarily and connect a temporary jumper wire from battery terminal so that all other circuits in the car are dead.
Connect jumper wires with alligator clips from guage wires under dash out to the guage terminals. Use a very fine stranded wire with alligator clips to ground the guage case to the firewall ground.
In order to avoid the need of emptying and refilling the gas tank, you should be able to simply leave the sending unit in-installed and just connect jumper wires from the car wiring to the sending unit. Make sure your connection to the sending unit terminal is not touching the unit case. Run a jumper wire with alligator clips from the sending unit case to good body ground. (if you already have a ground wire for the sending unit, just clip on to it). If not I strongly suggest adding a ground wire for it.

Connect your power alligator clip to the guage terminal and see where the guage reads while moving the float arm to the "full", "half full" and "empty" positions.
If the guage does not read where it should. You need to make adjustments at the back. If corrections cannot be achieved by adjusting the little starwheels in the back, I think you should attempt to find a compatible guage.

PS. when I did this operation, I had the guage sitting upright on top of a short stepladder with some heavy objects holding the wires down to the top of the stepladder so the guage would not move BEFORE attempting to read the guage. If the guage is not sitting perfectly upright and level, the needle may read falsely.

[Beav]

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Not to argue or make light of how you did it but holy cow, that seems to be a lot of unnecessary work. Besides, to make my gauge work correctly with the sending units available today my float arm would have to be twice as long as the tank is wide. Why not just remove the sender and measure the depth of the tank through the sender hole to the bottom. Place the top of the sender under a piece of wood as long (or longer) than the float arm and secure with a screw from the bottom of the sender mounting plate into the wood. Lay the sender on its side and measuring down from the wood make a mark corresponding to the tank depth. Make half and quarter measurement marks. Now attach sender to gauge with jumpers. I'm not much on bending/tweaking 60 year old anythings, one wrong or too many tweaks and poof!, nothing left to work with.

Sorry, but my schedule and the weather hasn't left me much of a chance to move forward on this. I'm responsible for a lot of first responder vehicles and my best made plans don't always pan out. I've got everything I need except time.

[rick55]

I just thought I'd update the drama with my 55 fuel gauge. I replaced my sender with a universal sender from Carpenters that lists as being for 32-55 Fords 6 or 12 volt. Absolutely no change. I sent it to a auto electrician who found that the wires on the fuel and temperature gauges were swapped around. Connected up properly and then found the temperature gauge worked though was inaccurate but the fuel gauge remained pegged on empty. It was a 90-18 ohm sender but the needle never moved even whilst driving. I had an original old sender, put it in the tank and voila!, the fuel gauge works. Seems when I connected the gauges I had a seniors moment and reversed the two sender wire in the harness plug. Certainly explained why the fuel gauge was slow to register and just kept climbing the longer I drove and the temperature just bounced around where it felt like. I replaced the temperature gauge sender with the correct part and it works correctly as well.
I just thought it was the right thing to tell the outcome. Thanks for all the comments. I've accepted now I'm too old to get under dashboards anymore.

[rick55]

I just thought I'd update the drama with my 55 fuel gauge. I replaced my sender with a universal sender from Carpenters that lists as being for 32-55 Fords 6 or 12 volt. Absolutely no change. I sent it to a auto electrician who found that the wires on the fuel and temperature gauges were swapped around. Connected up properly and then found the temperature gauge worked though was inaccurate but the fuel gauge remained pegged on empty. It was a 90-18 ohm sender but the needle never moved even whilst driving. I had an original old sender, put it in the tank and voila!, the fuel gauge works. Seems when I connected the gauges I had a seniors moment and reversed the two sender wire in the harness plug. Certainly explained why the fuel gauge was slow to register and just kept climbing the longer I drove and the temperature just bounced around where it felt like. I replaced the temperature gauge sender with the correct part and it works correctly as well.
I just thought it was the right thing to tell the outcome. Thanks for all the comments. I've accepted now I'm too old to get under dashboards anymore.

[junkyardjeff]

Glad you got it figured out.

[Daves55Sedan]

Originally Posted by rick55

I've accepted now I'm too old to get under dashboards anymore.

Maybe so, but you're still goin to do it anyway, cause whenever somethin goes wrong, you can't stand it till it's fixed, so you'll tackle it until you are satisfied. It's in your blood.

[mike42]

I bought a Carpenter sender for my '40 Ford Sedan. Mine is 6v and it too works very slowly, but when tank is full it goes past the full mark a little bit. It just takes some getting used to, but at least it works. The sender in my '57 F100 and the gauge work backwards. When full it shows empty. When empty it shows full !