First of all my 1955 ford went down the road fine and passed inspection with no problems but the fuel gauge was reading full and I put 25.00 worth of gas in it and temperature read hot but it was not over heating and the radiator felt normal not excessive hot.

I'm brand-new to this site as a member; but, have been lurking for several years now.

I've done extensive work on my own 55 Crown Vic engine temp & fuel guage senders which both work on the same principle.

Both sender AND guage have bi-metallic heat-sensitive 'motors' in them along with resistance wire wound around the 'motor' elements.  The engine temperature 'influences' the sender bimetal 'motor' position, which influences the long-term-average current through both the sender and guage, which then heats the guage 'motor' to the appropriate calibrated position.  The fuel guage works similarly in that the fuel tank sender position 'influences' the sender bimetal 'motor' position, which acts identically on the fuel guage as the engine temperature guage explained above.

These senders & guages are matched-pairs, and cannot be used with any other senders or guages!  They will not work seperately!

IF YOU KNOW WHAT YOU'RE DOING, both the senders and guages can be re-calibrated; I have done just that; but, they must be matched, and you must completely understand the operating principles involved (I have an electrical engineering background - not working int he field now, am a 'Ham Radio operator', previous TV broadcast transmitter engineer, etc. who has been involved with this 'stuff' since about age 6 or 7.

Both the heat sender and the fuel tank sender have calibration screws; and, both guages have two calibration screws each: One for 'zero' adjustment (which is extremely sensitive and very painstaking to 'get right', and one for 'full-scale', which is easier to adjust; but, each is interactive with the other! So, you must go back & forth betweent he two many times.

If you should try any adjustments, PLEASE scribe the initial starting points before making ANY adjustment trials so that you can at least get it back to where it was.

These sender/guage systems are a full 6-volts for original 1955 units; and, are connected in series between the battery posts (use a 6-volt motorcycle battery for 'shop' adjustments).

I hope that this will help.

Thanks,   JLB

55 Ford Crown Victoria Steel Top

Only 2nd time on.  I've put-together a basic 'JPG' diagram with the intent of posting it here; but, am unfamiliar with making attachments.  Help!

Thanks,   JLB

55 Ford Crown Victoria Steel Top

Well, I don't need this but someone will!. Very helpful. Welcome to the site and glad you decided to come out of lurk-dom?



I wonder how many more are out there. Someone could always have something to share.

       A  L  A  N   F  R  A  K  E  S   ~  Tulsa, OK    

JLB,



Very nice write up on the working of the fuel and temperature gauges. A little confused though, my wiring is power from ignition switch to gauge to sending unit to ground (reverse what you show in your diagram). There is only one wire going to the sending unit be it the temperature or fuel gauge sending unit.



Sorry, I can't draw a diagram as nice as yours to indicate what I'm referring to.










Johnson Rod



Southern California

Rod,

Yep, It was a simple very basic drawing to illustrate only.  You're absolutely correct, as my 55 is wired as you say.

In each case, the actual 'second wire' is vehicle chassis ground.

In the case of the original question in this thread, with both guages at their 'top', there is probably a problem with power getting to the guages from the ignition switch; had it been only one problematic guage (especially the fuel guage), I would suspect the ground connection (engine temp. sender would be difficult to imagine having 'lost' its ground; but, fuel tank sending unit losing ground is quite common - either between the tank and chassis, or between the sending unit and tank itself).

Thanks,   JLB

55 Ford Crown Victoria Steel Top

JLB.  Welcome to the site.  Here’s a link that gives more instructions in regards to picture posting. 

 

Picture posting instructions

 

Pay particular attention to the parts about picture sizes.  And all members on the YBF site have the capability of going back into their previous posts and editing which would include adding real time pictures to posts that they originally authored.  Or add pictures to a new post, your choice.

Lorena, Texas (South of Waco)

Thanks, Ted; I will take a look at that information.   JLB

55 Ford Crown Victoria Steel Top

JLB,



I "a simple very basic" person so I took your drawing to mean that you meant that is the way '55's are wired.



Also when there is no power to the fuel gauge shouldn't it read "E", opposite Timmy's case.










Johnson Rod



Southern California

Rod,

My sincere appologies if my first drawing confused you (or others!).

I do believe in the K. I. S. S. (to me, NOT you folks: "Keep It Simple, Stupid!") principle,; but, tend to go-on, sometimes (engineering background -- yes, I know!).  Sort of like the reminder to ask one's self: "Is it plugged-in, is it turned-on, is the fuse (or circuit breaker) blown, is there power at the wall outlet?", before "digging-in".

I've attached a modification of the initial drawing with the guage & sender shown in the correct 'as-wired' order for the '55 Ford. I hope that it helps 'unconfuse' anyone who looked at the first one.

Both guages read 'high' ('hot' or 'full') without power; this guage system is designed that way: Definitely "fail-safe" for the engine temperature; but, definitely NOT failsafe for the fuel guage.

Thanks,   JLB

55 Ford Crown Victoria Steel Top