Sending unit gone nuts

[1930artdeco]

Hi All,

So I pulled the sending unit to verify that it works properly before I put fuel in the tank. I pulled it out and positioned the arm for "full" and it went right up to "F". I them put the arm in "empty" and it stayed at empty. Good so far. Then I moved the arm from empty towards full by about 1/4" and it shot to 'Full'. What should I look for on the inside before I open it up? Maybe I bumped something on the inside while cleaning it up, or I may not have gotten all of the shellack off the wires? Also, I am using a diode type voltage regulator on the instrument back for the gauges. Could the ohms be goofing the gauge up?

Thanks,

Mike

 

[Daves55Sedan]

If you need to make an adjustment as to the accuracy of the guage with respect to empty or full, I would take the guage and sending unit out of the car and set them on a wooden bench. Hook up a set of test leads with alligator clips from the car battery.
I measured from bottom of gas tank to top of tank and made a cardboard template. Set the sending unit on a couple of 2x lumber with float arm dangling between the lumber so you can manually move float arm.
Take into account the amount of slant of your gas tank installed in the car and place your sending unit on that same slant by using wooden wedges under the 2x lumber.
Determine first if you need to bend float arm to get the guage needle centered 1/2 way full.
Watch where guage reads when you move bottom of float to bottom of your template. Do same for top of float to see where your guage reads. From this point on, the adjustments needed to get empty and full readings accurate are done by moving thew thumbscrews at the back of the King-Sealey guage. If you are confident that you can screw around with these and get good results, have at at.
I've tried it but could never achieve good results. Send both guaqe and sending unit along with you template and degree of tank slant to one of the auto instrument service businesses like Bob's Speedometer or Williamsons instruments Inc. They can usually fix it up right for you.

 

[1930artdeco]

Thanks Dave. When I sent the speedo unit out he tested the gauges as well. The voltage reducer is the diode type and it may be changing the ohms so I will check that first just because it is the easiest to check. Then, I will check the guts of the sender and then the ground (probably the problem in the first place). After that I will look into bending the arm.

 

[Daves55Sedan]

When i tested mine, I had long green 16gage wires with alligator clip ends. Hook one end to car battery, and other end to metal mounting plate of guage and jumper off of there to sending unit with a second wire with clips.
I think the gage housings are actually isolated from ground when installed in instrument cluster, so you could have bypassed clipping to the mounting plate and gone straight to the sending unit, but I didn't have wire long enough to reach where my sending unit was set up on that lumber.

 

[1930artdeco]

Update:

I Hooked the sender up to the gauge the following way.

6V car battery + to gauge stud
6V - to sender unit body
Wire from sender stud to the other gauge stud

Here is what I observed:
-the gauge moves albeit slowly. This may be normal or old age of the gauge and it just needs to work a bit more.

-E is not the left most mark when the float is down it is the letter E or slightly above. But when I disconnect power it drops down to the left most mark.

-If I manipulate the float to read F, 3/4, 1/2, 1/4, E by looking at the sender the gauge appears to be off. It is off by about 1/8 of a tank.

Here are my questions:
-is the gauge supposed to be this slow?
-is there a way to adjust the gauge or should I try to bend the arm? It seems to only read off when I hit the 1/2 way mark. I did not take any ohm readings. I did this test by visually watching where the arm is in relation to where the arm swings on the sender-see pics.

Thank you,

Mike

 

[miker98038]

Here’s an old link to the early King Seeley gauges. Note the “matched pairs” and adjustments. Bergmanj had a much longer post about adjusting on the work bench but I can no longer find it. They do work a bit slow, and are frequently not as accurate as we’d like. But they’re close enough. I only care when the tank is about 1/4 full- time to find a station. Above that I can live with. For temp I check normal operating temp with an infrared gun, and not where the gauge is. Gets me by, I know if I’m overheating.

http://forums.y-blocksforever.com/Topic22135-1.aspx

 

[Daves55Sedan]

Looks like each setting of the float causes the guage to read a little bit on the high side.
There is an adjustment on the back of the guage that would straighten that out, but I personally would not mess with it myself. That adjustment is VERY touchy and should be done by a pro. If it were my setup and I wanted 100% accuracy I would send both the guage and sending unit to Williamsons Instruments Inc or Bobs speedometer or one of those guys along with a letter telling them that the guage level reads a little on the high side.

 

[Dobie Gillis]

I'm with miker on this one. These old gauges weren't exactly accurate when new. If mine indicated like yours I'd call it good and move on to the next project. JMO

 

[1930artdeco]

As long as I know that the gauge reads a tad high I can factor that into my trip. And like Mike says it is close enough and now I know what it reads so I will make adjustments as needed on the drive.

 

[Ford blue blood]

After a build has progressed to the point where things are getting "checked out" I calibrate the gas gauge by starting with an empty tank. Add 5 gallons of gas, make note of the gauge reading, add five more and note again.

Being old and not up to walking great distances with a gas can the 5 gallon mark is fill up time. Anything outside of that mark doesn't matter!

 

[5851a]

I thought the 57 and up senders and gauges were regular Ford and not the older King Sealy type. They do operate slowly.

 

[dmsfrr]

The '57+ version may still be the King-Seeley brand(?), but with a slightly different design.
The earlier ones used a heat sensitive bi-metal switch in the sensor and the later ones use a variable resistor in the sensor.

 

[rotorwrench]

If it's a rheostatic type (a brush rides directly on the resistor strip) then it may have a lot of wear due to constant friction against the resistance wire. The brush can also wear out. If it works at all then it may just need some cleaning and a very careful check of the brush and resistor parts.

If it's a variable pulsed current type, is may just need the little breaker points cleaned. King-Seeley used both types in the late 50s. They also kept the voltage low after the change to 12-volts. In 56 they tried 12-volts but it just wasn't as reliable as the lower 5 to 6-volts so they added the constant voltage regulators to drop the voltage. The CVRs can wear out too. They pulse current at a rapid rate so the voltage isn't as constant as the modern solid state CVRs are.

 

[1930artdeco]

Rotor-I have the Rheostatic type. It was really shellacked but I opened it up and cleaned it up with a solvent. Is there a way to adjust everything as I didn't look while I had it apart. It does work and I at least know its limitations.

 

[rotorwrench]

The only real adjustment is bending the float arm. The pulsed current type had a resistor and a resistor wire spool that allowed factory adjustment but variable resistor types didn't.