Fuel sending units

Roger Harmon
Roger Harmon Expert Adviser
edited November -1 in HUDSON
When you guys substitute donor fuel tanks into your 6v + ground system, did the fuel sending unit require any modification?



R/ Roger.

Comments

  • Unknown
    Unknown
    Roger

    The system does not care if it is + or - ground and many say that you can operate the fuel gauge circuit on 12 volts, however, it may reduce the voltage controllers life. I would use a "volt-a-drop" unit (reduce to 6V operation) in the circuit to correct this issue. With a 6V operation this is not a problem, but a non-Hudson fuel tank and sender must have the same total resistance value as the OE sender for the gauge to operate correctly.

    Fred
  • Ol racer
    Ol racer Senior Contributor
    FYI

    I converted my Terraplane to 12V and my stock gas gauge works, but kept the Dash Gauges 6V by using an 'IV Voltage regulator' from a 60 -80's Ford car or trk.(Its tiny like a circut breaker) .Available at any Auto store..

    However on another Hudson I couldnt find a good sender so I bought a universal Sender & Gauge from JC Whitney for $20+
  • Unknown
    Unknown
    A while back it was determined that the fuel gauges and sending units were not even voltage sensitive, but operate on the amps. Yes units need to be matched for maximum accuracy but I've found that if your bigest concern is when it's time to head for the pump this is'nt neccessary, just get the float adjusted to read close on the empty side.
  • Park_W
    Park_W Senior Contributor
    When I had the dash out of my Hornet and was converting it to 12v, I did some bench testing of the gauges, using a precision power supply. With the original Hudson instrument voltage regulator (IVR) and the tank unit at the middle of its travel, the gauge read about 1/4 tank higher on 14v than it did on 7. Replacing the original IVR with the one for early 12v Fords brought the 14v reading right back to where it should be. Regarding 37T2's comment above, I have to differ ... in virtually any DC circuit, while the current ("amps") may be considered as what's doing the work, that current is a result of the voltage applied to the circuit. So it's a toss-up whether you want to say the behavior is voltage-dependent or current-dependent. These gauges work on an "time-average current" basis. If you apply higher voltage, the greater current causes the pulsating make-and-break mechanism in the gauge and/or in the IVR to keep the circuit open longer between pulses. That's why the gauges don't read twice as high on 12-14v as they do on 6-7v. But as my tests showed, they do read somewhat higher.
  • Roger Harmon
    Roger Harmon Expert Adviser
    O.K.,



    But if I find a tank at the junkyard with acceptable dimensions, it'll have a 12v sending unit. Will the resistance in that tank unit be too high or low, or are the 12v units compatable with our 6v dash units?



    R/ Roger.
  • Walt-LA
    Walt-LA Senior Contributor
    Park,



    What is the operating voltage range of the gas and temp gauges on the '51's? I tried an Ecklin IR-2 on my temp sending unit with no success.... but could be the Ecklin part was bad. Have been looking at the Standard VRC-604, which can get at Car Quest- but they want $ 59.60 plus tax here! Believe it only drops 12 to 6V, so was going to run my present Hudson regulator in series with it. Niehoff makes one too- believe current part no is VN33771, which drops 12 V to 5-8 V. But can't find locally.



    Have also been running Hudson 6V circuit breaker since converting to 12V with no problems. But can get 12V in same amps for about $7.00. Think I may change that. Think it would be worthwhile to do so?



    Thanks,



    Walt-LA
  • Park_W
    Park_W Senior Contributor
    Walt, the IR-2 was what I used in my bench tests and what I put on the car, replacing the original Hudson IVR. Did you really mean you tried operating just the temp gauge from the IR-2? If so, that could be the problem, as the current draw of just the one gauge would cause the IR-2 to behave differently. It would not "see" enough current to cycle as it's supposed to, so probably wouldn't bring the gauge reding back down where it should be. Neither the original IVR nor the IR-2 actually regulate voltage, so they're really mis-named. Instead, they are a kind of circuit breaker that makes and breaks the circuit to provide an average current for the gauges. This was done to make the gauge readings somewhat insensitive to the minor changes in voltage from the battery vs. the generator. I recall seeing some Hudson or other tech note that said the voltage was around 5v, but I think that's just saying that the average current produced by the make-and-break IVR is equivalent to what you'd get if you applied 5v to the gauge circuit without the IVR. On the circuit breaker question, there's no need to get a "12v" breaker. These breakers, as do most, operate purely on the amount of current going through them, so the voltage applied to the circuit is not relevant to the breaker itself. There's no difference between a 6v and a 12v circuit breaker of this type. It's the amperage rating that counts.
  • Walt-LA
    Walt-LA Senior Contributor
    Park,



    Thanks! I did try the Echlin unit on only the temp sender, and didn't get any reading. I've been running the car on 12V for 2yrs with no problems on gauge readings with either temp or gas- wonder if might not continue? but idea of a nearly sixty year old part in a position so hard to change once the dash is back in place is not comforting. Am using one of the Ford light truck senders with float rod adjusted to reflect empty, and it works fine. Full shows as full too.



    Am wiring dash out of car, so is accessible now. Saw somewhere the recommendation of an Echlin IR 4 for gauges in '54 chev. Also spoke with tech rep at Standard Motor Products. He could not give voltage output of either Standard VRC 604 or Niehoff UN 33771 (both same from catlog photos). Said price was high because they are "getting rare"... shades of rear axle bearings...



    Walt
  • Park_W
    Park_W Senior Contributor
    Walt, I would think that if you tried a good IR-2 with just one gauge, you'd certainly see the gauge respond. That does indeed sound suspicious. Back a while someone on the forum said he'd tried several of the other IVRs, and none seemed to work well. I wonder why NAPA has dropped the IR-2? Probably just a slow mover. When the fuel sender in my '51 went bad, I installed the one Dennis Carpenter sells for some of the Fords. It's working well.
  • Hudson Grandpa
    Hudson Grandpa Expert Adviser
    Park W.



    I installed the Dennis Carpenter sending unit in my 54 cpe. Instrument gauge works so mechanic says. No readings. Grounded unit to frame.

    Grounded tank to frame. Nothing. Wire from instr. gauge to tank hot.
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