Bench testing rally gauges

Electrical and Ignition

  1. 4spdragtop

    4spdragtop Well-Known Member

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    I know the fuel gauge has ivr in it, I'm trying to see if that gauge and temp gauge is toast. I'm not looking to calibrate, simply looking for needle deflection. I'm using 6v lantern battery, red/positive to "I" post, but should the -ve be hooked to sender/"S" or the "A"?
    Pics attached, the 3 post is fuel obviously, the 2 post is temperature.
    Thanks
    Steve

    20200215_153118.jpg

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    20200215_153208.jpg

    20200215_153224.jpg
     
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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      6 is way too much, Steve. I had an old post I think 3V? Polarity does not matter........Standby........LOL

      .............and I can't find that old thread!!
       
      Last edited: Feb 15, 2020
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      • Dana67Dart

        Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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        My money is voltage acrossed A and I

        You should also have low numerical resistance between A and I (about 10 to 13 ohms. I just tried a 1.5v AA battery an it made the fuel guage read E with 0.12A
         
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        • mvh

          mvh FABO Gold Member FABO Gold Member

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          I was just about to try the same test. My understanding is that the instruments are 5V. I was going to use a model railroad power supply with a rheostat.
           
        • Dana67Dart

          Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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          as long as you do not apply more than ~5 v you should be OK
           
        • Rainy Day Auto

          Rainy Day Auto Princess Valiant FABO Gold Member

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          It is absolutely possible to bench test. It took me forever to figure out how but after I got it, I built my own tester.

          I made it so you can test the gauge by itself or test fuel gauge with an actual fuel sender in the circuit

          CIMG0053.JPG

          CIMG0054.JPG

          CIMG0055.JPG

          CIMG0056.JPG
           
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          • Rainy Day Auto

            Rainy Day Auto Princess Valiant FABO Gold Member

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            I used a 12 volt power supply and then I put a voltage regulator off a parts cluster inline to simulate it being in the car or you can leave the gauge in the cluster and test through there, using the voltage regulator in place already

            CIMG0063.JPG
             
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            • 1969383S

              1969383S FABO Gold Member FABO Gold Member

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              Take a peak behind. If you see black nichrome winding not good! The nichrome should be nice and white colored or slight brownish. For me my fuel gauge looked very nice but temp and oil were toasty black! Thus the new gauges from Charger Specialties. Sometimes the regulator and fuel gauge look decent but! Surely some experts will reply in short order! My Opinion is replace with the modern and upgrade the VR. I will catch rath for this but JMO! I am a happy camper with factory look gauges that work!
               
              Last edited: Feb 15, 2020
            • 67Dart273

              67Dart273 FABO Gold Member FABO Gold Member

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              Steve if you can post a photo of how it sits in the board, with a photo of the board traces I can tell you. I THINK the I is "ignition" and S of course is sender. That would leave A the output of the regulator to jumper over to the other gauges.
               
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              • 4spdragtop

                4spdragtop Well-Known Member

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                Thanks all, heres pics with fuel and temp gauges sitting in a circuit board. I wrote on the board which posts were "I" and which were "S".
                Thanks everyone for the help.

                20200215_222149.jpg
                 
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                • Mattax

                  Mattax Just the facts, ma'am FABO Gold Member

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                  Geez I wuz headed to bed, but saw this. Instrument panel is now moved to the top of the 'to do' list.
                  Here's the cheat sheet I was working on in preparation for this.
                  upload_2020-2-15_23-3-15.png

                  Acc Power comes from the welded splice in the Accessory feed.
                  Fuel Connects to the fuel sender in tank.
                  5 Volts is the IVR feed to the other gages.
                  Temp Connects to Temperature sender on engine
                  Oil Connects to the Oil Pressure sender on engine.

                  Check the colors and positions of the wires on the multi-connector.
                  Too risky to just go by the diagrams without checking.

                  Black should come from the accessory circuit.
                  Everything in this post is referencing 1967.
                   
                  Last edited: Feb 15, 2020
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                  • 4spdragtop

                    4spdragtop Well-Known Member

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                    So to test fuel, put -ve to "A" and +ve to "I" I'm assuming?
                     
                  • Mattax

                    Mattax Just the facts, ma'am FABO Gold Member

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                    See what the others say. I don't think you can drive the fuel sender backwards through the IVR.
                    It looks to me like you can put 6 Volts + on Fuel gage I, with fuel gage S connected to a resistor or a spare fuel sender.
                    6 Volt negative connects to the other side of the resistor or the fuel sender body.

                    Was there capacitor on the IVR output stud or anywhere?
                     
                  • 4spdragtop

                    4spdragtop Well-Known Member

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                    Ivr should be inside fuel gauge. I have tested fuel before with a 6v battery, I should have written it down dammit.
                     
                  • Mattax

                    Mattax Just the facts, ma'am FABO Gold Member

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                    I ask because I saved this photo from the internet - maybe FABO.
                    upload_2020-2-15_23-36-46.png

                    But don't see any reference to one in the books or you photos.
                     
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                    • 4spdragtop

                      4spdragtop Well-Known Member

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                      Yes there is a capacitor
                       
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                      • Mattax

                        Mattax Just the facts, ma'am FABO Gold Member

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                        I'm just going by how its normally hooked up.
                        I've read the IVR works by switching on and off very quickly. That's why I don't know if putting power on the IVR can be done safely or to any good effect. The cap makes sense in that it could help make the output smoother, but again others will know alot more.

                        Going by your photos and the shop diagram, this is what I see. If there's another way to test, I again defer to others with the knowledge and experience. I wouldn't put power through without some device to provide resistance. Is the minimum on the fuel sender zero? or something a bit above that? Hate to see a gage burned by over current.
                        upload_2020-2-15_23-48-12.png
                         
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                        • 67Dart273

                          67Dart273 FABO Gold Member FABO Gold Member

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                          OK what I told you is correct. The I is 12V from the key, S is to sender. The black cap is the jumper, that is the output of the regulator which jumpers over to the other two gauges
                           
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                          • 4spdragtop

                            4spdragtop Well-Known Member

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                            So I assume I can't put -ve to it to check needle movement.
                             
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                            • Dana67Dart

                              Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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                              Mattax's photo in post 15 is on the money.
                              The 5 volts to the fuel guage is internal from it's output, if you apply 5v to a and s on the fuel guage the guage should move.

                              Looks like Chrysler used the same cardboard on the block of all the gauges so A, I and S are meaningless.

                              On fuel, S is sender, I is 12v from ignition switch, A is 5V output to the other guages and itself.

                              On the temp guage, S is the 5V in and I is the sender.

                              On the oil guage (assumption as I have not seen the back of it) S is the 5V in and I is the sender.

                              As others have pointed out polarity is not an issue on temp and oil. It is on fuel.
                               
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                              • Dana67Dart

                                Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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                                The fuel guage has an internal jumper from the output post A to the guage so voltage between A and S will cause needle movement.

                                IMHO +VE to A and -VE to S will get needle movement. Keep voltage below 5v.

                                The capacitor is for noise suppression and point protection from and in the IVR
                                 
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                                • RedFish

                                  RedFish Well-Known Member

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                                  I = input, for this gauge thats 12 volts, A=altered or adjusted voltage , S=sender or signal.
                                  The 2 post gauges use I and A. This input voltage was altered or adjusted elsewhere.
                                  If you had put 5 or 6 volts at the I post of the fuel gauge, it wouldn't harm anything. That mechanical limiter wouldn't function. Voltage through it to the A post? I never tried/tested. It wouldn't be much.
                                  The solid state regulators need a minimum of 9 volts input to function.
                                   
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                                  • RedFish

                                    RedFish Well-Known Member

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                                    A 6 volt high amp lantern battery could cause a crusty gauge to do what it wouldn't do in the car with proper input. 3 volts should get needle movement a tad more than half the range.
                                     
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                                    • Mattax

                                      Mattax Just the facts, ma'am FABO Gold Member

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                                      So it is safe to put 3 volt power source directly across the gages with no additional load?
                                       
                                    • 4spdragtop

                                      4spdragtop Well-Known Member

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                                      Thanks all still on my 1st cup of coffee, so "s" and "i" are +ve, and -ve ? Like I said 1st cup of coffee, and read thru new replies a couple times.
                                       
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