temp & oil gauge not working

Discussion in 'Electrical and Ignition' started by terry, Oct 26, 2018.

  1. terry

    terry Well-Known Member

    Messages:
    455
    Likes Received:
    2
    Joined:
    Jul 7, 2005
    Location:
    moorpark,california
    View My Photos
    Local Time:
    7:05 PM
    well I have after market gauges on my 68 barracuda and never tried to hook up these 2 gauges. amp and fuel gauge work fine. but the temp and oil pressure gauge will give a
    test light a blinking light when I connect the wire to the test light and the key on. if I leave the test light connected a little longer on the temp sender wire the gauge will move. but the oil gauge will not. any idea's? new harness and sending units.
     
  2. 67Dart273

    67Dart273 Well-Known Member

    Messages:
    37,712
    Likes Received:
    5377
    Joined:
    Oct 14, 2010
    Location:
    Idaho
    View My Photos
    Local Time:
    5:05 PM
    1....Go drum up a wiring diagram and closest you can get to a factory service manual over at MyMopar. You may have to settle for a Dart EG. This will be somewhat DIFFERENT than your ralley dash

    2....Are the aftermarket gauges electric and did someone tap into the factory sender wires? Your clue is to look in the bay at the engine senders. If the factory wires are hooked to the oil/ temp sender, then they have been cut under the dash

    (I don't know where you are connecting your test lamp?) "The wire??"

    3...On a ralley dash, the three gauges, oil/ temp/ fuel all have the save voltage source from a regulating device IN the fuel gauge, so it is evident that it is working. That power comes OUT of the fuel gauge on a third stud on the rear of the cluster and jumpers over to the other two gauges by means of the PC board traces. It might be a simple as the trace being broken/ burnt, OR THE NUT on the gauge stud has become corroded

    4...There are test resistors by which you can test the gauges, and there are hundreds of posts on this board about them

    A search

    67dart273, gauge tester - Google Search

    An example

    Help with Temp, Gas, Oil Alt gauges FREE VIDEO INCLUDED!

    5...Also PLEASE READ this thread on PC board repair, as it gives you insight into "whut" 'kin go wrong:

    Printed circuit pins repair
     
  3. 1969383S

    1969383S FABO Gold Member FABO Gold Member

    Messages:
    3,599
    Likes Received:
    1111
    Joined:
    Jan 8, 2012
    Location:
    Cumming, GA.
    View My Photos
    Local Time:
    8:05 PM
    Are these the newer gauges from RT specialties?

    If so they look like these.

    245330ED-A403-44CC-A490-6EF68E53FF8C.jpeg
     
  4. 67Dart273

    67Dart273 Well-Known Member

    Messages:
    37,712
    Likes Received:
    5377
    Joined:
    Oct 14, 2010
    Location:
    Idaho
    View My Photos
    Local Time:
    5:05 PM
    ^^The plot thickens?^^

    OP it is IMPORTANT to tell us the details of what you have
     
  5. 1969383S

    1969383S FABO Gold Member FABO Gold Member

    Messages:
    3,599
    Likes Received:
    1111
    Joined:
    Jan 8, 2012
    Location:
    Cumming, GA.
    View My Photos
    Local Time:
    8:05 PM
    Hope so! Have been very pleased with these!!
     
  6. terry

    terry Well-Known Member

    Messages:
    455
    Likes Received:
    2
    Joined:
    Jul 7, 2005
    Location:
    moorpark,california
    View My Photos
    Local Time:
    7:05 PM
    yes mine do look like those but they are the original gauges. my after market gauges are both mechanical style. and work fine.
     
  7. 1969383S

    1969383S FABO Gold Member FABO Gold Member

    Messages:
    3,599
    Likes Received:
    1111
    Joined:
    Jan 8, 2012
    Location:
    Cumming, GA.
    View My Photos
    Local Time:
    8:05 PM
    Ok so you still have the originals in the cluster? Mine are aftermarket replacements that are almost just like the originals. Assuming no one has messed with the original wiring or modified the 5v regulator in the fuel gauge then Chances are they looked like my originals and were toasted. Oil pressure was always 80 or more and temp was always around 220 or more. Likely they are bad. If your fuel gauge still functions well then the built in regulator is likely still functional or at least marginal. Explains the pulsing you see. Sounds just like what my 69 was doing. I would recommend what I did and replace them with the upgraded original style looking units if that is what you want. I did not want aftermarket gauges under the dash or wherever and wanted the cluster to work great. Here is my what my original OP and Temp gauges looked like inside. No wonder they were inacurate. My fuel gauge nichrome was still nice and white colored.

    CC2B9735-6B11-4070-9D3C-C73587DDDAEB.jpeg
     
    Last edited: Oct 26, 2018
  8. 1969383S

    1969383S FABO Gold Member FABO Gold Member

    Messages:
    3,599
    Likes Received:
    1111
    Joined:
    Jan 8, 2012
    Location:
    Cumming, GA.
    View My Photos
    Local Time:
    8:05 PM
    I can tell you sooner or later the regulator in the fuel gauge is going to fail! These gauges from charger specialties re-act so much faster and accurately! The kit is pretty easy to install with a few caveats, and looks great and very hard to tell they are not original.
     
  9. RedFish

    RedFish Well-Known Member

    Messages:
    22,162
    Likes Received:
    1330
    Joined:
    Sep 5, 2007
    Local Time:
    8:05 PM
    I've seen and serviced a few hundred of these thermal instruments.
    95% of fuel gauges toasted ( due to their function and duty cycles over many years ), 60% of oil gauges toasted, 20% of temp' gauges toasted.
    Here's a somewhat common scenario that sheds some light on that oil gauge percentage.
    The original terminal for the oil sender looks very much like a female spade terminal. It slips over a button like contact atop that sender. If the female terminal had a plastic isolator on it, it didn't last very long ( it's a rare sight today for sure ). This bare terminal would often get bumped off the button like contact and land against most anything close creating a short to ground.
    A 0 ohm resistance path isn't good for a 80-10 ohm instrument. sigh
    Todays solid state regulators produce more stable output voltage at much lesser amperage so a short circuit at sender side doesn't fry an instrument nearly as quick as the OEM mechanical limiter could/would.
    Even though the output voltage is routed to 3 instruments, current always takes the path of least resistance. We can't begin to guess what resistance the fuel sender and temp sender offered while the oil sender wire offered 0 ohms.
    In the end I've typed a few facts that may or may not explain what your diagnosis reveals. Good luck
     
    • Like Like x 1
    • Agree Agree x 1
    • terry

      terry Well-Known Member

      Messages:
      455
      Likes Received:
      2
      Joined:
      Jul 7, 2005
      Location:
      moorpark,california
      View My Photos
      Local Time:
      7:05 PM
      thanks for everybody's great input. well today with the help of a service manual I traced the 2 wires ( oil pressure & water temp) thru the bulkhead (still blinking) up to the round connector that fits into the circuit board for gauges. the wires did blink as I tested them in the round connector. I have not pulled off the connector BUT what I did not see was the usual voltage limiter anywhere. the only device I have in that area is a round condenser looking device that has 1 wire that plugs into the circuit board next to the water temp gauge and it has 12 volts when the key is on. is this my voltage limiter. looks nothing like all the squire limiters that I see with 2 wires.
       
    • 67Dart273

      67Dart273 Well-Known Member

      Messages:
      37,712
      Likes Received:
      5377
      Joined:
      Oct 14, 2010
      Location:
      Idaho
      View My Photos
      Local Time:
      5:05 PM
      YOU HAVE NOT BEEN LISTENING. Please re--read this thread carefully. The limiter in a Ralley dash IS INSIDE the fuel gauge
       
      • Agree Agree x 1
      • 1969383S

        1969383S FABO Gold Member FABO Gold Member

        Messages:
        3,599
        Likes Received:
        1111
        Joined:
        Jan 8, 2012
        Location:
        Cumming, GA.
        View My Photos
        Local Time:
        8:05 PM
        That pulsing originates from the third post on the fuel gauge. Not surprised you see it at the sender connections and through the bulkhead. Sounds normal but!
        That is a radio noise condenser and it plugs onto one side of the three prong fuel gauge. “Like said “ the voltage limiter is built inside the fuel gauge. You can have your gauges rebuilt or replace them with more modern quick re-acting units and a newer electronic limiter. Your choice of original style cluster gauges or aftermarket mechanical units installed as you please. A-body Rally dashes are not the same as the lower models. There are several options available to keep the original and have a updated electronic regulator. You just need to decide what way you want to go. I choose to go fully new old look in the cluster and are very happy with my decision!
         
        Last edited: Oct 28, 2018
      • 67Dart273

        67Dart273 Well-Known Member

        Messages:
        37,712
        Likes Received:
        5377
        Joined:
        Oct 14, 2010
        Location:
        Idaho
        View My Photos
        Local Time:
        5:05 PM
        He needs to do some troubleshooting and figure out what is actually wrong first.
         
        • Agree Agree x 1
        • terry

          terry Well-Known Member

          Messages:
          455
          Likes Received:
          2
          Joined:
          Jul 7, 2005
          Location:
          moorpark,california
          View My Photos
          Local Time:
          7:05 PM
          yes it bothers me but I did find that with a test light I get the blinking coming out of the fuel gauge circuit board stud that travels to the temp harness pin. in fact I think I have 3 studs that are blinking and 2 others that are hot. I just may start at square one and us a volt meter on the wire that connects to the water temp sensor and see what voltage is says.
          terry
           
        • RedFish

          RedFish Well-Known Member

          Messages:
          22,162
          Likes Received:
          1330
          Joined:
          Sep 5, 2007
          Local Time:
          8:05 PM
          The limiter produces a pulse voltage. A digital volt meter will flash 2.XX and 3.XX. That voltage travels through the winding of each gauge and should appear at gray wire out at oil sender, purple wire at temp sender. So take a volt meter to the engine bay. If you don't find pulse voltage at the sender wires, Something is wrong upstream. Wires in wrong positions of bulkhead connector, loose attaching nuts behind the gauge, failed gauge, etc...
          If you prove pulse voltage at those sender wires, you prove all upstream is working.
          With switch off attach a sender wire directly to ground. At switch on the corresponding gauge needle should travel to its highest position in a smooth motion and quite rapid rate. Keep this test brief since this zero ohms path can overheat the gauge. At switch off the needle should travel all the way home about the same as it went up. Not a swiss watch slick movement but fluid like enough to satisfy. If a needle hangs, jumps, or doesn't travel the full distance in either direction... faulty gauge.
          If all proves good the fault must be at senders. They do need chassis ground and too much Teflon tape on their threads might interrupt that ground path.
          Wrong sender ? The oil sender meant for a oil warning lamp will not work a oil gauge.
          A varying resistance through proper sender to chassis ground causes heat in the gauge that moves the needle. So next test would be run engine with sender wires disconnected ( and isolated from ground of course ) and use ohm meter to find what ohms signal the senders are making. You would have to wait for hot water before the temp sender shows something within the 80-10 ohms range. Thermostat opens at what 180? 195? That's somewhere around 35 ohms.
          If you know you have oil pressure the sender should show less that 80 ohms right away. For example... approx' 14 ohms is approx' 60 psi and approx' the 'U' in PRESSURE on that gauge screen.
           
          • Like Like x 1
          • Agree Agree x 1
          • 67Dart273

            67Dart273 Well-Known Member

            Messages:
            37,712
            Likes Received:
            5377
            Joined:
            Oct 14, 2010
            Location:
            Idaho
            View My Photos
            Local Time:
            5:05 PM
            OK let's step back a bit. Earlier you said you have "aftermarket gauges." You did not explain this. Are you talking about typical under dash add on gauges, or did you find something that replaced your original in-dash gauges.

            Going around testing for blinking and voltage does you no good if you don't know what you are looking for.

            You need something for test resistors to replace the senders OR get one of the senders so that you can measure it's resistance and know what to expect.........see my earlier thread........ There are three known resistances in the old factory test box. This is in the shop manuals, the box, that is. One resistance produces the "low" scale reading, the second produces "mid" or 1/2 scale, and the last produces full scale. These readings are same whether fuel/ oil/ or temp gauges. If they all read off about the same, you likely have IVR problems which I repeat ONCE MORE is inside your fuel gauge.

            If one or two is off or by differing amounts, or all three by differing amounts you have OTHER problems and possibly IN ADDITION to an IVR that is bad

            Best thing to do is piggyback a SOLID STATE replacement IVR onto the fuel gauge and disable the internal one. Do a search. There are websites that detail this. And you must be careful

            If that does not fix the problem, and one gauge reads different with the same test resistor, then that gauge has a problem or the CIRCUIT TRACES AND CONNECTIONS to and from that gauge.

            If you get all that to work correctly, then worry about body wiring and individual sensors......which again, you can test at the sensor / wire connection with test resistors