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  • OT car lamp electrical question

    Hi Group,

    I had a dash lamp go bad, so I ordered LED for all of them since it is a bit of work to get to them to replace, and should save me ever going in again. Well they all worked great except the turn signal lamps, they did not work at all. The rest of the turn signal system worked, I could hear the flasher, the front and rear lamps all worked, So the question is, were these little miniature wedge base LED lamps #37 style not the correct ones, or is it what I've read before, that LED and conventional mixed together will not work ?

    Look forward to some discussion on this so I and others can learn from my experience and mistake.

    TX
    Mr fixit for the family
    Chris

  • #2
    It's possible that the LED is not getting enough voltage. Some devices are powered through the indicator lights. When the device flashes it conducts through the bulb and it's possible that less than 12 volts reach the bulb. That would not bother a hotwire bulb too much, but it's possible that it lowers the LED Vf below the 3.3 volts or so that it needs to light up.

    Old time flashers used the current flowing through the signal bulbs to heat a bimetal strip that clicked back and forth. You knew you had a bulb out when it started flashing twice as fast or twice as slow, depending on the design.

    Can you find the originals and check the voltage and watts?

    Dan
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

    Comment


    • #3
      LED turn signal lamps often don't play well in vehicles that did not come with them from the factory. It has to do with the difference in amp draw between incandescent and LED bulbs. Replacing the turn signal flasher with one specifically made for LED bulbs may fix the problem. You may have to replace the actual signal light bulbs at the front and rear of the vehicle with LED units so that every thing is compatible. Super Bright technical help can tell you how to fix your problem.

      https://www.superbrightleds.com/carb...php#HyperFlash
      https://www.superbrightleds.com/cont...technical-help

      Comment


      • #4
        If I read the OP correctly, the turn signal system does work, and the actual problem is that the dash lights do not follow the working of the actual turn signals.

        If that is the case, the flasher etc would not be the problem, the issue would be something about how the dash lights are powered.

        One immediate consideration is that LEDs are sensitive to polarity, where regular filament bulbs are not. If for some reason, the polarity of the dash indicator light sockets on the turn signals is reversed from normal, the LEDs might not work even though the original filament bulbs do.
        CNC machines only go through the motions.

        Ideas expressed may be mine, or from anyone else in the universe.
        Not responsible for clerical errors. Or those made by lay people either.
        Number formats and units may be chosen at random depending on what day it is.
        I reserve the right to use a number system with any integer base without prior notice.
        Generalizations are understood to be "often" true, but not true in every case.

        Comment


        • #5
          I wonder if they need to be bipolar in that application-

          I wonder also about the rest of them- do they have to be inserted the correct way, or did you just get lucky and most of them went in the correct way- or are they designed with a bridge rectifier so they don't have to be inserted in a particular way.

          At any rate, the comments about turn signal lights are correct- most often in older vehicles the flasher relies on the current level through the bulbs being at a certain level. You get around this by adding a parallel resistor to simulate the correct current draw. I had to do that with my bike when I revamped the rear lighting to use all leds.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

          Comment


          • #6
            LED lamps are polarized. One connection must be positive and the other negative. Wedge bases that I have seen can be inserted two ways. For a filament it does not matter. For an LED it does. Did you try just rotating them 180 degrees?
            Paul A.
            SE Texas

            And if you look REAL close at an analog signal,
            You will find that it has discrete steps.

            Comment


            • #7
              I would think that the #37 wedge base bulbs are polarity sensitive and that the other dash bulbs are a different type. Those bulbs are either not polarity sensitive, (they are available), or they are in a mount the precludes the polarity sensitivity.
              I can see putting two wedge base led lights in wrong, but the other bulbs all working indicate that polarity is not an issue in their case.

              It sounds like the external turn signal lights are still of the incandescent type so this will have no bearing on the system flashing or not, especially since this not the issue.
              When switching over to external led turn signal bulbs the easiest way to circumvent the operational issues associated with the lights not flashing due to lower current draw is to replace the flasher to the type recommended for led light use. Much easier than adding resistors to simulate existing incandescent bulb current draw.
              Home, down in the valley behind the Red Angus
              Bad Decisions Make Good Stories​

              Location: British Columbia

              Comment


              • #8
                Hi Guys,

                Thanks for the suggestions. From what you have told me and I did Google this last night, you are correct on the incompatibility of the LED and the incandesent lamps. The polarity issue did not matter with these LED lamps, as I replaced all 10 in the instrument panel and they worked except the turn indicators, none were oriented in any particular way and they are all the same #37 wedge base lamps and sockets. I also got some #161 for the dash as well and they did say polarity specific on the package, so I did have to test them before closing the dash back up. When I did the others it was not a problem so I went with it but didn't test the turn signals until I was all done.

                ​​​​​​​So the answer to the problem sounds like the flasher and the rest of the external turn signal lamps all need to be LED to have a complete LED system, or stay with the Incandescent system in all locations. For the time being I have gone back to the regular lamps for the turn indicator lamps to drive the car this week, but when any of the exterior lamps go I'll do the whole thing in LED then.

                Great discussion, I appreciate the help in this matter.

                TX
                Mr fixit for the family
                Chris

                Comment


                • #9
                  At least in Europe, turn indicator relays need a certain amount of power drawn by the lamps. In this way it can detect that you have a defective lamp by changing the frequency of the flashing. Leds wont load the circuit enough.

                  The same with the charging lamp that needs to excite the alternator.
                  Helder Ferreira
                  Setubal, Portugal

                  Comment


                  • #10
                    When I still fooled with such things, they had a "high power" flasher available, designed for multiple turn signals such as added trailers. I think they operated on voltage to ground and would flash even with no load.
                    http://pauleschoen.com/pix/PM08_P76_P54.png
                    Paul , P S Technology, Inc. and MrTibbs
                    USA Maryland 21030

                    Comment


                    • #11
                      Hi Guys,

                      Here is what I have found out is needed to use LED lamps in a incandescent turn signal car lighting system. Hopefully this will help others should they go this route and have a problem.

                      https://www.jegs.com/p/JEGS/JEGS-LED...72412/10002/-1

                      TX
                      Mr fixit for the family
                      Chris

                      Comment


                      • #12
                        Some alternatives:

                        https://shop.advanceautoparts.com/p/...el12/5081289-P

                        https://www.amazon.com/Heavy-Compati...2526665&sr=8-1
                        http://pauleschoen.com/pix/PM08_P76_P54.png
                        Paul , P S Technology, Inc. and MrTibbs
                        USA Maryland 21030

                        Comment


                        • #13
                          Does not seem as if the dash lamps would be causing an issue if the flashers are working correctly now. The current for the filament dash lamps is small, the turn signals are typically over an amp per each, not going to make much difference, and you say the turn signals work.

                          There might be a small difference in the flash rate, not sure anyone would notice that.

                          It's possible that the lamps just are not compatible with that location, different voltage etc, but if that were the case, the regular turn signal dash lamps would presumably be a different part.
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

                          Comment

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