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New instrument voltage stabilizer problems

Discussion in '"Stock" Alpine' started by cliffordalpine, Dec 31, 2021.

  1. cliffordalpine

    cliffordalpine Gold Level Sponsor

    happy new year..i have been a member for quite awhile..but cant figure out how to post...can u help? also, i have a 66 alpine...i have gone through a ton of moss voltage stabilizers...they work for a couple of days..and then suddenly burn up...the wiring harness is new..the gauges have all been reworked by nisonger in NY....everything is properly grounded...i even put original british fuses in the fuse box...any idea what may be wrong? thanks
  2. 65sunbeam

    65sunbeam SAOCA Membership Director Diamond Level Sponsor

    This thread was moved from another one for better attention.
  3. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    I'm not sure why you are burning up the Moss voltage stabilizers. Maybe the Moss voltage stabilizer isn't up to supplying the necessary amount of current in some scenarios. More current is required as the temp sender encounters higher coolant temps and the fuel tank sender is reading a full tank.

    I don't see any capacitors in their design to help smooth things out, but not sure if that is really required. E.g. what if the fuel tank sender is a bit erratic and sometimes cycles between normal resistance and infinite resistance? I have a solid state voltage stabilizer from fellow Sunbeam owner Joe Parlanti (http://velocesolutionsllc.com/Voltage-Stabilzer-Stabilzer-1.htm) that I have used for a few years on my Series V. It appears to have a couple of capacitors under the shrink wrap.

    Here are photos from the Moss site:


    Picture above is of a positive ground item. But I assume the negative ground item also has "B" and "I" connectors and the housing is the ground connection.

    I assume you have negative earth on your Alpine.
    The voltage stabilizer is being grounded by its housing's mounting screw. Any chance the ground connection could be flaky?
    The "B" connection is connected to a wire that is hot when the ignition switch is in the 'run' position.
    The "I" connection goes to each of the fuel and temp gauges.

    Here is the original series V circuit, which you are reproducing with your new wiring harness (possibly with a different fuse scheme...)


    You can double check the gauges by removing the wires and measuring the resistance across the connectors on the gauges. You should see 61 ohms.

    Shannon Boal and bernd_st like this.
  4. jumpinjan

    jumpinjan Bronze Level Sponsor

    I bought one from Moss and inspected it and I think they ask too much. And I also noticed no capacitors for bypassing the input & output leads. Those caps are there to prevent the device from going into oscillations. This voltage regulator is just a simple 7810, 1A, three terminal regulator, that one can but for like 50 cents!
    Shannon Boal likes this.
  5. cliffordalpine

    cliffordalpine Gold Level Sponsor

    thanks for the response....i have the neg ground version from Moss...i bought 8 of them...am down to my last two....i have been using both connectors on the I side...connecting one to the fuel gauge and the other to the temp gauge....they usually work for a couple of days...what happens is at some point when i turn on the ignition and the car starts, the unit begins to smoke...then it is toast...when i take it out it has a strong burnt odor and a white burnt spot visible between the I and B connectors.....
  6. bernd_st

    bernd_st Bronze Level Sponsor

    No experience with the Moss regulators, but what you can do is to connect a Multimeter and measure the operating current between I output and the spade connector of the output cable . If it reads higher than 1A potential is high that you burn up the internal 7820 regulator. Then you need to find the culprit , i.e. either a faulty fuel or temp sensor or faulty wiring ( any shorts to ground ? )...
    Shannon Boal likes this.
  7. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    You may be seeing a brief voltage spike just after starting that cooks the voltage regulator.

    I'd double check the gauges have 61 ohms resistance internally. If they do, then the current requirements shouldn't exceed 1 amp, even if the senders are ground faulted. E.g. 14.4 volts across 61 ohms is less than 250 mA.

    Then I'd try a different solid state voltage stabilizer, such as the one from Joe Parlanti.

  8. AlsPine

    AlsPine Gold Level Sponsor

    Is the regulator getting warm/hot? if so, you might have a short to ground.
    the 7810 or LM340-10 TO220 package should pass 250 ma without a heat sink.
    They should have put something other than tantalum bypass caps on the input and output.
    The proper caps to use are tantalum as they can handle the fast rise time of spikes.
    The drawback with them is when they fail, they go off like a firecracker and produce a lot of heat and a bit of a flame.
    In some cases, when they fail, they can cause a short which would not want it to happen on the input side.
    Attached is a photo of what they look like when they fail on a small switching power supply.
    Perhaps that's why they didn't put bypass caps on these, but they should have at least put a pair of .1uf caps on the input and output
  9. bernd_st

    bernd_st Bronze Level Sponsor

    Design rule No. 1 = No tantalum caps to be used on automotive electronic devices. Better to use normal ones, but with automotive temp range...
  10. Scotty

    Scotty Platinum Level Sponsor

    Got one from Rick and as long as your ground is good, it works very well. The original still works and I have that set aside in case the new one craps out on me.
  11. Pete S.

    Pete S. Bronze Level Sponsor

    I think you're on the right path here. In my experience they do need a heat sink. I made one for my car and this first one failed quickly. On the second one I set the transistor on a strip of aluminum to act as a heat sink. It's been two years and is still running fine.
  12. AlsPine

    AlsPine Gold Level Sponsor

    Yes, I would put a heat sink on it to improve longevity.
    The regulator shown is a 5 volt unit. Just an example of what the regulator looks like with a heat sink.

    Attached Files:

    Last edited: Jan 4, 2022
  13. hartmandm

    hartmandm Moderator Platinum Level Sponsor

  14. Pete S.

    Pete S. Bronze Level Sponsor

    One more thing to consider; When I was an avid builder of 'Heathkit' electronic kits as a kid, I had spotty results with them working properly. The guy at local electronics store that sold me the kits said my Radio Shack soldering pencil was the cause. He said the heating coil near the tip was causing electric spikes that damaged the components.

    He set me up with a Weller setup made for soldering circuit boards and my success rate went to 100%

    Attached Files:

    Shannon Boal likes this.
  15. bernd_st

    bernd_st Bronze Level Sponsor

    Nice soldering station. Looks similar to the one I bought when I was at school. Still using it ;)
  16. Pete S.

    Pete S. Bronze Level Sponsor

    Thanks. I think I bought it circa 1972-73? I still use it too. A great investment.
    bernd_st likes this.
  17. Tom H

    Tom H Platinum Level Sponsor

    Puzzling statement: You say "something other than tantalum ", but the next sentence says "Proper cap to use is tantalum" ?????.

    I assume we would use something the neighborhood of 0.22 uF, so just use polystyrene or polyester caps.
  18. Tom H

    Tom H Platinum Level Sponsor

    6 regulators have gone bad quickly!!! I am thinking something is mis-wired. Have you checked the output voltage at the I terminal when running? Do the gauges work correctly before the regulator fails? The wiring harness is new; is it an original style harness with original color wiring? or is it some replacement type, such as a Rebel harness? Rebel harness is fine, but requires more understanding when replacing the original. I cannot imagine what miswiring might be in place here, but my guess is that there is some excess load on the regulator. Maybe the gauge lamps are wired to the regulator output?? Something simple like that. Are the gauges correct Series III-V type?

    Shannon Boal and Paul A like this.
  19. loose_electron

    loose_electron Gold Level Sponsor


    Above is the specification for the voltage regulator. It should be able to stand 35V max on the input so over voltage on the input is probably not a problem. THe 7810 is good for 1A out. There is another version, the 78S10 that will go to 2A.

    Suggestion - find a 0.75A fuse someplace and wire it in series with the output of the regulator (stabilizer) and see if that fuse burns out instead of the regulator.

    If that happens, you know that something is asking for too much current out of the regulator.

    As for picking a capacitor? If you stick with caps that have a voltage rating higher than 35V you should be good. Polystyrene is overkill for this sort of application. Electrolytic capacitors do have some long term life issues, but I would think either ceramic or tantulum should be good. Depends on what value you need. I would use ceramic if a suitable value exists.

    Try the 0.75A fuse first. That will tell a story.
    Shannon Boal and Paul A like this.
  20. loose_electron

    loose_electron Gold Level Sponsor

    For this setup it's not needed. You got 12V-14V coming from the battery and you are putting out 10V without a lot of quickly changing current demands.

    Since it's a linear voltage regulator, and the current is pretty steady, caps aren't needed. If it was a switching regulator, or there were a lot of heavy and fast current surges required, then a cap would be needed.
    Shannon Boal and Paul A like this.

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