Strange radio problem

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by xerox6135, Jun 15, 2019.

  1. xerox6135

    xerox6135 Member

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    2013 Prius 3. Radio plays fine untill you turn on the parking light and the dash lights dims. At that point the FM reception goes to nothing. Never seen this before and thought maybe someone else has had this problem

    Posted via the PriusChat mobile app.
     
  2. Montgomery

    Montgomery Senior Member

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    Definitely a wiring problem. Or, the radio may be going bad. Just not sure.
     
  3. AzWxGuy

    AzWxGuy Weather Guy

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    Does this happen when the vehicle is in Ready mode? Sounds like a short somewhere, maybe at one of the parking light bulb sockets or the wiring in those locations. Any damage to the vehicle existing or repaired in those areas? Your 12V auxiliary battery might also be weak, especially if it hasn't been replaced yet. Could be 7 years old, and they typically last about that long.
     
  4. ChapmanF

    ChapmanF Senior Member

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    I replaced the halogen headlights with aftermarket LEDs a while back. I like the light, they are very bright, and at last they are able to mimic the geometry of the halogen filament well enough to meet DOT specs, project a sharp cutoff, and be legal.

    But I'm not at all happy with the radio interference they give off. I haven't had time to delve into whether I can add some ferrites, or better shielding, or both. Right now, I have the same symptoms you've got; radio reception that's just dandy until the lights are on.
     
  5. xerox6135

    xerox6135 Member

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    Wow never thought of that. I replaced all my lights with LEDs including the fog lights , head lights ,and running lights . 12 volt battery is 3 years old voltage is 14.5 when in the ready mode 12.4 in the morning . What a bummer 100 percent sure your right. Thanks for the info

    Posted via the PriusChat mobile app.
     
  6. Pluggo

    Pluggo Active Member

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    Now that you know it's the LED lights, just remove them one at a time, beginning with the headlights, until the radio is OK. Hopefully you can leave most of your new LEDs alone.
     
  7. ChapmanF

    ChapmanF Senior Member

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    Just for clarity, the RFI isn't from the LEDs themselves, but from the cheap-nice-person driver electronics they come with. Not that you can really separate the two....

    Ha, I said nice-person before the PC nanny could do it for me.
     
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  8. AzWxGuy

    AzWxGuy Weather Guy

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    Huh, didn't even consider RFI. Wonder what it is in these LED circuits that would interfere with the FM frequency. A basic LED circuit usually only includes a resistor.
     
  9. fuzzy1

    fuzzy1 Senior Member

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    A SMPS (switch mode power supply) driver for the LED can be more efficient than a resistor, provide constant brightness regardless of supply voltage, and allow dimming or adjustable brightness. But a poor design can also put out lots of RFI / EMI.

    Posted via the PriusChat mobile app.
     
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  10. audiodave

    audiodave Active Member

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    I've changed my running, license plate and interior lights to led on my gen 2 with no issues. But I've read of others having problems with the cheap led headlights. I only realized it's a problem from my shop stereo and one LED light in the shop. Once light goes on FM goes to shit. So figured same for the car and sure enough it is.
    Hopefully a reputable led headlight company fixed that.

    Posted via the PriusChat mobile app.
     
  11. Grit

    Grit Senior Member

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    I bought vleds led low beams. No resisters or in-line drivers required so all power goes to the low beams, no frequency modulation interference either. FM is super important to me especially hd radio
     
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  12. ChapmanF

    ChapmanF Senior Member

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    They may not look like they have any kind of driver circuitry, if it's miniaturized so well it just looks like an overgrown cable connector.

    [​IMG]

    It is guaranteed to be switch mode and operating at a high switching frequency, but for the extra money, they can definitely be designed to radiate a lot less RFI. Looking at vleds pricing, they're around 5 to 7 times what I paid for "sealight", and you got what you paid for, a better, lower-interference, driver circuit.

    Me, I still need to get around to hanging some ferrites or shielding tape over mine to see if I can improve the situation any.
     
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  13. fuzzy1

    fuzzy1 Senior Member

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    There must be some form or driver or resistor in there somewhere to prevent the LEDs from frying at the upper end of the supply voltage, and from having too much brightness variability with supply voltage. If it is a high quality switch mode device such as Chapman describes, then near all the power goes to the LEDs, with very little of the power waste of simple resistors, and with very little interference. Lower quality devices will usually emit far more interference.
     
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