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Suddenly, the car is jamming AM radio stations.

Discussion in 'Roadster' started by scotty2541, Aug 6, 2016.

  1. scotty2541

    scotty2541 Member

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    I'm throwing this one open to the community, to see if there are any ideas out there.

    Recently I took my Roadster 2.5 in for annual service, plus they had to dig deep under the hood to replace the cabin blower. That meant removing the aux power supply, which I learned is where the car gets it traditional 12 power.
    Now, the AM stations are awash in Radio Frequency Interference (RFI). And it's not just the car radio. A handheld radio manifests the problem too. That much RFI is likely an FCC violation.

    If anyone wants to watch it in action, here is a video. 6+ minutes of me driving and testing various conditions.


    Here are some important points:
    1. Higher frequencies are worse. 600Khz is less interfered with than 1100 Khz.
    2. When the car stops, (the power generator halts) it stops.
    3. The "tone" of the interference seems related to the motor speed (maybe encoder) NOT power generation
    4. When I try to "coast" by having the power gauge be zero (no regen, or acceleration), the interference is still there.
    5. When I put the car in Neutral and coast, the interference is gone.
    8. This started after, and is almost assuredly the result of, the cabin blower being replaced, and the routine annual service performed. It is NOT something with a bad radio.
    6. This happens to a hand held radio running on AA batteries as well. No connection to the car at all (see next video).
    another 1 1/2 minutes of a handheld radio.

    Tesla replaced the antenna, RF amplifier, tested all connections from the PEM, etc... but the problem is still there. They have come up empty.

    (The radio was replaced with a Kenwood, per this thread. But, as the handheld indicates, it's not a radio issue.
    Replacement of Alpine IVA-NAV-10 )

    Has anyone experienced this? Any ideas where to start looking?

    -Scott
     
  2. gregd

    gregd Member

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    #2 gregd, Aug 6, 2016
    Last edited: Aug 6, 2016
    Sounds to me like they missed re-connecting a ground strap somewhere. That said, my understanding (and experience) is that this car has never had respectable AM (or FM, for that matter) reception. Usually I listen to something streamed from my cell phone via Bluetooth. Did yours actually work before the repair? That seems to be the anomaly, not what you are experiencing now. I wonder what prior fix they inadvertently reversed in the process!

    Has the reception changed (while not driving) for any of the weaker stations? I.e., did the overall signal strength drop, such that the existing interference from the drive train might appear worse now? It didn't seem like the loudness of the interference was worse under acceleration or regen. Mine seems loudest under regen; diodes in the inverter doing their thing... great noise generators that they are. Trying to guess what might have changed... Besides the radio being replaced, is the RF-side of things otherwise stock? Should it be? I.e., was it stock before they fixed the blower? Maybe they put it back the way it "should have been", not understanding that it had already been altered?

    Puzzled here too. And hopeful that whatever fixes it for you might work for others!

    Edit: Just started skimming your thread about the radio upgrade. Really impressive. I'd check to see that all the connections for the antenna path are well seated. Again, a missing (loose) ground somewhere, or the antenna itself may have moved a bit. RF is still an art, in spite of what Maxwell says.
     
  3. scotty2541

    scotty2541 Member

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    As a quick answer... My list, item number 8 (which should have been 6, I didn't renumber when I re-ordered the list :) ) states that it worked fine until the service. Yes, AM has always had a little noticeable interference, but never anywhere near the point that you can't make out what the content is. And now the audio is incomprehensible.
    The RF antenna is still stock. Pretty much everything associated with it is still stock. The radio itself has a slightly better sensitivity than the Alpine, but not significant. So the reception from the newer Kenwood is basically identical.

    As I mentioned, I took it back for them to find the problem, and they replaced the antenna, RF amp, etc... All in areas that were not touched when they serviced it, so I knew none of those would solve it. I maintain it's a grounding issue too, but they insist that the car PEM, and AUX power supply are all reinstalled properly and the same.

    The radio replacement thread isn't mine, but I used it for my upgrade. I did post some stuff about adapting a power supply to run the camera.
     
    • Informative x 1
  4. MLAUTO

    MLAUTO Member

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    I'm not sure why they would say that they needed to remove the Auxiliary Power Supply to replace the blower. The APS is inside the ESS in the rear. If they did remove the ESS and the PEM for some other reason, that would relate more to the motor speed than any of the cabin blower components.
     
  5. scotty2541

    scotty2541 Member

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    Well, I was going by what they told me. The tech said the downconverter that creates the 12V supply from the 400V battery is that box above the fan blower (the black box in my other post that appeared to have pinched the blower cable). If there was a service manual or anything like that on the car, I'd buy one in a second. But no such luck.

    They tried adding an extra ground wire from the radio, through the fire wall, and directly to the bolt that already had several grounding lugs on it. It slightly improved, but not enough to make anything intelligible.
     
  6. gregd

    gregd Member

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    This may be an "is it plugged in" sort of question, but are there any settings in the radio that might have gotten reset during the maintenance? I've seen some rigs that have a "weak station" mode that improves reception under some conditions. I really don't think this is it, but just checking the basics

    Still noodling...
     
  7. scotty2541

    scotty2541 Member

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    Everything got reset during maintenance. I had to re-program all the presets for stations, equalizer, etc. But there is no DX mode setting. The only radio setting is "Analog" "Digital" or "Auto".

    Keep in mind, it does it to a handheld too, which didn't get any reset during maintenance. Mostly because it was sitting in my home office when the car was in for service :)

    I appreciate the 'noodling'.
     
  8. MacroP

    MacroP Member

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    I'm not sure if this helps but in my line of work (industrial electrical) AM radio interference certainly occurs when variable speed drive motor cables are not screened, or incorrectly screened. And the term 'screen' is different to 'earthing' and not to be confused with each other. Shielding is another term for screening. The screening is similar to the one found on coaxial antenna cables but are instead part of large power cables in this case. They don't carry any current but simply contain the EMR/RFI.

    The AM interference issue only becomes apparent when the inverter/drive is actually working hard (not just powered up). The cabling from the inverter to the motor becomes an antenna that literally wipes out any AM radio in the vicinity. I wonder if the power cables from the PEM to the rear motor are individually screened but am unsure how this could have changed with OP's car unless Telsa use an EMI filter perhaps instead somewhere to combat this issue and the filter is faulty or disconnected.

    I'm still not sure how anything could change here with the simple work the OP had at their last service. Will be interesting to know the final assssment if the fault is indeed found.
     
  9. scotty2541

    scotty2541 Member

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    Yes, that helps... because last month when they serviced the car, I was told: " the technician found some washers for the high voltage lines that need to be replaced. "

    In my case, the interference is also when the drive is powered up, but since the system is a synchronous motor/generator, it's probably always producing power, just in different phase.

    I don't know where they are, what they connect to, or if they are associated with shielding, but this makes sense. I kept pushing them about making sure all the grounds were secure. I know the shielding isn't a power conducting ground, but it needs to be grounded somewhere to drain the RF, otherwise they will just rebroadcast it like a Yagi.

    I'm an EE, with some RF experience. As a friend of mine used to say "The problem with RF is the electrons don't stick to the wires".

    -Scott
     
  10. MLAUTO

    MLAUTO Member

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    The tech is mistaken. The only 12V in the HVAC High Voltage Control Module (your "black box") under the hood drives the condenser fans, not the blower. It has a separate 12V fused feed from the APS for fans, so there is no voltage converter inside. The blower is controlled by the HVAC Control module under the center of the dash.

    Just to verify the interference is indeed coming from the rear, mode the handheld radio to the rear of the car and see if the noise gets worse. If you can manage to get the rear of the car up in the air and run it like that you should be able to tell exactly where the interference is coming from.
     
  11. scotty2541

    scotty2541 Member

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    Believe me, I've been thinking about how to use that handheld as a "interference detector". But the car has to be moving for the noise to be generated. I've got to find someone gullible enough to pace me... on foot :)

    Also, the RFI is so overwhelming, I'm thinking I would have to try to triangulate on it from a distance, in order to hear the degree of RFI stepping on the radio signal.
     
  12. MLAUTO

    MLAUTO Member

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    The HV cables from the PEM to the motor are grounded by a single clamp that attaches all three to the PEM, so it's unlikely that is the problem. The encoder cable is one piece with the shield included, but your noise seems to be related to the power side. If they checked the ground to the PEM and found that OK, I would be looking at the PEM itself.
     
  13. scotty2541

    scotty2541 Member

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    The tech told me it was likely the encoder, due to the digital component of the noise. However, he didn't say anything about the cable or shielding. All they pointed me to was the massive braided grounding strap that is under the battery coolant reservoir. I knew that wasn't the shielding we would be looking for, but he kept telling me that's all they had disconnected.

    I don't know where these cable are, I've never taken my PEM apart, or even lifted it out. If the encoder cable was damaged by with the PEM service, or replacing the washers, then we have a good candidate. Now I have to convince them to go back in for a third time... they already had the car for a week trying to find the problem.

    (And the loaner they gave me was a disaster. my commute is about 70 miles round trip, and the 110 charger recovers about 50 miles overnight... So I'm on a loosing battle)
     
  14. MLAUTO

    MLAUTO Member

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    Hmmm- PEM service. Now we're getting somewhere. I would have them remove the PEM again and see what they messed up. I guess they could have left the ground clamp off the motor cables if they don't have much experience with roadsters. That would definitely remove the shielding from them. The washers are on the cables to the ESS and charge port, so that's not the problem.
     
  15. scotty2541

    scotty2541 Member

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    They had the car for 4 days, and wouldn't remove the PEM to see what might have been messed up. But they did completely take apart the dashboard, to inspect the antenna, wires, RF amp, etc... Everyday it was a different part they had to try. Everyday, I would tell them that's not it because of ... Every-next-day he would email me and say "you're right. Now we are going to try ... "

    I kept telling them "First, examine what you touched the last time." They wouldn't do it.

    I'm gonna start making noise. Or more noise anyway.
     
  16. MLAUTO

    MLAUTO Member

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    I'm sure they want to find something else so they can charge you for it. Something they did would be harder to swallow. Thinking about it, I have forgot to install the clamp on the motor cables in the past, but it is always left over after all the bolts are reinstalled. It's a five minute job to check it. It would definitely cause the problem you describe.
     
  17. scotty2541

    scotty2541 Member

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    Especially since they already spent another week on it, and replaced parts that no effect, so they had to swallow them.

    But after spending three grand on it the first time, it shouldn't come back in worse condition than when I took it in. They should be swallowing the additional time to figure out what they messed up.
     
  18. dgindio

    dgindio dgindio

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    The dilemna of car repair: What are they going to screw up in the process of rectifying the problem the vehicle went in to the shop for in the first place. In order to avoid this phenomena, I took every automotive course offered at College of the Desert in Palm Desert. This effort was a great assist in working on the traditional fuel driven automobile. Now I'll need a EE degree to decipher all the systems of a Tesla Model 3.
     
  19. scotty2541

    scotty2541 Member

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    Well, that didn't take long. More like one month, to be specific. The blower motor died.

    So, now I am out over $3K, and the car is in worse condition than when I took it in.

    You'd think they could figure out how to make a car reliably after two and a half models and 5 years...
     

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