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Something is killing my speed sensor

Discussion in '80-Series Tech' started by carbon60, Jun 19, 2017.

  1. carbon60

    carbon60

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    When I purchased my 1994 HDJ81, the speed sensor was flaky. It would read zero until I was a few minutes down the road, then read normally. It got flakier and flakier until it stopped working completely. So I ordered an OEM sensor, from Taiwan. When I went to replace it, I noticed that the existing sensor was chinesium, not OEM. Huh.

    That was around 20 000 KM (12,500 miles) ago, it has worked great ever since.

    Yesterday, it read zero for the first few miles! WTF?

    Before I replace it with my last spare, what are your thoughts?

    Thanks.
     
  2. Brentbba

    Brentbba Former Golfer SILVER Star

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    Sounds like your sensor is going bad again. Weird that it shows zero and then starts working. Are the connectors corroding? When mine went several years ago, the speedometer just stopped working completely.
     
  3. carbon60

    carbon60

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    Which connectors are you suspecting, the plug on the wiring harness?

    I can't believe it's going bad, this quickly, without a reason.

    Could there be water ingress in my tranny?!
     
  4. DARKNESS

    DARKNESS SILVER Star

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    It's probably just pissed it's in a Land Cruiser. Not the most exciting life for a speed sensor.
     
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  5. CycloSteve

    CycloSteve SILVER Star

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    The question I would ask is if the OEM one from Taiwan was really new. I am aware of the eBay seller who sells these as new, but their reviews suggest that in some cases they are not new, but rather cleaned up take-offs from old rigs. You can get new in the box from Partsouq for a decent price, which is what I would do if the $15 Chinesium one in my rig dies.

    These sensors seem to have a shorter lifespan in hotter climates. My first one died at 175000 miles when driving through Death Valley and Las Vegas in 117 degree heat...it would come back to life for a bit when the temps dropped, but eventually crapped out for good.
     
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  6. carbon60

    carbon60

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    Hah! :rofl:

    Seems like my 6800 lb rig can outrun lighter, more powerful rigs, on gravel. Could be the drivers, though…
     
  7. carbon60

    carbon60

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    That's good info, thanks. I have a second one on hand, from the same seller, which came free because it was lost in the mail for months…
     
  8. carbon60

    carbon60

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    USD150 on Partsouq. I paid $15 or something. Looked perfect, must not have been new.
     
  9. Brentbba

    Brentbba Former Golfer SILVER Star

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    Yes - wiring at the connector to the tranny. Corrosion or loose connector?

    Hmmm...did you get what you paid for? IIRC the speedo sensor I purchased several years ago, OEM from Cruiserdan, was a lot more expensive than $15!
     
  10. gummycarbs

    gummycarbs

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    How do you know the speed sensor is going bad? Did you test the old one? Maybe some other part of the circuit is marginal, like a failing trace on the speedo circuit board.
     
  11. carbon60

    carbon60

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    I'll thoroughly clean the connector and use some dielectric goop, tonight.

    Yeah, OEM seems to be $150 USD, from Partsouq. So the ones I have must be used.

    I tried testing the old chinesium sensor by rotating it with a drill and measuring voltage, got nothing. I also borrowed a sensor from another truck, which immediately corrected the speedometer. I did not test the replacement before installation, but it also corrected the problem.
     
  12. ZackR

    ZackR SILVER Star

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    I got my OEM unit from Rock auto for $145 for comparisons sake.
     
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  13. Brentbba

    Brentbba Former Golfer SILVER Star

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    Sounds like you have your answer!
     
  14. carbon60

    carbon60

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    I meant that history looks like this:

    - intermittent speedo problems
    - speedo dies completely
    - borrow sensor from another truck, fixes the issue, order a "new" sensor from guy in Taiwan for $15 on fleabay (end up with two of them, because one was lost)
    - install "new" sensor, problem fixed
    - two months go by with zero issues
    - issues come back

    The two months it worked well for are what confuse.

    So I still have a second "new" sensor on hand. Maybe I'll get lucky and this one isn't a lemon.

    A.
     
  15. DARKNESS

    DARKNESS SILVER Star

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    Sounds like you bought a cheap aftermarket part and it failed, which is a pretty normal occurrence. If it were me, I'd buy an OEM part and see if that fixes it for good.
     
  16. panamacruiser

    panamacruiser

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    Check the ground that goes to the sensor...you have three cables, one of them is ground...just give it a good ground point and you should have no issues...my rig has 700+ kilometers, is a diesel, and the problem was that only, go to a proper person that works electricity on 12V and they will fins it soon enough...I could send a picture of mine if you wish, but is not pretty as I go to a lot of "places"

    Also, when mine was at fault, the O/D light started to flash...not inmediatly but after the car got up to a certain speed
     
  17. carbon60

    carbon60

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    But how can it be a bad ground, if replacing the sensor corrects?

    I should have mentioned that I also had a blinking O/D light, when the original chinesium sensor that was on the truck when I bought was failing.

    Thanks!