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Testarossa Speedo pegged sitting still

Discussion in 'Technical Q&A' started by speedmoore, Jun 23, 2008.

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  1. speedmoore

    speedmoore Formula 3
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    Apr 15, 2003
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    #1 speedmoore, Jun 23, 2008
    I was test driving a Testarossa on the way to have it inspected when the speedometer pegged at some 200 HP and the odometer revolved the mileage like it was doing that speed.

    Turned around and went back to the shop, disconnected sender and went back to inspection station to get the car smog test and passed.

    Back at the shop, checked the sender and installed a spare....same problem.

    Anyone seen this?

    We also had just replaced the fuse box (TR's are notorious for burning them up). We put the old fuse box in and the problem still there so not sure if related at all.

    I don't want to run the car much as it raked up over 150 miles turning back from the inspection to the shop to disconnect. So troubleshooting with voltmeter needs to be quick. It does it idling in the shop.

    If anyone has seen this problem, I sure could use some help.
     
  2. mwr4440

    mwr4440 Five Time F1 World Champ
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    #2 mwr4440, Jun 23, 2008
    Try "Search."

    Someone here (I think, maybe other forum) recently had the same problem with a 3x8 as I recall. It racked up miles EVEN WHEN SITTING STILL and NOT RUNNING, not key in ignition. Do not recall the fix, sorry.
     
  3. speedmoore

    speedmoore Formula 3
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    #3 speedmoore, Jun 23, 2008
    I did try search but nothing of note on old or current Fchat.
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #4 Steve Magnusson, Jun 23, 2008
    What about when stationary with the key "on" but engine "off"?
     
  5. Telerding

    Telerding Formula Junior

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    #5 Telerding, Jun 23, 2008
    I knew those things were fast just sitting still!!
     
  6. speedmoore

    speedmoore Formula 3
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    #6 speedmoore, Jun 23, 2008
    Last edited: Jun 23, 2008
    I'm sad to say we thought we had the problem resolved with some aftermarket "scotch loc" radio wiring but the problem came back. Tapping on the console cluster has it jumping around so now we the instrument pod out looking at the connections and trying to test the speedo.

    I called MoMa and they claim to have not seen a speedo/odometer peg problem.
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #7 Steve Magnusson, Jun 23, 2008
    Last edited: Jun 23, 2008
    Would have to say 80% chance something internal with the speedo and 20% chance bad ground (since you've ruled out the sender). Since "tapping" the cluster helped -- when the other gauges (oil, water temp) are reading a reasonable value, and you turn the headlights "on", do the needles move up suddenly a fair bit? Would also indicate grounding trouble -- and the grounding of the cluster relies on a very long (and "iffy") mechanical contact path IIRC (e.g., loop terminal on painted stud/surface).

    What about my other question? Key "on" and engine "off"? (or is it just too unrepeatable in any mode to make a conclusion?)
     
  8. speedmoore

    speedmoore Formula 3
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    #8 speedmoore, Jun 23, 2008
    Last edited: Jun 23, 2008
    Car has to be running and wheel has to initially spin then pegs.

    I took the speedo over to Overseas Speedometer that repairs a lot of our Porsche gauges. Unfortunately they are very versed only in VDO for the Pcars as well as the others like BMW and Mercedes.

    However, at least I was able to use their pulse generator. I could not get the thing working at all and then it finally did and then it pegged.

    Went back to shop and put it back in along with a 512BBi speedo I had on the shelf in working order (it uses same sender). I ran them both at the same time in parallel with the same wires from the car and the original TR speedo pegged while the BBBi speedo read about the speed we were spinning the wheels in gear.

    So it seems it is internal with the Speedometer itself. We cleaned all the connections before the final test using Stabalant 22 with no difference.

    I'm not sure if MoMa can fix if they never heard of this problem before. Any ideas for quick turnaround repair?
     
  9. rimoore

    rimoore Formula 3

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    #9 rimoore, Jun 23, 2008
    That just happened to my 348. I send out my speedo to Palto Alto Speedometer and they did a two day turnaround for $214. They even rolled back the extra milage.
     
  10. speedmoore

    speedmoore Formula 3
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    #10 speedmoore, Jun 24, 2008
    I sent it off to Mo-Ma earlier after talking to Joey who knew exactly the problem unlike whomever I talked with the day before.

    We'll see how they compare to Palo Alto.

    thanks

    d
     
  11. Testarossa Lover

    Testarossa Lover F1 Rookie
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    #11 Testarossa Lover, Jun 2, 2011
    Hey guys, I need some help...

    Speedo issue I have sounds about the same as yours.

    At first it bounced and a month later it died.

    I had it repaired and working fine and all the sudden it started hitting 80-90MPH while I had ignition on and car parked. After driving the car at 80+ and reaching 95 it was reading 95 and holding at that speed with no problems. I hit 105 and it held 105 I slowed down to 70 and it stayed at 80-90.

    So, I had it looked again and repaired. It worked fine and 200 miles later, it died. Two days later I got in driving around town and suddenly it went back to working at normal speed and now it is dead again. :(

    Sending unit was replaced at first when it started to bounce.

    Any idea?
     

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