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P38 speedo went past max and won't return


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Somehow, due to a bad earth connection on the battery, my speedo managed to go past max, and won't go back... now it's just pushing against the needle from the bottom when driving.

I looked with Rovacom, but couldn't see an option to actuate the speedo needle.

Does anyone know how to fix it? Or is it dash out time?

20210501_192003.jpg

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  • 2 weeks later...

So, to update. It was easily fixed by popping the plastic cover off the binnacle and rotating the needle back by hand.

It also became obvious what happened. There's return spring on the needle, it just assumes you slow down gradually so it returns under power. But when power suddenly cuts out and the needle is past half, it'll fall to the right and won't be able to come back up.

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9 hours ago, missingsid said:

So more like an over centre latch than a return spring?

I meant to type "no return spring"... welp. When you let the needle fall, there is some resistance, which I presume is from the coil driving the needle. But no force in either direction.

8 hours ago, geoffbeaumont said:

I'm bitterly disappointed by this thread. I was expecting to hear tales of hair raising high speed shenanigans in a totally unsuitable vehicle 😁

My apologies, I'll try better next time :lol: Maybe downhill, with a supercharger put on she'll go past 220, most I ever got out of her was 190 ish...

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Odd, a lot of stepper-driven gauges run the motor backwards for a time at start-up to drive the needle home against the stop. You can see it on a lot of cars, the needles will jump back past 0 briefly before starting to work.

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