Speedo shows 17mph more than actual

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geoffps
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Speedo shows 17mph more than actual

Post by geoffps »

Good day
I have a 1998 rev 4 Japanese import. The speedometer shows mph as the main numbers with kph as small numbers so I assume that someone must have changed it as a Japanese car would be mainly denominated in KPH... I think.
I have a sat nav head unit which shows my speed accurately and it reads at about 17 mph less than my speedo shows so if I'm doing 40 for instance, my speedo shows 57.
I'm wondering if the cable gearing is made for a kph speedo so that the speedo needle moves to a position that would reflect the correct speed if a kph speedo was in place but is incorrect for an mph speedo.
Or does anyone know of something else which is causing my problem?

Thanks



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peteV6R5
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Re: Speedo shows 17mph more than actual

Post by peteV6R5 »

if its a 98 then its an electro speedo not cable (cable was rev1s).
if the back plates has been changed then usually then the needles are removed to facilitate the change.
most people cant get it to read correctly after. took me 2 attempts to get mine 100% after putting speedhut dials on.

easiest way is to remove perspex, remove needle. refit unit so everything works.
find private road with no traffic and drive at constant 30mph and put needle back on showing satnav speed.
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geoffps
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Re: Speedo shows 17mph more than actual

Post by geoffps »

Excellent tip, thank you very much.


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geoffps
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Re: Speedo shows 17mph more than actual

Post by geoffps »

Does the needle just pull off and push on?

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shinny
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Re: Speedo shows 17mph more than actual

Post by shinny »

geoffps wrote:
03/06/20 9:25
Does the needle just pull off and push on?
Yes... once you've got perspex cover off.

If you've got a speedo that goes up to 110mph rather than 160 or 180 then someone has already popped the needle off to fit the gauge and obviously screwed up when they put it back on.


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Re: Speedo shows 17mph more than actual

Post by Topdownman »

I have a mk3 and I changed my fascia and had similar issues. I assume the general principles will be the same for a mk2.

The thing to note is that the needle is under tension still when resting against the stop and if you ease it past the stop before taking it off the first time, it will go quite a way before it comes to a rest. I tried to mark this position and replicate it when putting the needle back but still had to remove and replace many times before I was happy with the accuracy.

Petes suggestion above would get round this as long as you are able to get it back on safely and maybe a passenger to help steer would be good!


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geoffps
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Re: Speedo shows 17mph more than actual

Post by geoffps »

Thanks to all for the advice.


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geoffps
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Re: Speedo shows 17mph more than actual

Post by geoffps »

I did as Pete suggested and it is much better now. If I am doing 40mph or more the sat nav and the speedo register exactly the same, that's great compared to how it was.
If I'm going slowly say 31 on the sat nav the speedo says 29. If I'm doing 20 on the sat nav the speedo shows 16, if I'm doing 7 on the sat nav the speedo doesn't register at all.
But... I can easily live with this, most of the time I'm travelling at a speed which is correctly shown by the speedo.
Thank again.
Geoff

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Re: Speedo shows 17mph more than actual

Post by jeff »

are you on stock wheels ?
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geoffps
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Re: Speedo shows 17mph more than actual

Post by geoffps »

Hi
I have 195/55R15 on the front and 225/50R15 on the back.

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