Hi guys, got another question for anybody who can help....been trying to find a fix to a minor fault I've got with my speedo (1992 JDM 2+2 TT). When I power on the ignition (but not firing it up) the speedo rises to just under 10mph. It then seems to read this distance higher at all speeds as I am driving....downloaded GPS speedo app for my iPhone and checked with TomTom. Does anybody know what might cause the needle to rise like this before I even start moving/fire it up? I'm ruling out the speed sensor (maybe wrongly) on the grounds that the cogs aren't even turning when this happens. The clocks are obvs not JDM because they show mph to about 110 with kmh inlaid also (so not stick on dails). Is there a way to calibrate the speedo down by 10mph ? The other odd thing is that although the speedo is a MPH unit the odometer is clocking up in kms still and not miles. I was thinking of just getting a set of second hand JDM clocks (they seem loads cheaper than uk ones) and fitting one of those add-on converter units....

If they only go up to 110 mph then they have had the dial face replaced, as stock they go up to 180 mph if uk and 180 kmph if jap.

 

In order to change the face you need to pull the needle off . If you put it back on wrong then i believe you can get the effect you describe.

 

There is a write up on here or one of the american forums about how to do it properly which i used when i did mine

I have had this issue in the past and it came down to a duff speedo convertor, check to see if you have one wired into the back of the dash, or it could be the dials you have (110mph) are to blame.

If you can get a set of uk clocks, it will eliminate the need for a convertor and will rid you of the 112mph limit.

Cheers. I thought about trying to move the needle, but it rests at zero when ignition is off, so not sure if that could physically be done.....might hang out for some UK clocks then, but they're fetching £90+ on fleabay

UK clocks arent cheap, but you save £25-£60 on a new convertor, depending where you get it from, ebay or zcentre and they are plug and play up to a series 3 iirc, so in the long run worth doing, its the best move i made, after trying a couple of different sets of JDM clocks.

Ok, just had a thought, if the dial face has been replaced, that explains the kms odometer issue.....they've just had the mph speedo face stuck over and are prob still the original JDM unit......therefore will prob not have the converter unit if that's the case....

Yes, changing to 120 mph faces is done so you dont need a converter, it leaves the odeometer reading in km. it also leaves the jap 112 mph speed limiter in place

If you do decide to try moving the needle, a fork makes a good tool

 

I'm fairly sure the instructions i had said to put the needle back on with the clocks powered, but it was a few years ago

Thanks Ian, might give that a try then as an interim fix. Wasn't aware of it being limited to 112mph tbh, but it has a very bouncy back end that I'm looking to fix at the weekend with a pair of coilovers off a scrapper I've sourced. That has put paid to any top end thrashing so far.....plus I'm not near any public roads, for the benefit of the tape!

Just had a thought about this issue; if I tweak the needle back 10mph, the clocks will prob work correctly. If I then fit a speedo-converter/de-limiter which will fix the odometer and 112mph issue, what will happen to the speedo calibration? Will what was once km/h now be referenced for mph? If so would I then need a new dial overlay as the km/h on mine are the smaller numbers underneath the big mph digits, so would prob be confusing (so would be better to do everything while clocks are out?)

Moving the needle under load will most likely damage the spline on the motor, moving the needle not under load, ie out of the car and no power (ign off) then it will be hit and miss as to the correct position.

mph will read the same as kph with a convertor, as you say the the larger numbers that were a kph marker are larger than a mph face would be and as only the 20 and 40 etc is on the kph face you would see 30mph as just a line rather than having the number next to it.

 

It is possible that someone has had a play with the clocks in the past which is why the needle moves forward 10mph upon start up or ign on and you can try to knock it back by 10, but be prepared for a fubarred speedo if it doesnt work.

My thoughts on 'tweaking' the needle was to remove/disconnect speedo, move the needle to 30mph (for example) grab the needle spline tightly with needle-nose pliers, twist back plastic speedo needle to 20mph.....is this likely to work or will the plastic speedo needle not lend itself to moving on its spline?

The plastic needle has tiny ribs inside the centre, which aids its mount to the spline of the speedo, so forcing the needle against the spline might damage the needle. If you can get the needle off, put the clocks back in the car and wire up plugs, then turn the ign on, then replace needle over the spline at the stopper. Before you put the dash back together, give it a test, if its still out, try again with plan B lol

I have a few speedo spares so if it all goes tits up, you can have a replacement dial.

Cheers, I reckon the needle nose pliers might still work then. I know they're about 10mph out, so if I do as described previously ( turn needle to 30mph ) but instead of twisting back, pull needle off the spline and (keeping main shaft in same position with pliers) then replace the needle in the 20mph position.....