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(Post Link) post #1 of 17 Old 09-04-09 Thread Starter
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Hmmm changing speedo

hi all
sorry if this sound supid cos it does in my head but if i buy a second hand speedo does it matter what mileage the old car has done ?
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Re: changing speedo

It will show the mileage on the new speedo. a dealer will write the change over details old/new in the log/service book. There are people who can (or claim) change the mileage in teh new one to match.

The ECU will always have the total mileage the car has covered, so a diagnostic system like AlfaDiag or Examiner will always catch the unscrupulous "clocker" ... unless they change the ECU as well!
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Re: changing speedo

yes because the it will remember the mileage and that will be what is displayed....

there are companies about who can change the mileage legally, i don't know what the cost is or what is required though
 
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Re: changing speedo

thanks for the help. would an alfa dealer not be abel to change it then cos if i brought a new one from a dealer cant imagen they would pu it in saying zero

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Re: changing speedo

Yes they do! A new speedo will go in with 0 or a few miles only showing.

Dealers aren't allowed to ... I think it's to do with "clocking" ... if they can change the mileage who's to say they are changing it to the correct reading. Safer for them to not touch it ...
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Re: changing speedo

i changed another rev counter earlier this year, the new rev counter i bought was with the speedo,temp,fuel clock gauges and all had a silver/chrome thin band around the outside edge (black dials/orange numbers) that my originals didnt have, so i changed the lot.
The new speedo showed just under 2000 miles more than my old one, I havent had it put right, I suppose it might be clocking but in the wrong direction. As it was so little it didnt seem worth it.
 
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Re: changing speedo

as the lads said if the speedo is replaced the REPLACEMENT unit will transfer its mileage with it.

Also, even if its a LOWER mileage speedo the ecu will see another 'odometer re-write'

even on cars with FULL Service History I've seen 2 re-writes.... makes you wonder why?
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Re: changing speedo

sonds crazy why not have the ecu in the dash so whatever speedo you put in it will read the mileage for that car?
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Re: changing speedo

afaik, as the speedo works form the ABS system all the speed/mileage calculations are done on the speedo. less work for the ecu to do
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Re: changing speedo

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Originally Posted by SEARs View Post
afaik, as the speedo works form the ABS system all the speed/mileage calculations are done on the speedo. less work for the ecu to do
The other halves Fiat Bravo doesn't have ABS, yet has a digital odometer. How would that get the mileage reading then?

I would have thought that the speed/mileage would have been calculated from the speed sensor on the gearbox and the system on Alfa's/Fiats would be the same.

Last edited by symon; 09-04-09 at 19:52.
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Re: changing speedo

digial display does means that it works from ABS.

My bro has a Pug Partner van & it has a LCD dispaly, it also has gearbox speed sensor.

if the abs don't work your speedo won't work.
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Re: changing speedo

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digial display does means that it works from ABS.

My bro has a Pug Partner van & it has a LCD dispaly, it also has gearbox speed sensor.

if the abs don't work your speedo won't work.
So if it doesn't have ABS how does it work?

As far as I am aware there are no speed sensors, although it does have the reluctor rings on the hubs, at least on the front.
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Re: changing speedo

no sure, its afiat ... majic???
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Re: changing speedo

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no sure, its afiat ... majic???
Maybe it has light emmiter and sensor underneath that shines on the road, a bit like an optical mouse
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Re: changing speedo

very good :thumbs@ ... could be aworker ... patent that idea asap
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on my old punto i wanted to upgrade the diesel clocks to the sporting type. After enquiries at the FIAT dealer they informed me if I picked one up from a scrapyard they could adjust the mileage to match what my car had on it originally as long as the one i bought showed less milage.

They are able to increase but not lower the reading!
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Digital odometer on our 206 is driven from the gearbox ... no ABS on a 1.4 HDi Style .. on other 206's the gearbox sensor may be blanked off and driven from the ECU, so I guess there is uses the ABS, etc.


Being allowed to increase the mileage on the odometer makes sense ... to lower it is effectively "clocking" .. but what 2nd-hand car sales in their right minds wants to increase the mileage to sell it on?!?


I know someone who used to sell Beemers back in the 70's ... there were allowed to use the new cars to run them in for the clients (!) .. but there was a limit on the miles which was short of his house to ours ... so he used to disconnect the speedo and reconnect it on the way back ... before the days of ECUs and recording the mileage electronically!!!

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