Speedo problems - Alfa Romeo Forum
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(Post Link) post #1 of 3 Old 03-07-11 Thread Starter
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Speedo problems

Hi Everybody,

I am new to this site.

I live in North London and own a pre facelift GTV (S) reg.

Speedo problems....needle does not rise above 30mph.

I have had the sensor changed but the problems persist.

Any ideas.

Many thanks

RoyGTV is offline  
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Hey Roy, welcome to the forum

I have seen this in another thread on here somewhere I think..., I can't remember what the problem was though, so try the forum search
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Assuming you have a phase 1 ( sounds like it ) the sensor you changed is actually a pulse generator that generates 16 pulses per turn and up to a couple of thousand RPM. If that has been changed it is unlikely to be the culprit. It can however be tested by using a metal file ( have a search here on the forum - the procedure has been detailed before ) to bypass the pulse generator.

Two other possibilities come to mind :

1. The fault is within the instrument. Either the stepper motor or its control circuitry may be at fault.
2. When my alternator failed, the first indication I had was the speedometer playing up as the car's battery voltage dropped ( the charge warning light did not illuminate ).

With the former you're probably looking at a replacement speedo. To dismiss the alternator as a cause, measure the battery voltage with the engine running. You should have 13 to 14 volts. Less than that would indicate the alternator has failed. If the speedo problem is intermittent, you'll probably need a passenger to note the voltage when the speedo is acting up. The cigarette lighter socket is a good source to use for measuring the voltage.
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