Can anyone tell me why the needles on the dials of my wife's 99 reg Focus TDi sometimes, when starting from cold, rotate to the maximum eg the temp needle sweeps instantly to hot on the temp gauge and then after a few seconds resettle at the normal starting position.When it happens, all the dials do it in unison.
It has done this from new and the agent claims they have no cure.
Any ideas (and more importantly) is it damaging !
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Maybe they calibrate themselves? Not so sure if they only do it sometimes, though...
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they calibrate themselves..........
by the way try holding the trip reset button when starting the car - it takes the dash into daignostic mode and you can access various data through the odometer display - temp, fuel load, rpm, mph, etc....
i think it works on all fords with a digital odometer.
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Hi
The focus gauges are moving coil meters. The following possibilities are:
a)On power up there is some form of eletrical fault which sets the dials to full before the microprocessor 'boots up' and takes control. This is unlikely as the 'should' be design to fall to the 'cold' position is there is no processor control.
b) If the actual temperature sensor is faulty the instrument cluster will 'estimate' the temperature by other sensors. It may be that the estimate on startup has some form of 'bug' in it.
It's worth noting that the temperature gauge in the focus is not a real gauge, it is not connected directly to a temperature sensor. It is only an indication from the instrument cluster processor as to what the temperature is.
Interestingly, customer research showed that people where happy when the needle 'was somewhere in the middle'. Therefore the software control will put the needle in the middle and only move it if there is signficant difference in temperature. You may notice the characteristics of this on startup where the needle goes from cold to warm much more quickly than a 'normal' temperature gauge.
Andrew
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It is only an indication from the instrument cluster processor as to what the temperature is.
Where does the processor get its signal from?
In the old days the instruments had a 9v regulator to supply the instruments could the instruments be getting 12v+ for a short period, i cant see why a moving coil meter needs calibrating , in fact i know there dont
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I guess calibrate is the wrong word, Ford describe it as a 'Self Sweep Test' to ensure that all the gauges are functioning, just as it does with the BAS, airbag circuit test.
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That's correct, they calibrate.
Surprised the dealer didn't know about it, but then, maybe not.
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How do they calibrate via this method? i accept car electrical vary greatly from industry but after 30 years in the electrical industry this is a new one.
after initial set-up by either shunt or series resistors no further calibration is required in practice, certainly not every start up, sounds like a fob off?
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i think, though i don't know for sure, that in cold weather the thingy-ma-bob (very technical) that controls the needle movement, looses it's memory and needs to find out what the full scale deflection is.
i've heard it happen on peugeots too, but to be honest never on a ford.
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Many thanks to all for all the info.It is much appreciated
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