Instrument Panel Regulator

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exect
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Instrument Panel Regulator

Post by exect »

For some time now I have noticed my speedo reading low and have adjusted my driving to overcome this, but I have now realised that most, if not all of my instruments read low. Does anyone know if there is a common voltage regulator?
Its a Xantia 1.9 TD SX 1996
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Post by Peter.N. »

Your speedo reading is not voltage sensitive, its driven by pulses from the sensor on the gearbox. Very unusual for a speedo to read slow, fast yes, the only thing that will normally affect it is oversize tyres or the wrong drive pinion on the diff.
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Post by exect »

Thanks for the reply.
My thinking now is that the pulse amplitude may be low due to connections or dirt etc, but I cant find a sensor on the gearbox, do any of the Xantias use the ABS sensors for the speedo as do Renault?
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Post by CitroJim »

Nope,

Citroen are not cheap-skates and use a dedicated speed sensor (called a VSS) on the gearbox final drive.

The rest of the gauges are noted for their inaccuracy, especially the fuel gauge :lol:

One sure way to check is to get a Lexia on the car and see what it says about engine speed, road speed and coolant temperature and then go, compare.

I would think the instruments will have a basic voltage regulator on board somewhere else the fuel and temperature gauges (being analogue instruments) would read significantly different with with the engine running and not running. I can't say as I've seen one though.

In fact, thinking on, that's a potential test. Note the fuel gauge reading with the engine stopped and headlights on. The start up and see if the reading changes appreciably. If it does then the regulator is not doing a good job and if the gauge does not move then it is doing it's job.
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Post by spider »

They are not (as far as I remember) the usual 780x type 3 pin regulators, if they are they are not labelled as such.

When they do tend to fail (which is rare, and I'll be honest I've only seen it on another make) , the readings (excluding speedo and tacho) only fuel / temp tend to move up and down with rpm slightly.

They will have something on the panel though, the only panel I have to hand (!) is from an Astra of all things, and that has one on, although its got non standard numbers on it unfortunately.

The purpose of the regulator is to supply a steady current / voltage to the gauges mainly.
Andy.

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Post by exect »

My thoughts were that if its a regulator of say 10volts, it would probably be a 9volt reg with a diode in the earth return, and if this diode failed then we would be down to 9v, therfore giving everything a low reading.
If the regulator failed giving the full 12volts then I would expect everything to read high and fluctuate with engine speed.
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Post by Peter.N. »

You will find the speed sensor on the diff housing directly above where the o/s drive shaft enters.
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Post by exect »

Than you all for your input and I will let you know if I find anything.
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