Odd electricals
Discussion
Spotted a bit of an issue this morning - suddenlt the voltmeter is jumping up and down in time with any electrical draw. With the flashers on the needle is bouncing wildly up and down, if any other electrical load is applied eg lights then the needle droppes right down the scale and if thers no load seems to be higher, closer to 15 volts than normal.
Not quite sure where to start - can anyone help please
Norman
Not quite sure where to start - can anyone help please
Norman
Norm,
Mine has always "bounced with indicators", but the other symptoms sound like a poor earth or the ballast resistor (IIRC - could be a diode) that stabilises the supply from the alternator.
As said mine sits at around 13-14V normally (at 2500rpm and idle slightly lower once the light has gone out after the first rev), always bounces with indicators and drops to just over 12V with everything on - it definitely follows load though between the 13-14V above and 12V minimum. I thought that was fairly normal and my electrical system hasn't given me any bother in 3 years except for one flat battery after over a month in garage with alarm on (not the cars fault!!)
If you are worried (I am assuming it has definitely changed from the norm and you haven't "just noticed this") I'd get the multi meter out, check the battery voltage across the terminals and see how close it is to the voltmeter at idle and 2500rpm. Check alternator voltage to earth (again at the different revs) and look for a stable supply. I am not an electrician though, but as an engineer I can just about get by with electrics on most occasions so someone else may have a better suggestion
Mark
Mine has always "bounced with indicators", but the other symptoms sound like a poor earth or the ballast resistor (IIRC - could be a diode) that stabilises the supply from the alternator.
As said mine sits at around 13-14V normally (at 2500rpm and idle slightly lower once the light has gone out after the first rev), always bounces with indicators and drops to just over 12V with everything on - it definitely follows load though between the 13-14V above and 12V minimum. I thought that was fairly normal and my electrical system hasn't given me any bother in 3 years except for one flat battery after over a month in garage with alarm on (not the cars fault!!)
If you are worried (I am assuming it has definitely changed from the norm and you haven't "just noticed this") I'd get the multi meter out, check the battery voltage across the terminals and see how close it is to the voltmeter at idle and 2500rpm. Check alternator voltage to earth (again at the different revs) and look for a stable supply. I am not an electrician though, but as an engineer I can just about get by with electrics on most occasions so someone else may have a better suggestion
Mark
OK fellas, mine did this last year at S club and new alternator brushes cured it. Have a good look inside the alternator for wear, especially where the brushes make contact, this can also cause leccie gremlins. Got my brushes from Eastliegh auto electrics for 25 quid as I recall 
On my alternator the brush pack is on the back and held on by two bolts, hope this helps.
steve j
On my alternator the brush pack is on the back and held on by two bolts, hope this helps.steve j
Took it to a local autoelectrician who checked alternator and charging - all OK. Checked earts - all OK, then he traced the power supply from fuses - and found first ff a fuse with dirty connectors, changed that it the pronblem improved greatly - then ran a new supply from the ignition switch direct to voltmeter with an inline fuse. And all back to normal
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