Ok, found the VR and had a general look around to see if I could see any loose wires. Tightened up a couple of loose spade terminals but nothing else obvious. Light still on, went into town. Coming back went over a pothole and light went out. Assumed just the bulb blown but it still comes on with the ignition and went out again as soon as engine started. Weird
Sorted mate - jobs a good `un .... Sorry , Check voltage again , the jolt could have shaken things up a bit and `cured` itself ! (possible with you saying the light goes out on startup .) If it`s hitting 19 still a fault .....
^this. If the battery's still charging at 19V, the regulator is duff and your battery is likely to be dead. The alt light will go out even if the charging voltage is wrong.
Charging voltage should not exceed 14.1V or the battery will start to "gas", loosing water and giving off hydrogen - which is explosive. Eventually it will start to smell of rotten eggs as the sulphuric acid boils away. Replace the voltage regulator and try topping the battery up with distilled water. If you're lucky it'll be ok, but if not you'll need a new battery as well.
Thanks guys, strange thing is the battery needs charging if I drive the bus so nothing getting to it from the alternator? The VR is a Bosch item 0190600017 ADNI/14v will the VW Heritage part no 043-903-803/B work? It looks totally different but says it fits/works without modification. Checked the output again today and it actually goes from 4v to 19v but doesn't stay on any voltage for more than a second regardless of engine speed. Does that still sound like the regulator? Could I fit a newer alternator with a built in regulator and if so what wiring modifications do I need to make? Appreciate your help on this, can't really offer much in return except that if anyone ever needs a VCDS scan on a newer VAG car I will gladly do it for free if you are prepared to travel to me (Cambs). Thanks TA
How are you measuring the voltage? Meter on DC volts setting, measured across the battery, yes? If it's varying that much, implies the regulator isn't working. They are extremely pricey, tho', presumably because ext regs have gone out of fashion. New alt with internal reg a poss - the wiring mods are pretty straightforward. Only prob is getting the old one off!
Wiring mods are easy if you're going for an alt with the internal regulator. It's only got two connections: - thick red (or red/white?) from the screw terminal on the top. This is the B+ supply of current to the battery, and needs to go to the big starter motor terminal (and from there to the battery). - thin blue(?) on spade terminal that goes to the alt warning light. - that's it! You'll have these already in your original wiring (which might need extending a bit).
They often do (mine does), but you can neaten up the wiring to the battery by putting it back how VW made it. One less wire on the battery. It won't be long enough though, the terminals on the wire will have been replaced so many times it won't reach the starter any more, hence it goes straight to the battery which is nearer.
Thanks, during my investigations I have found yet another beautifully bodged bit of wiring Why can't people do things properly? Yes, voltage measured across the battery DC also from alternator output terminal and battery negative.
How right you are, I've already had chassis legs repaired with filler and metal patches made from old tin cans and stuck on with silicone sealant
Right, had enough now. Can't undo the three screws on the inspection cover on the alternator to check the brushes as they appear to have been tightened with a 12 foot long screwdriver before it was in the engine bay. As all three have completely chewed up slots even a screwdriver bit in a socket won't budge them. Clearly they have been undone before at some point and re-tightened with said 12' long screwdriver which has wrecked the slots. Also can't budge screws on voltage regulator as it would appear they too have been subjected to inappropriate torque by some clown in the past. Have decided that since a new VR comes in at the novelty price of nearly double the cost of a new alternator I will buy a new alternator with VR built in and hope that solves the problem. Yes I will have to pay someone to fit it but I no longer have the patience to spend my weekends and evenings cutting myself to pieces on the numerous sharp edges that embellish just about everything, banging the back of my head on the engine lid catch, spending hours with a scrubbing brush removing the oil from my hands and arms or squinting into the darkness of the engine bay which is the equivalent of looking into a coal bunker on wheels.
If you can get the old alternator out, might be worth having it bench tested and rebuilt if needed. You might have a place local to you which does them. Stick "alternator rebuild <your county>" into Google and see what comes up. The voltage regulator might be ok as it's possible you just need a new set of brushes in the alt. Some good info in the link below: http://www.ratwell.com/technical/ChargingSystem.html#testalt I say all this because some of the repro ones aren't exactly brilliant. If it were me, I'd try to stick with an OG one. Good luck!
