whiskychaser

You are very welcome. Good to hear you got it sorted. Thanks @Keliuss for the kind words too

Instead of tear arsing between lights and roundabouts and slamming on your brakes, my guess is that you are reading the road and driving at a fairly constant speed. To the inexperienced, driving smoothly may appear to be driving slowly. But it is not. As Jackie Stewart said 'Good driving for me is smooth driving'. And he was no slouch. The problem arises because idiots fail to recognize good driving when they see it. The same sort of idiots overtake in fog then suddenly hit the brakes because they can't see anymore

Yes, the handbrake has a simple switch to ground. That is what makes the circuit to put the light on so is perfectly normal. The other brake light warns of a fault with the braking system such as low brake fluid. Not suggesting that the BMW garage does not know what they are doing. I'd just be concerned at driving the car for any distance with the voltage so high. If I had to guess, I'd say there is a problem with the rotor. The exciter voltage does not seem to be getting through it and back to the regulator. Hence the light does not come on. Either way, if it does turn out to be the alternator, charge your battery up before fitting. If the battery is flat, there is a chance the nice new alternator could be damaged.

Something is very wrong. Did a bit of a search and it seems you should have a 14.1v regulator. No way should it reach 16.7v. It sounds like the regulator may be faulty. With regard to the cluster, have you tried the instrument self test? With the ignition off, push down the right hand cluster button. Turn the ignition on and release the button. The speedo usually goes to 80mph and the tacho to 3500rpm. Be fairly quick about releasing the button. Hold it too long and you may change the cluster language. No disrespect to said garage but maybe try a local auto-electricians? They may even come out to the car.

Grounding pin 12 of the OBD port is just the same as grounding the same wire at the alternator. IIRC, you tried that and the light did not come on? Perhaps there was not enough voltage at the time? The diagram above is the same one I posted in my first reply. That file also gives you the location of the components - in the case of the diode V9501, it is supposed to be on the left hand side of the engine compartment below X20. The location of X20 is shown on page 7100-0-01. It might be worth testing the diodes to see if they block voltage in the reverse direction as mentioned above. But if the bulb lights, they are probably fine. The alternator is responsible for grounding the wire at D+. When it starts charging, it will change that terminal to a positive and the light will go out (The diodes are there to stop that voltage going in the wrong direction). I realise that the alternator was checked but it does not appear to be switching correctly

The simple solution would appear to be to T into the tank's mains feed and connect to the pipe going to the loo. Then blank off the outlet from the tank. Of course, the mains to the tank needs to be off and the tank empty

Diodes are just like one way valves. They conduct the voltage in the direction of the arrow but not the other way round. So when you put your meter on them, they give continuity one way but if you reverse the position of the probes, you get a very high ohms reading No, it does not matter which way the bulb is fitted. If the diagram is correct, the ignition warning light, ABS and handbrake lights all get their live from pin 7. So you would expect to find continuity between pin 7 and one side of each bulb holder

Diodes only let voltage pass in the direction of the arrow. So if you put the meter on one way round, you will get continuity. But if you swap the probes round, you should get a reading that is so high it is almost infinity. There is a slight complication in that to test them, they should be out of the circuit. That is fine for the one in the unloader relay as you can take it out. Not sure about the one on the nearside inner wing as I have not seen one. But if the wire is disconnected from the alternator, you should be able to test in the same way. Can't say I am 100% certain about pin 7 because it is a while since I worked on a cluster. But I think I would remember if the diagram were wrong. That pin supplies most of the bulbs in the cluster. So you could pick another one from the diagram and check for a common live. In your test, did you bridge from the warning light socket via the bulb to pin 7? And if so, the live side or the negative side? The ignition warning light should be on when you turn on the ignition. When you start the car and it is charging, the alternator turns the light off.

If the battery has been discharged that many times it may be shot. It may read fine when it has just been charged but it is best to let it stand for a few hours and check if it is still reading 12.6v. Perhaps charge it up and continue testing in the direction of the alternator? There is a diode in the relay and another further down which seems to be only present on the M5. I'd certainly be giving them a close look Apologies if this seems to be a little pedestrian but I am not one for throwing bits at cars

Many thanks. Ordered from the first one

My experience with aftermarket/used PDCs is not good. Recall someone posting the name of an aftermarket supplier they had found to be reliable but cannot find the post. Could someone please remind me? FWIW, looking for part 66216902180 (Black) Thanks

Yes, I meant the battery voltage across its terminals because it struck me that you may be losing power between the battery and the B+ terminals. That is often caused by a failure of a fusible link. But you only have 10.5v to start with. Most battery tables show 10.5V as being zero charge so there is not a lot left in it. Ideally, it should be 12.6v. I would be surprised if you could get the dash bulbs to light with only 9.6v. Will it charge up?

There has to be something wrong with the supply. A battery is deader than a Monty Python parrot at 10.5V. It would be worthwhile testing what the voltage is across the battery and at the B+ terminals. (There is the one where you jump start and another in the e-box)

Yes, I meant the battery light. But rather than take the cluster out, you could just remove the unloader relay K61 and check if you have a voltage at pin 4. Nuts on top of the strut tower are usually a really good ground

Even if there is no bulb in there, the voltage needs to go through the resistor. Power to the bulbs comes in on pin 7 of X16 which should be 26 pin yellow. The sockets usually have the pin numbers stamped in on them. If you can't see the numbers, pick another bulb socket and test for continuity to the one for the charging bulb. If you pick the wrong side (negative), you will just get no circuit or a resistance. I know voltage from the bulb socket/resistor goes via the unloader relay and that may affect the ABS but it is probably best to rule out one thing at once PS. It just occurred to me that when you tested and found no voltage, you were using a good known ground for the black probe weren't you? No disrespect intended