Weird electrical problem - C4 GP mk1

[Hagrid]

The lights dimming was the window trying to go down when it was already down.

In other words, the winder motor was trying to turn but unable to - as I said.

Now you mention it, my window controls also do strange things. Therefore, in short, this is probably not the cause of your issues, just an unrelated one.

I would very much doubt it being a software issue because thousands of cars have the same basic program installed in them, so if the software was that dodgy it would have been fixed long ago.

Or could it just be a software glitch (I've heard some alternators are software controlled) and is that glitch just a glitch or is it caused by another fault.

Much more likely, in fact this is what I would suspect. Vehicle systems are in general too clever for their own good and quite prone to wobblies when they get unexpected signals input.

An example: I drive Volvo articulated trucks; they are known for being rather delicate when their trailer leads are plugged into trailers: some types of trailer lose all their running lights down one side or the other when plugged in and the only cure is to turn off all electrics including interior lights and hazards and then kill the main isolator and wait 30 seconds before trying again. Only yesterday I was riding with a driver who's only had his licence a couple of months, and one of the hooking up 'errors' he did (which aren't errors unless you know Volvos) was to plug the trailer leads in while the ignition was on. That caused about half a dozen different major fault warnings to appear and disappear on the dash, leaving just "emergency brake unavailable" still lit up. The poor driver hadn't got a clue and wanted to book a defect for our engineers to fix. I got him to disconnect and reconnect all the leads with the ignition off, which resulted in no fault warnings at all.

I tend to think that whatever your fog light issue actually is, it seems to be the major drain on your elecs, most likely confusing your car's brain, which in turn is throwing random wobblies. Sorry I couldn't help with the fuse, but I would try to fix the fog light first of all. Have you tried a basic multimeter test of its bulb holder contacts to start with?

[Hagrid]

Marc, if I may, I see MisterFixit put his VIN into his first post. If you can access the car's wiring diagram for the OSR fog light, does it include a fuse and is that fuse labelled or located in a helpful way?

[MixerFistit]

A quick update,

I probably shouldve done this sooner but anyways:

I put a voltmeter on the battery + and engine block and get 14.6V even though my scanner shows 13.8v

When I disengage the voltage drops to 12.6 as read by the multimeter.

I took the aux belt off and repeated the test. There is very little difference between min/max. 12.6 with EPB on, 12.3 was the minimum reading and that's with blowers to full and headlights and brake lights on for over a minute . I also didnt notice much change in speed on the blower (maybe it was already slower due to no alternator at all)

So could it be the alternator's regulator? But why does the handbrake affect it if so?

As for the RH rear fog lamp, I switched it off in lexia and the fault immediately jumped to the LH rear fog lamp
I've turned them both off now, behaviour the same but my laptop battery was getting low so I'm charging it back up before I do another scan. I'm guessing these don't have fuses because the BSI monitors them and can cut an overcurrent itself