Well, here we go: after half a year of (almost) trouble-free driving I encountered my first serious problem today:

while driving home I noticed the voltage gauge showing something around 11 Volts instead of the usual 13/14 Volts. The lights looked slightly dim as well.

Fortunately the battery is pretty new and of a serious size so it took the battering with grace and brought me home. I checked with a voltmeter and the battery reads 11.8 V with the engine running or not. So no charge at all.

Strangely enough there is no warning light on. The car starts normal, no sluggish cranking. Managed to obtain the wiring diagrams and found a fuse in one of the regulator lines (WU) which was intact. No luck there then.

Checked the wiring as much as was possible, went through all the fuse boxes, no luck. All good.

I've removed the battery and giving it a good charge over night, should take me through the day (I drive about 50 miles every day).

The question is, what could it be? The alternator? Wouldn't then the battery symbol light up?

Any ideas anyone? Before I go out and separate from serious hard earned cash for something I could perhaps fix myself?

Suggestions much appreciated.

 

A guess from the colonies.

My 3.2 did similar and I was messing in the boot just prior, so my fault obviously.

On the +ve battery cable is a connector/fuseable link arrangement, and I found it to be slightly loose, like 1 flat of a 6 flat nut. Mmmmm, dissmantled, quite tarnished, cleaned properly, refitted.

Better, not quite right.

Did the same to the -ve terminal and made real sure that bolt was not stripped in the terminal.

That was 4 years ago and still fine.

A decent "sparky" (auto electrician) should be able to test the output of the alternator, at the alternator, very quickly and easily.

I agree with you about the idiot lights, but have no answer.

SECOND thought as i typed all that, bugga.

Is the alternator getting excited????. That is the ignition signal to the "small" wire of the alternator, it should have battery voltage in it with ign ON and engine OFF.

These cars have many IGN relays, usually Blue coloured, and one under the bonnet in the RH fuse block comess to mind.

Some alternators will "self excite" eventually, but I do not know if our Hitachi are of that breed?.

 

Many thanks for your advice! It was indeed a blown fuse, feeding the 'exciter' of the alternator. I managed to get hold of a complete wiring diagram for the X300 and eventually located the fuse: its in the right-hand engine bay fuse-box, the first one in front of the (brown) relay. Nominal value 5 Amps, but when I replaced it, it blew straight away. Tried a 10 Amp and it held out, no smoke or burning cables anywhere (I don't recommend doing that, as there is probably a reason for the 5 Amps). I settled for a 7.5 Amp, which has held since (knock on round wood...) but I recon the alternator will need replacing.

All we need now is some nice weather so I can attend to the sagging headliner...

P.S. my regards to that lovely place in the sun. Nearly settled there in the 80s...

 

I have had a similar charging problem with my 1995. Changed the alternator, went through wiring. I am an EE and have lots of test toys. I measured Voltage on the charging line and found a 2 Volt drop on the stud carrying the alternator current through the firewall right near passenger left knee. I cleaned it and it helped but the problem came back. Finally ordered a replacement copper stud assembly including new nuts. Old nuts were steel new nuts are copper. Problem is fixed now for more than a year. Easy to do if it comes back.