Noticed an interesting phenomenon tonight. Engine started as normal after work and ran just fine, no dimming of the lights or other behavior that would indicate that there was an issue with the charging system, and in fact the light wasn't even on until I shut the car off when I got home.

The charge warning light came on, and wouldn't go out. I checked the manual, and puttered around with accessories for a few minutes, and even started the car a couple times for a few minutes each, and the light would dim when I'd rev it, but turn back on when the engine was off.

Curiously, the last time I shut it down, all the lights were off as normal.

There was no resistance to starting, so there was enough of a charge in there, but I can't say my car's ever done this particular thing before.

Any ideas of what to check first? I was thinking maybe a tug on the belts and checking the connections, but I'm certainly open to ideas.

After a short trip at varying levels of leisure

Charge light is on all the time, but the charge behavior is otherwise normal. Engine runs strong, gauge reads fine with no fluctuations. I'm open to suggestions. My search indicates voltage regulator and grounding are both good places to start.

 

Most likely a failure of the diode(s) inside the alternator. Remove the alternator and take it to a starter-alternator repair shop, if you have one in your town


Cheers
DD

 

Thanks, I've gone ahead and ordered myself an alternator as I'm positive the current unit in the car is the old 65 amp Lucas. Guess I'll be wrenching on my car and not my bike on Friday. Definitely not looking forward to digging it out from under the air pump.

Similar behavior today. Everything works just fine. The charge light just stayed on is all.

 

Yep, the alternator regulator has gone titsup (TU, Tango Uniform).
I've had the same symptom on 2 different types of vehicles, A GM Suburban and a Chrysler LeBaron.
And in both instances it was the alternator. None of the alternators had a replaceable regulator.
Easier to replace the whole thing.
One of them had a bearing that was squealing somewhat.
So, a replacement was a good thing.


On my 94 XJS 2+2 I had to remove the alternator from below the car when it just died.
I could have removed it from the top. But, I didn't have to take as many things
off by going at it from the bottom.
My back also felt better by laying out flat on a creeper rather than bent over
the fender for several hours.
Something almost Zen like laying under the Jag and looking up at the engine pulleys and crankcase.
My wife swears she heard me chanting "Oooommm, Ooooommm" at times while I was under there.


And Identify the make/type of alternator. I had to order mine twice because I did not think that I had a Nippondenso type. Big difference in the mounting brackets apparently.
And make sure your battery is fully charged before connecting it back into the circuit.


The Nippondenso alternator replacement sources all seem to be located in California.
None of my local chain auto parts stores had one at a reasonable price (+$400). Rebuild from eBay California shop, +$175 at the time was my only source.


P O R (Press On Regardless!)

 

Got a 115 amp Bosch-type on its way. The alternator still charges, strangely enough.

I'm just bummed out that I'll be spending my Friday wrenching on my car instead of the bike that I desperately want to ride.

Say, when I'm coming at it from the top I know the smog pulley is one obstacle I'm going to have to get past, but what kind of junk will I have to fight coming from the bottom?