Charging light on 87 XJS V12 Coupe

XJ-S
1

I have recently developed a problem with the charging light on my 1987 XJS V12 Coupe, when I start the car up the voltage goes from 12 volts to 13.8 volts immediately but the charging light stays on then slowly dims and goes out after 20- 30 seconds, I am wondering where the problem lies, is it in the regulator built in the alternator or another circuit somewhere else in the car? TIA Geoff

2

Hi Geoffrey,
This is normal, there is no problem in my humble opinion.
Cheers Bruce

3

I agree with Bruce. Mine does the same thing. Not a problem.

4

Mine did the same.

But…

Mine was an '88. It had two charging system lights. One was a typical ignition/charging light (with a battery icon as I recall). It extinguished quickly. The other was an overcharge warning light (with a lightning bolt icon) which extinguished slowly. I think your '87 would be the same.

Something like that. It was 20 years ago so my memory isn’t 100% clear.

Cheers
DD

5

Mine has both the ignition light (with a battery icon) and an overcharge light (with the flash icon) the overcharge light goes out immediately but the ignition light takes awhile, I never remembering it doing that before, but as the battery is charging I guess I have nothing to worry about but wonder why things changed (oh I know, it’s an XJS!) My 91 convertible does not do this it goes out immediately.

6

My 1988 does the same, but usually goes out after just 8 seconds max.

I wonder if it takes longer to go off if the battery is less charged up? If so, do you have a drain on battery like light left on?

7

Greg, that’s a great point, I don’t have a drain on the battery but I do drive it a lot of very short trips, I am going to charge the battery tomorrow and see if that changes anything, cheers Geoff BTW my 91 has a brand new 115 amp Bosch alternator, not sure what is in my 87 Coupe.

8

Greg, charged battery up no difference, I did actually time it took to extinguish and it was about 10 seconds not what I thought, also I have noticed it flickers while dimming it’s not a happy light.

9

Geoffrey,
Hi, once again i think this is normal. Seem to remember it being mentioned in the hand book.

10

Totally normal. Mine does the exact same thing. British.