[xj-s] XJS12 1992 Headlights come on any time - run battery down

XJ-S
1

Inheritted this pretty red XJS V-12 convertible over a year ago
storage and was dirty, mouse-eaten convertible top, Stinky gas and
battery stone dead. After installing a new battery, fresh gas,
Brake fluid and an oil change drove it 1000 miles home. Happily,
the car starts and runs great and after some detailing and a new
top looks good too.
The problem is that the new battery died within 3 days but
readily took a recharge. The car repeated that trick a couple of
times until I started disconnecting the battery when I parked it
for more than a day. Charging system checked out OK but there is a
very small mA drain with everything off. Dome/Courtesy lights don’t
work and Fog lights won’t come on. One evening - in the garage I
noticed the headlights were on; the switch was in the Off position
but after turning it ON/Off the headlights cut off. The next day,
showing the car to a friend the headlights came on by themselves
while it was running and that night(past midnight) again in the
garage at home. So now I disconnect the battery most anytime it’s
parked. Any Ideas?from my Step-Father. It had previouly sat for five years in

StickFive
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2

In reply to a message from StickFive sent Sun 20 May 2012:

Almost certainly has to be some bad relays, unles there is mouse
damage to wiring under the hood. On my 1994 there are a bank of
relays on both sides of the engine bay, and they do go bad from
time to time, mostly the aux cooling fan relay.

Dave
Atlanta–
Penfold99
Atlanta, GA, United States
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3

Hi John,

Probably the headlight relay. That is the 3rd relay from the front in
the Left Front Component Panel, located on the left wing/fender under
the bonnet/hood.

If only the headlights (and not the taillights or sidelights) are
coming on, and it happens when the key is in the off position, that is
almost certainly the headlight relay contacts closing on their own. I
would suggest testing by simply removing that relay instead of
disconnecting the battery.

The relay is cheap and easily obtainable. Here are some examples:
http://www.motorcarsltd.com/_search.php?page=1&q=dac7686

You can get a Service Manual, Parts Catalogue and Electrical Guide for
your 92 model from JDHT for ~ $25. While awaiting that order, you can
download an “Electrical Guide” for your 92 model from this site, see
the Headlight wiring in Fig.4, and the Relay and Component Panel
locations in the pages before the wiring circuit figures:
http://www.captainjaguarscathouse.com/Electrical_Reference.htm

George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: StickFive johnomay@msn.com

One evening - in the garage I
noticed the headlights were on; the switch was in the Off position
but after turning it ON/Off the headlights cut off. The next day,
showing the car to a friend the headlights came on by themselves
while it was running and that night(past midnight) again in the
garage at home.

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4

In reply to a message from George Balthrop sent Sun 20 May 2012:

Just a way out guess. My 94 jeep has two interesting light
circuits. One is a delay in turning them off with the igntion off
after driving with them on. thje other turns them on if it gets
darkish, dusk, dark cloudy day, underass, etc. It doesn’t always
get that one right. Mut be a light sensor on the wind screen.

Point being, if the Jaguar is so equipped, one of those circuits
may be daffy.

Carl–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
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