I have a 1987 XJ6. Recently the ‘Battery’ light came on on the dash and stays on. Usually would indicate a faulty charging system, but I checked, and I am getting 13.9 -14.0 volts at the battery when running, and the voltmeter on the dash indicate charging also, so that’s not the issue. I believe it is the Lucas 3AW Warning Lamp control unit that may have gone bad. My manual just says it is located in the engine compartment adjacent to the output control unit 4TR, but I can’t seem to locate either item! Can anyone tell me (or send a picture) of where these are actually located?
Peter,
What kind of manual are you using? I have owned and worked on my Series III XJ6s for 18 years now and they do not have a 4TR. I think the Series I XJ6s might have had them, but not the Series III XJ6s.
I believe that your Ignition warning light might be caused by a broken or disconnected wire. Did anyone work on your car, particularly around the alternator, just before the light started coming on? There is a Brown-Black wire that should go between the alternator and the warning light. I think that if that wire is disconnected or broken then the Ignition warning light will illuminate even if the alternator and battery are OK. I am not certain of that but I seem to recall someone having that problem a while ago. Perhaps if you searched the archives for “Ignition warning light” you might find some helpful posts.
Paul
Paul is right, as usual, by suggesting that you check wiring (always the best place to start) and in advising you that your '87 doesn’t have the control units you mention.
My suspicion, however, is that your alternator has a faulty diode.
Cheers
DD
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There are no ‘warning lamp control unit’, Peter - just a wire (white) from the ign switch to the lamp, and from the lamp to the alternator connection (black/brown) wire…
As other say; the usual fault is the black/brown wire disconnected/broken, and grounded…
Frank
xj6 85 Sov Europe (UK/NZ)
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Thanks all for the suggestions. I’l check the wiring, no work has been done lately, light just came on the other night while the wife and I were out. I have the Haynes manual, not the first time it’s been wrong! I have a feeling it is the diode, I had the same issue on my MGB GT - ended up just taping over the warning light since I didn’t want to replace the alternator just for the diode!