Charging light short not turning on ( warning light problem )

Hey Guys!!! Happy New Year!!!

Need some help,

I was replacing the instrument panel lights on my 87 jaguar xj6 series 3 and when charging the indicator warning lights, I accidentally shorted out the back of the indicator warning light unit to ground. ( it was a small spark,I forgot that I had the ignition key on ) :grimacing:
Now, its not charging and the battery light and the hand brake light don’t come on. The hazard, high beam light do come on but non of the rest don’t. Please note before I touched it, the only lights that worked were the high beam,hazard, hand break and the battery light, not sure the other lights on that warning light panel were working.

Do these cars have a fuse for that, if yes where ?
Do this car have an external or internal alternator regulator, if external where?

Thank you for your time.
Blessings

Not sure what exactly is at fault here. I’m just three sips into my first cuppa coffee. But, for starters…

Battery, oil pressure, brake, handbrake, low coolant, and seat belt warning lights are not fused. All have 12v “+” with the key on and are individually grounded to operate.

The battery light socket has a small resistor wired in parallel, which you may have noticed

Internal regulator.

Cheers
DD

Hi Luis,
google for a pdf of the S57 wiring guide, at least you will find detailed wiring diagrams to see fuses and wire colours so always useful. I never looked at alternators so much so I don’t know if it’s fried somewhere or if there’s some simpler explanation.

David

Luis, the warning light cluster simply screws in place and, as I recall, there’s enough slack in the wires to pull it outward enough to visually inspect the backside. Maybe something will present itself?

Cheers
DD

No charge in actuality from the alternator? Or merely, a lack of an indicator. Odd,

The charge light is an exciter to “urge” the alternator to charge. Sans it, rev the engine and it should self excite.

Use the VOM to verify charge or lack thereof from the alternator.

Ditto on getting the S57 publication. Best i have seen. helped a lot and taught me a lot.

Enjoy that car and welcome aboard.

Carl

Thank you!! Good Morning!!

Thank you Mr. Dwyer, Mr. Hutchins and Jauch for the clarification and different explanations.

sorry I just responded, just got back home.
WOW,
I amazed that you guys answered so fast!!!
I thought it would a couple of days for a response. Bless you guys!!!

Mr. Dwerer yes the batt light has a resistor, and yes it has a lot of slack to pull it out. But when I was going to reinstall it I forgot to turn the ignition key off… Rookie mistake :pensive:

I checked thin wire behind the alternator and no voltage in going to the alternator (excite wire) …
No 12v + power coming to any other warning lights. Only ones that are working are the high beam and the hazard light when activated.

So I followed Mr. Hutchins advice and rev the engine and it did self excite !!!
All the warning lights started working again!! ( I triggered them one by one )

But when I turn the engine off and restart it no charge from the alternator and no warning lamps work…
I rev it and everything comes back to normal…

I discovered that another way that it works is that when I start the engine, and I jump 12v + to the positive side of the batt warning light… and presto… it works…

So it seems that I need to find where there is an open circuit between the warning lamp and Im guessing the ignition switch… Can it be the diode or resister on the back of the warning light panel?

I attached a picture for better clarity… will keep poking at it and download that pdf of the S57 wiring guide…

Thank you all for your support, you shined a light and there is hope… I had already bought the alternator and the an external regulator as per Autozone specs …

Let me know if you have any other awesome suggestion.

Thank you

Have a Blessed day guys!

20210103_211232|375x500

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Clarify, Luis…

‘Normal’ means that warning lights are ‘off’ with the engine running, except brakes and seat belts, which are separately controlled by relevant switches. With no voltage on the white wire from the ign switch; the warning cluster may get voltage from the running alternator…?

‘Batt’ light is powered, 12V, from the battery via the ign switch (ign ‘on’) - and grounded in the alternator light ‘on’. As the alternator starts charging it produces 12V - countering the 12V from the ign switch. With equal voltage on both sides of the bulb - the light is ‘off’.

The problem is lack of power from the ign switch - faulty wire or ign switch. This should really be irrelevant to shorting the indicator light - but the nature of the ‘fiddle factor’ is unpredictable. However, does the indicators, and those warning light work? You may have blown a fuse there?

In any case; find out where the power from the ign switch (white wire) is lost…

And incidentally; working with electric parts; the battery should be disconnected. Which we usually omit - usually without penalties…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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Than you Mr. Andersen

OK what I refer to as Normal is that all indicator and warning lights work when the alternator kicks in. Yes all lights are off when the engine is running, in other words, all indicator/ warning lights work normal when triggered ( hand break, low oil pressure , low break fluid light, low coolant, seat belt, ). So I go to each sensor and ground them and all lights work.

But when I switch car off and restart it without rev. the engine, with alternator is not charging/kicking in.
Non of the warning lights work even if triggered ( hand break, low oil pressure , low break fluid light, low coolant, seat belt )
So like you mention, they only work when they are getting voltage from the alternator once it kicks in.

I agree the white wire from the ignition is my next step I will look into. Yes it was a small

And yes, I typically disconnect the batt when working with electrical, but did it in a hurry and forgot to consider that these car are all metal. Ive gotten too comfortable with modern cars where everything is plastic. :man_facepalming:

Note, only indicator lights that working with or without alternator working are the high beam and the hazard lights. ( low beam indicator was not working originally , will deal with that later. )

Thank you for all your help… will get back with updates

Blessings

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Which means that the ‘batt’ light is never lit, Luis - have you actually checked if the bulb is OK…?:slight_smile:

This has of course no bearing on the other lights not working unless the alternator is delivering power - which again means that there is no power to cluster from the ign key, white wire. One way of verifying that this is the problem is to jumpwire 12V to the white wire terminal on the cluster. If the that restores normal ‘normal’ functions, you have a specific identification of the problem…

Not all alternators require exciting - remanent magnetism in the alt then does the trick without reving up the engine. Which is neither here nor there - yours obviously needs some excitement…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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Good morning Mr. Anderson
Thank you for your response

Yes Batt light is not coming al all and yes light is working… And yes I jumped 12v + to the white wire and everything goes back to normal. So my next thing to check is the ignition key and trace that white wire. I shook the wires behind the ignition switch hoping it was a loose contact but, nothing happened… Fun fun fun!!!

Honestly I seem to enjoy when little things like this break down, its a chance to get to know the car a little better. This sounds crazy but, I can actually visualize a Hollywood like video tracing/running thru the car as I try to figure things like this out.

Thanks again everyone

Will get back with updates

Have a blessed day!!!

You have the right attitude, Luis, bless you - you’ll be all right…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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