XJ12 III Electrical Hook-up Queries

1987 Cdn XJ12
I’m in the process of re-connecting the wiring after a simple engine bay clean up turned into… well you know.
2 queries.
There is a brown/black wire that comes off the alternator and back through the engine V with a female spade connector just behind the throttle pedestal. Where does that connector connect to? The wiring diagram seems to indicate an ignition warning light (I thought I had taken lots of pictures??)
Second, there is a harness (DAC4549 right front harness) with 3 terminals on the end; one is a ground that would fit over a bolt, one is pink/orange with a female spade, third has 2 pink/orange wires into a female spade.
Been over the wiring diagrams with just a headache to show for it!
Thanks guys
Dave

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That’s where the brown/black goes to, Dave - you just have to find the corresponding male connector…

DAC 4549 does not ring a bell - which would then help. But, like the first case, with with a loose connector - finding a corresponding place to put it is a reasonable progress…?

In both cases; there is a vacancy somewhere, probably within reach - which is weak advice…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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I can’t find…so far…any pink/orange wires in my various diagrams. I’m using USA-market XJS diagrams which are usually relevant to Series III V12s… but one never knows where the odd exception will pop up.

Still, your dilemma sounds familiar. I have a vague recollection of the same or similar wires causing me confusion when I did my V12 conversion. I’m pretty sure they went to the extra air valve (in the RH air cleaner housing) and the vacuum solenoid valve (rear of RH inlet manifold). At some point they connected to a larger harness in the vicinity of the balance tube at the rear of the engine.

Sorry I can’t offer anything even remotely certain.

Cheers
DD

you are right Frank, the other end has to be there it must be tucked somewhere that I can’t see.
Thanks

Thanks Doug
I don’t have all the pieces back together so the answer will probably appear.
Regards
Dave

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There is another possible explanation, Dave…

Jaguar usually wired every model year the same, irrespective of market and equipment level. Where Items were not fitted, the respective wires were left unconnected…

My manual does not show the electrically operated supplementary air valve on the US description - though Doug mention its presence on his. Shown on my description with one ring/bolt and a pin (male) and socket (female) connector…

Further; the ‘European’ set-up used an electrically operated changeover valve for distributor vacuum supply; two pin connectors. Not used on US versions - which used a vacuum advance dump valve for this purpose

Comments; Jaguar continuously ‘upgraded’ equipment levels regardless of market and model year - but they were very sloppy in updating wiring diagrams. So wiring diagrams cannot be completely relied on for individual cars. As Doug also says; ‘one never knows where odd exceptions will pop up’! Furthermore, they may indeed have started using spade connectors - the pin and socket connectors were/are not really reliable. And indeed; there is the PO issues - some changed to spades…here and there…:slight_smile:

However; the brown/black from the alternator definitely goes to the battery/ign warning light. And the corresponding connector may have slipped inside the cabin…?

As for the others; the best may simply be to forget them - and observe, with the assembling finished, what actually doesn’t work. If it eventuates…:slight_smile:

Like Doug; ‘…I can’t offer anything even remotely certain’ - and I’m not sure any mortal can…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

1 Like

Hi Frank, thanks for the follow-up.
I think I may have the harness mystery solved, the same color wiring comes off the horn relay.
the horns are off the car so it wasn’t apparent that there was a solution there.
On the brown/black I crawled up to get a good look and could not find a corresponding wire.
Could it connect to a relay?
Dave

Horn wiring typically has lots of purples, Dave. Not oranges or pinks.

As for the brown/black, could it possibly be black/brown? It would make a difference.

Cheers
DD

Hi Doug
My wife tells me that colors are not my strength so it could be purples.
I’ll check on the color combo.
Dave

Hi Doug
The best I can make out is the wire is equal parts brown and black.
Also, I checked the horns and the form the wires are holding support that the harness is for the horns.
So DAC 4549 is the horn harness.
One down, one outstanding and a new one!
DAC 7721 comes off the vacuum dump valve and ends with two 3 wire bullet and barrel connectors.
Both have wires that are black, yellow, yellow with black bits.
Can’t figure out where this one goes??
Cheers
Dave

correction: it comes off the solenoid valve

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No relay, Dave, it connects directly to battery warning light - it is the light’s ground connection.

The light is powered from ign switch with ign ‘on’. With the engine not running, the light is grounded through the stationary alternator - lighting up. When the alternator spins, producing power, voltage from alternator matches voltage from battery - and with equal voltage on both connections, no light…

I assume the wire is not long enough to reach the warning light cluster - for a direct connection? Alternative; the lose wire goes to one of the multipin connectors in the engine compartment - and from there to the warning lamp cluster…?

Frank
xj6 85 Sov Europe (UK/NZ)

Hi Frank, thanks for the great explanation, that helps understand things.
The wire is not long enough to reach the cluster and I can’t see any passage way in the firewall either.
The next thing I am going to look into is the multi-pin option that you mention.
Dave

So I un screwed/bolted as much as I could on the firewall within reach of the orphan connector and the only open connection is a male spade on the starter relay (the wire is a female).
Lots of wiring coming into and out of the relay, into harnesses that disappear some into the firewall.
Frank, I know you described no relay in the circuit but is it possible that the connection to the warning light comes through the starter relay?
Thanks
Dave

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Negative, Dave - the brown/black wire from the alternator goes directly to the ‘batt’ lamp. The bulb is powered from the ign switch, and grounded through the stationary alternator. With the alternator running; the lamp gets 12V on both sides - extinguishing the light…

You may try removing the warning light cluster - to possibly trace the relevant wire from the cabins side…?

Frank
xj6 85 Sov Europe (UK/NZ)

Thanks Frank, looks like a case of mission creep but I need to track it down.