Hi I’m new here and am so impressed with the knowledge base here. I would be grateful for some sage advice. I have a beautiful 1976 XJ12 Coupe with a LS swap motor and trans. The car was saved from an engine fire some years ago. Here’s the mystery. When I hook up the battery, the left side (front and back) parking lights come on and at twice their normal brightness. The only way to get them off is to remove the #3 fuse which is weird since parking lights don’t run through the #3 fuse. My windshield wipers and electric windows are also not functioning. All fuses are good. Disconnecting the flasher relay does nothing. Another interesting twist. The turn signals and hazard flashers do not work with the #3 fuse in but work normally when it’s removed. Bout to go nuts pulling my hair out. Any thoughts? Could it be a bad ignition protection relay?
Welcome John,
no need to apologize for the lump!
And yet, it might be the clue to your problem. Where do you start from? Did the lights function properly with the lump at some point of time? If not, the person who did the lump would be the one I’d ask and not allow to leave before he fixes everything.
Apart from that: get yourself the original SII wiring scheme - a pic has been posted before - and check whether your electrics are original. If they are not, try to restore them and fix what is broken from this state. I don’t envy you!
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Welcome, John. You say that the left parking lamps are at twice normal brightness. I assume you mean those at front and rear, and not the side marker lights? Anyway, unless different bulbs and circuitry have been fitted, it’s impossible AFAIK to have a 12V bulb operate brighter than normal unless there is a >12V voltage source available. Could the lights you see be the left front and rear turn signal bulbs (filaments)? They are brighter than the parking light filaments. If so, that might explain some of the fuse mystery. Good luck!
Thanks fellas for the great responses. The fire apparently was minor and confined to the engine. I actually have the motor and hope to rebuild one day! All the electrics seem to be original. Correction, I think they are the turn signal bulbs (yellow in the taillight, yellow in the bumper) coming on not the parking lights. What would make the left side come on solid with a battery connection?
Thanks, John
Obviously you have a problem with something that is related to the circuit of the #3 fuse.
Start by checking that you have good earth connections.
Also try disconcerting one by one the elements at the #3 fuse circuit to see if by removing something the problem is fixed.
Most probably you have a short somewhere.
You have a permanent +12v live feed connecting somewhere to the feed line for the left side indicators.
Check the light bulb sockets for starters.
Only way is to trace the cables until you find the problem.
Electrickery…
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Swapping the engine is hardly possible without interfering with the original wiring, John - and the ‘fiddle factor’ may certainly be involved…
That ‘left’ parking lights come on whenever the battery is connected means that their power is not going through the light switch. That the direction indicators does not work implies that relay/emergency switch is not connected to the proper wires. The reaction to the #3 fuse implies that power through it goes to the wrong place - somehow negating the power to the misbehaving circuits…
In short; one or more wires have been crossed - or may have been shorted, and the fire may have damaged may have played a part. The ign protection relay is not directly involved…
And orderly procedure demands a wiring diagram - as Jochen says. This is only a part solution; the wiring diagrams do not show the routing of wires. Which means you need to know in which areas work was done - and Jochen’s further remark on contacting the one doing the work should be contacted…
It’s a mess; rectifying the problem may be very simple - or very complicated. But as a start; have you actually checked, with the battery connected, what actually works normally - and what does not when switches etc are operated? It may give some further clues - with and without the #3 fuse in place.
And an auto electrician may be a best bet - auto electrics is an art form - even when everything works…
Frank
xj6 85 Sov Europe (UK/NZ)
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All your thoughtful responses are so much appreciated. I’ll start checking all the possible culprits. I’ve got Bradley McLean’s amazing wiring book. Seems like it should be something simple. Finding that live battery feed to the LH turn signal bulbs has proven a challenge.
You might want to post in the “Lumps” forum: many there may have dealt with this.
As in “Sparx, where are you, we need your”
Do the wire wiggle. the wires near the offending lamps. Wiggle and see if any change takes place. work away as far as possible with the wiggle. I sense missing insulation and a cross feed.
Decades ago, my 85 F150 4x4 ad an intermmitant engne misss. I fired it up and very carefully wiggled wires under the hood. Bingo, a black wire up front!! A ground. it had a flakey connector, , I fixed it and created a redundant ground along the same path. solved, miss gone, stayed gone…
Carl
Carlb
John,
as Frank wrote: swapping a Jaguar 12 cylinder for an LS V8 without “adapting” the wiring loom seems very unlikely. In your case there is the added uncertainty of an engine fire - I doubt there could be a serious fire under that hood without serious collateral damage to the wiring loom. So I bet your electrical connections have been messed up big time …
To get you a first picture I include the wiring pattern for 6 cylinder SII sedans. Don’t be overly concerned by the header “XJ6L” - everything should be pretty much the same for coupés. However, you should try to find a pattern for federal 12 cylinder cars. Yet, anything is better than nothing at all …
I understand now that it’s not the side markers nor the parking lights that are acting up, but the indicators. As you describe it someone has connected the indicators with permanent power via fuse #3.
On my car fuse #3 is for the map and interior light, the cigar lighter, the electric aerial and the clock - obviously all powered without ignition on. Brown wire goes in, purple wires go out; one wire is brown/purple and takes to the aerial motor relay. The indicators should be fed by green/red and green/white wires, coming from the indicator switch. Somewhere upstream, but before the indicator switch the indicator circuit is directly connected with a brown, purple or brown/purple wire.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
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Power to the turn signal bulbs are fed via fuse #5 (brown wire, permanent) and fuse #2 (white/pink, ign ‘on’) through the Hazard warning flasher unit and direction indicator stalk switch - there is no permanent power directly to the bulbs, John. In ‘emergency’ position, the stalk switch is bypassed…
If indeed the turn signals (and ‘emergency’) work normally with #3 fuse removed - and your lighs otherwise works normally; your car can at least be driven safely while you are musing on the problem…
Some stray thoughts. Where a two-filament bulb is fitted; with an internal short in the bulb both filaments may light up - doubling the light output. Such a short will do funny things with electrics…
Check if you have such a set-up on the ‘left’, front and rear - and change the bulb(s)…
Frank
xj6 85 Sov Europe (UK/NZ)
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One filament bulbs have one lead contact point on the bottom.
Two filament bulbs have two contact points side by side and close!!
Power to both contacts will indeed by a brighter light!! On a two filament bulb.
Has the lead deformed to join the contact points?? Odd, but who knows…
More likely the socket is shorted across inside…
Carl
Can’t tell you how grateful I am for your great comments on this mystery. I’m new to the hobby with young kids. I just replaced the hazard switch, no change but it needed swapping out anyway. Done lots of wiggling, no change. Disconnected everything with a battery feed coming through the #3 fuse, no change. I’m working through all your suggestions. Another data point that may be a clue. The right turn signal indicator in the speedo lights up even though it’s the left side bulbs that come on with battery connection. Any thoughts? Time to pour another whiskey.
John
Disconnect everything you can related to the turn signals, stalk switch, hazard switch, and see what happens.
Get your multi meter along with the wiring diagram and start from the end, i.e. to the light that turns on by itself, and start going upstream, checking voltage on the way, everything disconnected.
As you can see in the diagram there are two diodes in series with the indicators in the speedo, unfortunately buried somewhere inside the loom, and when they fail and weird things happen.
Something will give you a clue as to where the problem is.
Very nice car by the way!
Good luck.
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This is the way the set-up works, John; with power to the ‘left’ indicator - the ‘right’ dash indicator lamp is also powered - and grounded through the unused ‘right’ bulbs. The problem is the same; constant power to the 'left indicator lamps…
In addition; with constant power to the ‘left’ indicator lamps, this will interfere with the operation of the indicator relay. Which is why the indicators work normally with the #3 fuse removed - it wrongly(!) powers the ‘left’ indicator lamps constantly.
#3 fuse relates to the interior lights - have you checked if you have those lights with or without the #3 in place? It may clarify if that fuse is properly connected - brown ‘in’ and only purple ‘out’. If so; the ‘crosswiring’ powering ‘left’ indicators is downstream in the wiring harness…
Further; the windscreen wipers are powered via the ignition protection relay - as is the heated rear screen. So if both are missing…
Adding also that the ‘left’ park lamps are fused by #8 fuse - but only powered from the light switch. And should be lit with the light switch ‘on’, but not ‘off’…
Frank
xj6 85 Sov Europe (UK/NZ)
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Indeed, Carl but I don’t know if S2 V12 used two filament bulbs…
I’m sort of aware to the vagaries of such bulbs. Looong time ago I spent 3 days searching, in vain, for an elusive indicator fault on my Renault Gordini. Finally took the car to an auto electrician. He looked for half a minute - then changed the indicator/park light bulb; trouble fixed. No charge, but he smiled knowingly…
Frank
xj6 85 Sov Europe (UK/NZ)
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Thank you guys. I may have found a possible culprit. The speedo is a Series III electronic model. when I pulled it to inspect it appears to be missing it’s diode. Could this possibly be the problem?
The missing diode is not the cause, John - the problem is constant power through the #3 fuse to the ‘left’ direction indicator bulbs. You say the indicators (including the speedo and tacho repeaters?) are working normally with the #3 fuse removed - then the missing diode is immaterial. And does the hazard position work - with or without the #3 fuse?
The #3 fuse nominally serves the map, interior, puddle lights, the radio and the clock - do they work with the #3 fuse removed? What wire colours are connected to that fuse?
Have you accessed the ‘left’ indicator bulbs to see the possible reason for the high intensity?
Frank
xj6 85 Sov Europe (UK/NZ)
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