XJ6 & XJ12 Series I, II & III 1968-1992

Lucas Gremlins, STOP LAMPS

 
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Old 11-29-2008, 09:27 AM
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Default Lucas Gremlins, STOP LAMPS

My '87 XJ6 all of a sudden has no brake lamps. All bulbs check good, fuse has power on both ends and a good fuse. I'm good with wiring, but the schematic in the Haynes book I have blows. I checked the wires at the brake pedal switch and both leadsshow they are grounded, when disconnected from the switch. The switchOPENS/CLOSES properly. Injecting a 12VDC pulse into either STOP lamp switch lead (still disconnected) pops the breaker in the test lamp. Haynes wiring diagram shows the brake lamp power goes through a (STOPLAMP FAILURE SENSOR), however, no failure lamp is shown on the dash. The park brake lamp works. The cruise control never did.
What's goofing me up, is how can there be a GND on both STOP lamp switch leads without frying the fuse?

-Where is the 'STOP LAMP FAILURE SENSOR'?
-Does STOP lamp power go through any other switching/module before going back to the lamps?
(I ask that one, because the leads on the STOP switch are yellow with a white stripe and the diagram says they should be GRN. Bear in mind nothing was worked on, change, replace, wiggled or modified in any way before the transition of working to NOT working STOP lamps.)
-What could have happened that is simple? It worked one minute and dead the next?

Also, shorting the brake pedal switch leads together does NOT change the failure.


Thanks for any assistance or ideas.
 
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Old 11-29-2008, 10:36 AM
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Default RE: Lucas Gremlins, STOP LAMPS

hi,

cursing Lucas will only bring you bad luck, so if I were you, I would erase your cursing from your post. Bad Karma.:-))

I own two old Jaguars and the electrical systems in these cars arestable and congruent, which is a lot more than can be said for a 2007 Chevy,Chrysler, or Ford. If you want to talk about stinking electricals, then ask my brother-in-law about his 2007 Malibu, and his 1999 Jeep Cherokee.

Here's my suggestions:

1) buy the Factory Service and Parts Manual in CD. Haynes manuals are a joke! You'll never get anything done with a Haynes. Go to any Jaguar Dealer or order the real thing at any of the following sites for less than a tankfull of gas:

http://www.lbcarco.com

http://www.jaggraveyard.com

http://www.jdht.com


2) the Bulb Failure Sensors are located in the trunk, behind the upholstery panel held by two black plastic screws with large black washers. The panel is mounted Left to Right, sameorientation as the rear seat back. It could be something as simple as wiggling the wires on each sensorto make sure they are making good contact, so be gentlewith the wiring and don't go there in a fit of anger. It never works. Take a deep breath amigo and think "easy does it". Jags do not like rough.

3) if the Cruise does not work, there are 3 possibilities:

a) the rubber accordion located in the engine compartment is cracked, if inspect it carefully and find any cracks in the rubber, use Silicone Sealant to seal the cracks from both sides.

b) the Neutral Safety Switch located in front of the Shifter is mis-adjusted, (a typical problem).

c) the black ground wire located in the Turn Signal Stalk Switch lost contact with the SET switch located at the end of the Stalk Switch. Rare but it happens.

All the above are repairable without buying ANY parts, just takes knowledge and patience.
I know of no other electrical-component manufacturer who makes repairable components, certainly not BOSCH, certainly not DELCO. Only Lucas componentscan bedisassembledand rebuilt.

d) The pedal Brake Switch is known to fail INTERNALLY, there's a plastic piece that breaks inside after 20 years of service. Many of us have opened them up and repaired them.The Second Brake Pedal Switch has nothing to do with the Stop Lights, it is the Cruise Control's OFF switch, when you are on Cruise and step on the brake pedal, the Cruise is turned off.

e) remove the tail lamp's plastic lenses, then remove the tail lamp Housings; (note the screws are not Phillips but POSI-DRIVE, and although phillips will work, it will eventually round the heads),Wiggle and pressthe rubber plugs together to make sure there's good contact.

Overall, I do not think the Bulb Failure Sensors will prevent the Stop Lights from working, in any case you would have a WARNING LIGHT come ON at the dash telling you of Failed Bulbs, that's all the Sensorsdo.

My guess is the Brake Pedal Switch, or if you have been working in the car lately, retrace your steps to see if you left something disconnected.

I will try to find the instructions for rebuilding the Brake Pedal Switch if you want them. Or if you prefer to buy a new one, I can post a few sites that sell them.

Jose
 
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Old 11-29-2008, 11:24 AM
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Default RE: Lucas Gremlins, STOP LAMPS

good that you edited the cursing of Lucas out of your post.

Jose
 
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Old 11-29-2008, 11:52 AM
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Default RE: Lucas Gremlins, STOP LAMPS

I also added that the switch works and shorting the wires does nothing. Also, I found in testing the brake pedal switch, the circuit seems to be closed when the pedal is UP and OPEN when the pedal is engaged. Is this correct?
 
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Old 11-29-2008, 12:33 PM
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Default RE: Lucas Gremlins, STOP LAMPS

I do not know the answer to the Switch's open or closed default mode.

look at the attached picture of the trunk's electricals. You are looking for component Number 9.

Also, under the ECU, (Engine Computer), there are two or three fused wires, one is for
the Brake Lights. Check those fuses.

If you say thatthe lightswere fine and all of a sudden, no brake lights, it is definitely a Fuse.
I would go back and check/replace the Fuses one by one, sometimes they look fine and are not.

Legend to the picture:

1 Motor/Solenoid, trunk lid locking
2 ECU, fuel injection
3 Sending unit, fuel level
4 Fuel pump
5 Motor, antenna
6 Relay, antenna
7 Bulb failure unit, rear lamp
8 Bulb failure unit, rear lamp
9 Bulb failure unit, brake lamps
10 Motor, power sunroof
 
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Old 11-29-2008, 12:38 PM
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Default RE: Lucas Gremlins, STOP LAMPS

[:@]
I've been in the trunk. Everything looks brand new there, no change after wiggling.

The car is in great shape with less than a 100k on it. It's got regular scheduled maintenance from the original, local dealer. Everything works except the cruise control. Neutral safety switch works properly (allows START in P or N, but no other gears) I have not been working on the car, but I was lightly rear, ended recently. But like I said, the brake lamps (all three) worked fine before I drove out for Turnkey dinner and when I got back, nothing.

Again, why is the pedal switch a CLOSED circuit when at rest?

 
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Old 11-29-2008, 12:49 PM
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Default RE: Lucas Gremlins, STOP LAMPS

The XJ-6 Neutral Safety Switch hastwo adjustments,the Cruise Control will only work in the "D"shifter position, so an adjustment is necessary just for it. The Shop Manual has the procedure. I posted it here not long ago, do a search for Cruise Control.

If you think the switch should be OPEN instead of CLOSED when at rest, you have a short somewhere, obvious place to look is in the rear-ended areas.

Did you check the Fused wire located under/near the ECU ?
 
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Old 11-29-2008, 12:56 PM
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Default RE: Lucas Gremlins, STOP LAMPS

It seems the pedal switch changes state, whichever... whatever.

In regards to the brake lamps circuit in general, is there a relay between the lamps and the power source (as opposed to American cars who run the power for the brake lamps right through the pedal switch, then through the hazard relay.) Obviously the hazards are working, in the Jags, I can see that that is a separate circuit.

-Where is the ECU and what color is the fused/lead?
 
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Old 11-29-2008, 01:11 PM
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Default RE: Lucas Gremlins, STOP LAMPS

try to follow the rear Glass-mounted Third Stop Lamp wiring, see if it gets to a Relay, I am not 100% on the 1987, but I think it does have a Relay. If so, I bet you can open the relay case and check the contact points for rust.

The fused wires are Red in mine.

The ECU is the large aluminum case located in the trunk, to the right of the Bulb Sensors, same area.Large rubber plug connected to it, looks like a Serial Cable Printer connector. Look under it, look under the carpet, for 2 or 3 loose and fused Red wires.

I would suggest replacing the Brake Pedal Switch, substitution is the way to eliminate it as the problem.
 
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Old 11-29-2008, 01:17 PM
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Default RE: Lucas Gremlins, STOP LAMPS

ECU found in truck, duh.

-FOUND: 3, 3Amp inline fuses. All test good.
 
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Old 11-29-2008, 03:20 PM
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Default RE: Lucas Gremlins, STOP LAMPS

Bloody right, there.

Must have moved the angle of the switch with me size 13 boots. Simple adjustment solved the problem. But I do need a new switch.

Thanks for the help John.
 
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Old 11-29-2008, 03:41 PM
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Default RE: Lucas Gremlins, STOP LAMPS

Moral of the story is:

#1 Listen to those who've done this all a hundred times before you tear open every panel onyour car.
#2 If you wear size 12 boots or larger, mind the bloody switches.
#3 Never bad-mouth Saint Lucas, he's not partial to it.
#4 Also, when troubleshooting a Series 3, the ignition has to be in position 1 or 2 to light the brake lamps.
(If the ignition is OFF, no juicey juice!)

All in all, it was a lot more simple than it had to be. If I'd have just loosened the switch and moved it a bit, I'd have solved the problem 4 hours ago.

 
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Old 11-30-2008, 09:01 AM
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Default RE: Lucas Gremlins, STOP LAMPS

replace the corresponding fuse in thedriver's side fuse box. Under the premise that this happened instantly, no warning, working fine one minute, but not the other, it must be a fuse.

...unless the 3rd Center-Mounted Stop Lamp has blown bulbs and stops the Stop lights from turning on... I would check the bulbs, 5 of them.

The 3rd Stop Lamp plastic cover has two "buttons" underneath, press them up as you pull the cover off, then you see each removable bulb socket.
 
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Old 11-30-2008, 09:40 AM
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Default RE: Lucas Gremlins, STOP LAMPS

Joseph Lucas was not a saint. He was an electrical engineer. His last days were spent in a villa in Spain where he changed his name to Jose.



 
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Old 11-30-2008, 09:42 AM
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Old 11-30-2008, 06:18 PM
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Default RE: Lucas Gremlins, STOP LAMPS

Wow, that's great story. They don't offer Sainthoods to electrical Engineers? Pity that.
How about a Knighting?

Well, now we know why you have such good answers.

Say, know how to get exhaust parts?
 
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Old 11-30-2008, 07:20 PM
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Default RE: Lucas Gremlins, STOP LAMPS

No Knighthood either, I'm sorry to say, though he deserves it.

My answers are from owning my '84 for the last 17 years + this year. You would expect I would have learned something in 18 years.

Exhaust: I ordered a Euro-style Y pipe, (catless), same as that used in the Series 2, from Motorcars Ltd.in Texas.One less cat to fry. I sent it, the transmission clamp,and the two over-the-axle pipes to Jet-Hot Coatings where they coated them in and out with their Sterling coating. No more hot spot under the driver'sfloor.YEEHAWW.Sterling coating works, it lowers the exhaust temperatures.

I foundnew-old-stock rear resonators and mufflers from a Jaguar supplier in Michigan and that's how I rebuilt my exhaust system. I also used stainless steel Band clamps from a racing outfit in California. ( U clamps distort and crimp the pipes, causing damage, I don't use them, and Jaguar exhausts are never welded, so clamping needs to be goodand exhaust adhesive needs to be used too ). I did it myself, placing the car high on blocks, part by part, everything perfectly aligned and polished like chrome!!.

The Front cat was opened and cleaned up by a Jag tech, rewelded and pressure tested and then I reinstalled it. Two less cats to fry. The car passes inspection w/o.Responds a lot faster too.

You might check with Ken at Motorcars Ltd. to see if he still has the Series 2 Y pipe, and the original Series 3 mufflers and resonators,two of each. If you want stainless Band Clamps, let me know. The adhesive you can get at Advance Auto Parts or AutoZone.

what Pinninfarina Princess are you talking about? How about a pic?
 
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Old 11-30-2008, 07:24 PM
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Default RE: Lucas Gremlins, STOP LAMPS

here's a pic of the Series 2 Y pipe and transmission clamp for the Y pipe.

(click on ATTACHMENT below).
 
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Old 11-30-2008, 07:29 PM
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Default RE: Lucas Gremlins, STOP LAMPS

here's my car again on blocks about 3 months after installing the complete new exhaust, raised to check tightness of all bolts and nuts, allwhich I replaced in stainless steel including washers. This was in 2000.

 
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Old 11-30-2008, 07:39 PM
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Default RE: Lucas Gremlins, STOP LAMPS

checkthis one:

this is the stainless steel exhaust system I installed in my 1965 S type. This one came from England, made by BELL Silencers UK, ordered from SNG Barrat's in the US.Show quality, everything polished like a mirror. Same thing as the XJ, I raised the car on blocks, and went from front to rear, part by part, using stainless Band clamps and exhaust adhesive. Bell makes a complete system for the XJ too.
 

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