Thanks, Jose, actually read that info from him and did that. Cleared up and returned after each 17.5V restart. Although it is intermittent, I’m not driving again until I fix the problem. Just don’t feel I should be comfortable about 17.5V popping in and out of the electrical system. Luckily, the TC is still operable.

 

Just tossing this out for the heck of it, Here's a pic I took yesterday of an F355 with a dedicated alternator ground




Cheers
DD

 

That is a great idea. That prevents future ground issue’s if the mounting surface’s become “un-shiny”.
I’ll be entering the garage the next couple of day’s to get to the root of these issues.

 

back in the 1990s there was a Jaguar-trained technician who worked at Motorcars Ltd. in Texas who told me to add a separate ground strap under the 1-wire oxygen sensor and the other end to the body.

I did and it made the idling very stable in my 1984 built in 1983.

Then in 1985 or 1986 Jaguar came up with oxygen sensors that had 3 wires, one a separate ground, one a pre-heater ( I think), and the third wire the normal wire to the ECU.

I've never added a separate ground strap to the alternator because this is the first I hear of it. But I plan to do so.

 

Phil Prince?



Yup ! Over the decades that mod has caught on and is used on many other cars as well



Right ! Those were the heated 3-wire O2 sensors. Ground wire, 12v+ wire to the heater, and the signal wire. The 3 wire sensors became virtually standard issue for most all makes in that era. The idea was to heat the sensors so they'd start working more quickly.

There was recall in 1986-ish to retrofit XJ6s with the 3-wire sensors. I can't recall which cars were involved; perhaps only those registered in California? Anyhow, the 3-wire sensors became standard issue for the 1987 model year. Simultaneously the oxygen sensor warning light system was deleted as well, one of the very few changes between 1986 and 1987 cars.

Cheers
DD

 

you remember Phil? great guy. I wonder what happened to him. He used to be at Jag Lovers too.

I thought 1985-86 was the year the 3-wire O2 sensors were introduced, but you say it was 1987?

i sell a ground strap kit in my website for the 1-wire O2 sensors. Nice copper braided, half-inch wide strap, with proper sized ring terminals. I am going to use one for the alternator too. Grounding the O2 sensor in my XJ-6 has been one of the best mods I've ever done to it.

 

Jose, I was JUST about to contact you, I previewed the strap at your site and I can’t for the life of me figure out how to get to the “purchasing page”. Hopefully once the grounding issues are solved, the correct voltage will be applied to the transducer and the odometer unit. This “may” solve the problem of “my speedometer works but my odometer doesn’t”. If not, I’ll send if off to Speedy Cables for repair and get back to DRIVING the car I’ve desired for 40 year’s.

 

Tony, sorry I just saw your message, you can send me a private message here or on the Contact Page in the website, click on the "Click Here" to get my email and contact me. Do you want to ask about the Ground Strap I sell? Do you want it for the O2 Sensor or for the Alternator? . Thanks.

 

I suggest that the ground strap go from the alternator to the spot on the wing wall where the battery ground is secured. assures that grounds of other stuff to either chassis or engine block are connected.

Better would be battery ground to engine block .And any other ground back to the engine block.
AKA no grounds to chassis !!! Impractical, yeah !!

Carl

 

Carl that would be a long distance marathon from the alternator to the battery ground bolted near the wiper motor.

I don't think anybody makes such a giant strap. Maybe one from a bulldozer or army tank.

The ones I have are 21" inches center of bolt to center of bolt and that is quite enough to reach most any point near the alternator or O2 Sensor.

the O2 sensor strap in my car goes from the sensor to one of the bolts for the cruise control bracket with plenty leftover because you don't want it fuly stretched, play in the length is desirable.

 

WOW! Okay! Learned a useful tip today. Went out to the garage, jacked her up, removed the adjustable trunion(?)on the alternator


Could not understand why the schematic’s show 1 brown wire connected to the alternator and terminating at the left bulkhead and I have 2. Studied long......realized I was studying 1987-1988 XJS...I have a 1984 XJ6. FUTURE-remember to properly label ALL downloads. Took all the wind out of my sails. I’ll sail again, first thing in the morning. Oh, and will address that infamous, engine/transmission to frame ground strap.


Cheers.

 

did you remove the alternator to clean its mounting points?

what a marathon ! That is one difficult job.
Don't put it back until you get the ground strap, otherwise you will have to repeat the job.

 

I may have lost track of the conversation a bit but, if you're running a new, dedicated ground to the alternator, there's no absolute need to remove it to clean the mounting points. Your new ground wire will do the trick. So long as the alternator is grounded, one way or the other, you're OK.

Cheers
DD

 

I did check this morning with my spare Lucas alternator and found that the easiest if not the best place to connect a ground strap is at the protruding "ear" where the belt adjuster bolts to.

Sure it would be a good idea to clean the rear or front side of the "ear" shiny, the bolt thread, and the side of the nut that will contact the strap shiny clean too.

 

Plus, it doesn't have to be a woven strap. Regular stranded wire will the trick. I don't think the electrons know or care if they're travelling through woven strands or spiral strands....although someone who knows a lot about electrons may well come along and prove me wrong !

Cheers
DD

 

a braided strap is more durable than stranded wire, especially in the engine compartment.

and Jaguar uses braided straps in critical places, not wire. Plus stranded wire is usually vinyl insulated, not exactly durable in the engine compartment, definitely not when grounding the O2 sensor, the heat will melt the insulation, if not a fire hazard.

 

Yea, good stuff folks. No recallable info on copper stranded vs woven. Just know that high current “burst” application’s where heat dissipation is involved, benefit from low gauge copper stranded. I believe(?) I’m dealing with continuous moderate(80A) current flow. I’ve got mesh on the way. I’ll try and access the mounting surfaces which pivot with these big ‘ol hands. If I can’t pull it off, I’ll just attach the mesh strap to the bolt which secure’s the trunion. Presently, I’ve removed the trunion(?), waiting on the strap. After that, I’ll check the devices which depend on 12-14.5V(not 17.5V) to see it they become operational. Transducer, speedometer, odometer, tripometer. Then, ima goin fur a long ride!

 

could the alternator's voltage regulator be going out? Have the alternator tested at Autozone, Advance, or O'Reilly.

 

Wow Jose, I must have been gone a while. Missed your comment about testing. I actually didn't want to remove it, wanted to try all the other possible solutions first. Plus, the unit charges beautifully @14.4Vrelig...., can't say religiously cuz it tends to "backslide" to 17.5V occassionally. So, I revived the thread because most post relating to the speedo. unit involve a faulty speedo. needle, I have a faulty odometer and DO NOT want to disassemble to lubricate the affected tumblers(?), since that would cast doubt on the validity of the cars 88,800 and sumpin miles. The post may be lengthy because I included a potpourri of info which I had not discovered in my 5 months of searching. Specified voltages and/or lack thereof, component removal/installation and where are the pictures of "what the HECK is going on underneath that intake?". Reflecting on some of the knowledge obtained from electronic school in 1988, factoring out the lesson's I missed to be with "BillieJean", I knew that the occasional 17.5V which the alternator was producing may have been the genesis of the problem since the Transducer and controller board in the speedo. unit have specified input voltages. I determined the Transducer was operational since data was being calculated and displayed by the Tripometer. A poster explained that alternators use an input circuit to detect battery voltage and then react appropriately. I read that less than a 1v voltage drop in battery detection circuit could reduce a 120amp alternator to 80amp, max. Lastly, EVERY poor connection in the charging circuit amounts to a resistance(voltage drop), and our (Lucas Alternators)probably default to 17.5V with a poor signal. Later schooling taught us that current(electrons) ACTUALLY, flow from the negative plates in the battery to the positive plates. The path my little babies take is: Neg. battery cable/Rt. Fender----(strap)Passenger lower frame/Block rear bracket----Block rear bracket/Block-----Block/Alternator bracket------Alternator bracket/Alternator case...see a theme? here's a pic......

 

........So, wasn't sure if the Pic was in the "post", went to look and messed everything up. I decided to inspect all(?)ground connections, positive also and mounting surface of alternator. Did not fully remove alternator, S.G. Barrett website gave instructions on removing alternator from mount, then flipping it over(with sway bar installed fully) to clean, inspect and access the voltage regulator. I realized the voltage problem could be attributed to a faulty voltage regulator, but the 37yr old connections needed to be addressed.Why half step on a first class car? After properly raising the car and taking a flat backed look at the alternator I had second thoughts about the whole thing, first class or not! Turned out to be EASY. I did the following:
Removed bolt from adjustable trunnion, rotated the nut on trunnion threads to allow trunnion to slide all the toward the oil pan for clearance. Used a thin piece of stick to pry alternator outward toward the lft. fender. Problem-Alternator insist on rotating back toward engine. Solution-Two 12" cable ties attached in series, insert tie into trunnion mounting hole then wrap the tie around sway bar. Alternator rotates VERY far, only stop's when contacting the P.S. hoses. So, if you don't have P.S......well, anyway, here's Pic:
After that I could view both mounting bolts, problem, I have XXL hands, so I attached box wrench freely to one end and used the socket on the other. Box wrench will contact something useful(choose wisely)Pic:


I then removed the BEAST. OMG!!
Removed both terminal connections, cleaned her up. Pic:
Jose, whom you recall posted earlier, convinced me to apply a dedicated ground strap directly to the alternator, then reach out to the driver's side cruise control area and attach to the sheet metal. He mentioned he sells them on his website. Reasonably priced and very well packaged. You WILL benefit from this UPGRADE. I attached the ground strap ring to the rear mounting surface via the bolt and nut. I located a suitable area to land the opposite ground strap ring, behind the brake line splitter, in between the doughnut spacer and the fender. Had to remove the paint. Bolt comes from inside the fender well through the splitter and attach's with a bolt. I reversed the direction of the bolt so the threads exit in the fender well. I applied an anti-corrosive to the area. I don't believe voltage/current in this area would affect the brake fluid operation. Pic:
I attached a cable tie around something(?)loosely to form a loop to suspend the emerging ground strap from the alternator. Pic:
Now the path for the ground side charging circuit is: Neg. Cable/Fender----Fender/Strap.....That's it. I did remove and clean the 2 positive battery connections, 1-passenger bulkhead side of battery and drivers side bulkhead. I did remove the transducer and tested operation with a drill for simulation. That's another post, with pictures.