I recently purchased TPS and now that it got here I see that it is not a direct fit by any means. I believe this one is off a later year (90-91) XJS V12, while mine is 1982.
I really would prefer to make the red one fit, since $50 is one heck of a deal, compared to ~$200 for the older version.
I checked resistance and both seem to float between .2 and 5.9 KOhm, connector is identical as well, so it seems that I in for some mechanic adapting, or is there something else?

 

At some point Jaguar discontinued the early Bournes TPS and replaced it with the later red type (orginally used on Marelli cars, I think). An adapter/mounting kit was sold separately for (as I recall) a rather silly price. I'll try to find a pic.

Might make a pleasant afternoon diversion to fabricate something on your own. My memory is too foggy on the details to provide any clever ideas though

Cheers
DD

 

So these do interchange, as long as I manage to mount red one in place of the original black?
As you might have noticed, I already rebuilt original unit, so it is only a matter of time, until it fall apart again.

Since you are familiar with the subject, what should the resistance at idle?

 

Found this, interesting...
http://www.jagrepair.com/images/Auto...TSB%20C-11.pdf

 

There ya go....now you know what a "mounting kit" would look like!

Cheers
DD

 

I dunno. I never checked one for resistance, only voltage

Idle voltage should be about .32v-.34v and WOT voltage should be about 4.8v-5.0v, as checked with the meter on the red and yellow wires with the TPS attached to the car's harness. Of course, the voltage change should be smooth as the TPS is turned....no dead spots or sudden spikes.

Cheers
DD

 

$50 is a pretty good price. I did the mustang conversion and it causes a significant lag so I'll be changing it.

 

You are welcome to my "rebuilt" unit, when I am done adopting the red one. Mine works 100%, but for how long I do not know.

 

Cool, thanks!

 

Mish, they are 100% interchangeable. The setting at idle is 0.32V +- 0.02v.

The red one is a far more durable item. I did not wish to pay the absurd $150 Jaguar price for the adapter kit so this is what I did:

Fabricate a 5mm square alloy plate with three holes to bolt up the the old potentiometer holes on the capstan. Drill a larger hole in the middle to accept the spindle. Remove capstan spindle (two little bolts on the top) and offer up the new potentiometer to the plate, see how proud the spindle is when touching the Potentiometer spindle. Allowing for the depth of the slot needed in the capstan spindle to engage with the poentiometer, cut down the throttle spindle and slot it to engage with the potentiometer.

Then offer up the potentiometer, and mark a suitable place on the plate for the fixing/adjusting screws. Drill and fix, then adjust closed position voltage.

Glad the manual box is sorted. Congratulations.

Greg

 

Gred, this is what I was planning to do today, except by idea was to have 3 4mm bolts welded up to throttle plate and have new TPS seat on these and some plastic spacers. In any case, capstan slotting and mating I was planning to do just like you did.
Thanks for the voltages, I assume I get those by slightly moving the TPS at idle, until perfect voltage is achieved?

Thanks

 

Yes, the original set up has elongated slots so it can be adjusted, so that's what you have to do to the new fabricated setup.

When you're done with the old one let me know and I'll give you my shipping address!

 

Yes, exactly that. I found that it is easiest to do it with the capstan assembled but not bolted to the engine, so in effect, you can hold it on its side, or upside down to do the adjustment and measurement.

Greg

 

Do I adjust with motor running, or just with ignition on?
I am having tough time finding consistent spot with .32V. I seemed to have adjusted it perfectly with ignition on, but when I started engine it showed nearly .8v.

 

Ignition on, engine not running. The best place to put the probes from the meter is into the wires just as they go into the back of the loom plug, rather than the pot plug. The reading should go from 0.32 to nearly 5v at WOT.

It is easier if someone else is turning the capstan, and yuo are doing the meter / probes only.

Greg

 

So the voltage is measured between then yellow and red?

 

Sorry Mish, I cannot remember the colours! But one wire has permanent 5v feed, one has nothing and one has the variable feed that alters with the position. You need to find the variable one and measure that, with the other probe going direct to earth. I clipped the earth onto the engine somewhere, and tried each of the three wires until I found the one that changed with the capstan movment.

Greg

 

Yes, the red wire + earth was giving me the reading.
I just bought Ford TPS for $25 and will try to mount that, since it has minimum position of .38v, this way idle is guaranteed to be perfect, unlike damn Licas with minimum position of .18v.

 

I used the Ford unit and found I have a hesitation, especially when the engine is cold.

 

0.38 is not 0.32 +-0.02 Mish! Are you sure the pot is not moving a bit with the capstan? After your triumph with the gearbox, I am sure you can nail the correct pot !

Greg