Back when I had Supercat (my '95 4.0) it was just becoming the thing to upgrade to LED bulbs. Although I was afraid initially of doing that with the interior bulbs, e.g. might overheat a circuit, blow a fuse, etc. my fears turned out to be unfounded in that the LED bulbs use less amps than regular incad. bulbs. The results looked fantastic However, I did not replace the exterior bulbs with LEDs in that I was concerned that switching them out would mess up the Bulb Failure Warning System, given the differences in resistance between the two types of bulbs.
Iām now thinking of doing the same thing with Superblue, but this time would like to try to r/r the exterior bulbs as well. Does anyone know for sure if this would in fact mess up the BFWS, causing a false warning light? If so, what would happen if I just unplugged the BFSW module (or pulled the fuse for it, if there is one)? Since the LEDs are supposedly āgood for the life of the carā, seems I would have no need for a BFWS anyway, same being now obsolete ā¦
Yes it does give false readings. I replaced my rear lamp only with an led several years ado and had to pull the rear BFWS unit and adjust it to get the unit to behave. The current heats a bimetallic strip and it eventually breaks the circuit andnthenwarning light goes out. The adjuster adjusts the preset on the strip I think. Better to get rid of the system in the basis you stated about the reliability of the ledsā¦rather than waste energy on a resistor to increase the circuit currentā¦unless then device can be adjusted to the low current levels. That would be an interesting challengeā¦
I agree with Robin and Matt.I put LEDās in place of my brake light and rear turn signals, but as I have a Commercial Drivers License I am accustomed to doing a Pre-Trip check on my car, using my own eyes! Reliable enough for me! (Donāt think I will ever own a self-driving car either- whatās the fun in that?)
Interesting mechanism, in that it seems over the last few months my BFW light has been staying on longer and longer before going out, although I have no replaced any of the bulbs. Itās supposed to go out within 30 seconds of turning the lights on, if working properly, IIRC. It originally did that, but sometimes now it seems like it takes many minutes before it goes out. Sometimes even then it does not go out unless I turn the lights off and back on again and wait (and sometimes once again). btw, how do you adjust the BFW module? It looks like you have a pre-face lift XJ-S ā
is the module adjustable the same way on my face-lift 4.0?
Yepā¦an 85XJSHE. Mine was adjustableā¦a screw to increase/decrease sensitivity. I guess probably the contact that the heated bimetallic strip touches to switch ā¦the screw moves the contact for more or less bend to touch the contact. I set it to be on for about 30 secs then a flicker and the light goes off. There MUST be better ways to sense DC current levels nowadaysā¦I read about these things in Kirbyās bibleā¦so Inwould recommend checking there for more infoā¦
k. Thanks. btw, I know are you in NZ, but your last name ā¦ any chance you could be related to Betty Furness of old T.V. fame? She was the model lady who was demonstrating a refrigerator live during a commercial break on some old T.V. show back in the '50s and couldnāt get the door on it to open, much to her embarrassment.
Oops - I stand corrected on that particular incident, after reading up a bit on it in Wikipedia:
(One live spot featured a refrigerator door that refused to open, causing one of the most infamous bloopers in TV history; however, this was not Furness, but actress June Graham, who was substituting for her. For decades, Furness was ācreditedā for the blooper, until she set the record straight in the 1981 TV special TVās Censored Bloopers .[3])
We will be related in some wayā¦moderately uncommon surname that probably originated from a district of that name in the lakes district in Englandā¦but my Mum was Irish which bestowed on me a particular ability with refrigerator doorsā¦especially if they house vast quantities of cold beersies!!!
Well, I tried putting the LEDs in place of the festoons in the boot, and wasnāt too happy with the result. Seems like the LEDs are NOT brighter than the festoons for some reason, and maybe even throw off a bit less light. I do note that festoon bulbs emit light around them 360 degrees, instead of the LED replacements, which radiate light only 180 degrees (so be sure you mount them pointed TOWARD the lens, esp. w/o a reflector behind them). Maybe thatās why they donāt seem to light up the boot as well as the festtoons.
Worse, when I was done and put the light assemblies back in their respective mounting holes, they are not nearly as tight now in their holes as they were before removal. In fact, it took a bit of fidgeting with a screwdriver, a butter knife, etc. to even get them loose and to drop down to r/r the bulbs. Now they are a little loose at their back ends (or is that the way they are supposed to be?). I noticed that with both of them there is a spring retaining clip only in the fore ends - is that correct, or are they both missing one on the back ends as well? I didnāt have anything pop off the lights when I removed them from their holes, though.
btw, for those who have done the r/r with LED lights on their interiors, what LED bulb #s did you come up with for the map lights and the lights on either side of the sun visors? I have not found any of that size(s) online. The sun visor bulbs are capless, and the map lights are supposedly āhalogenā. Also, as to the door guard lights and the high mount stops, the LEDs would have to be red in color to keep from blanching out the color through the red lenses. However, I could find none of those, either.
Try superbrightleds.com, their selections work well. Their LED festoons work fine for the map lights. White LEDs are fine for the under door lights, it can shine through both the white and red portions of the lense with only a little difference in brightness depending on time of day
In 91 you have the newer design donāt you? If so I donāt have firm suggestions, just that I bought an LED headlight for my motorcycle from them and it seems to work great.
This is the upgrade I done 5 years ago. you can not use green as the dash filers did not look right with green leds. Switch functions are also transistor switched for colour change.
Very nice Just a few questions though: (1) the instrument lights appear to be flickering instead of steady ā¦ (?) (2) why are most of the indicator lights blue, instead of white? Did you install blue LEDs in those or is that just the way they filter out? (3) the front fog light button is green instead of yellow ā¦ is it that way OEM (I donāt have front fogs)? (4) if you didnāt use green LEDs with the turn signal flashers, what color did you use? Did you replace your interior lights (dome, map. courtesy, etc.) with LEDs too? If so, which sizes were you able to use for each of them? Iāve been having a big problem finding ones to replace the visor lights and map lights with, the latter of which are supposedly halogen bulbs.
btw, Iāve noticed it seems like more and more face-lift owners are dumping their OEM audio systems for aftermarket. Curious as to why ā¦ My only gripe is how the cassette player belt likes to break from time to time in them. I do like their weather radio feature though, and I donāt think any recent audio systems have that feature ā¦
The LEDs do not flicker in any way its just the camera does not like them . I will try another video with my later phone as may be better as they look much better when you see them ! The dials have blue leds to light them in a circle and red ones on the red section. The white leds light the miles and pointers. The OEM car has yellow and green for fog lamps but with jaguar the green and the yellow were on together. My version switches the blue off and the green or yellow on when selected. All warning light leds are true colours ie green indicator = green led. I had to custom adapt all leds for this job. All other lamps on the car are bulbs. My Audio unit is a much later ALPINE which is the same make as fitted in the later xjs cars. This has blutooth audio and streaming etc so much better to use. I also replaced some audio control panel leds so they can all match colours.
my fears turned out to be unfounded in that the LED bulbs use less amps than regular incad. bulbs. The results looked fantastic 
However, I did not replace the exterior bulbs with LEDs in that I was concerned that switching them out would mess up the Bulb Failure Warning System, given the differences in resistance between the two types of bulbs.
btw, how do you adjust the BFW module? It looks like you have a pre-face lift XJ-S ā
I do note that festoon bulbs emit light around them 360 degrees, instead of the LED replacements, which radiate light only 180 degrees (so be sure you mount them pointed TOWARD the lens, esp. w/o a reflector behind them). Maybe thatās why they donāt seem to light up the boot as well as the festtoons. 
Just a few questions though: (1) the instrument lights appear to be flickering instead of steady ā¦ (?) (2) why are most of the indicator lights blue, instead of white? Did you install blue LEDs in those or is that just the way they filter out? (3) the front fog light button is green instead of yellow ā¦ is it that way OEM (I donāt have front fogs)? (4) if you didnāt use green LEDs with the turn signal flashers, what color did you use? Did you replace your interior lights (dome, map. courtesy, etc.) with LEDs too? If so, which sizes were you able to use for each of them? Iāve been having a big problem finding ones to replace the visor lights and map lights with, the latter of which are supposedly halogen bulbs.
I do like their weather radio feature though, and I donāt think any recent audio systems have that feature ā¦ 