Dim Dash lights on my XJS

What is a good replacement bulb for the old dash/instrument lights???

Garry,
Dim instrument panel lights is a common complaint among prefacelift XJ-S owners and you will find a lot of posts about this in the archives. I think some have replaced the original bulbs with LEDs, but I canā€™t speak to that modification.

I fixed this problem in my wifeā€™s 1990 XJ-S convertible in two steps. In the first step I removed the instrument panel and partially disassembled it to remove the green plastic lenses over the bulbs that discolored to brown with age, reassembled the instrument panel and reinstalled it. My wife was pleased with this improvement but asked if I could make them even brighter.

In the second step I made a jumper plug and completely bypassed the dash light rheostat and this made a big difference. The original dash lights are now nice and bright white and I did not change the bulbs. I thought that bypassing the rheostat shouldnā€™t make a difference, but it sure did when I tested my jumper plug. Perhaps the rheostat was bad? The only disadvantage to this modification is that there is no way to adjust the dash light brightness, but that is no problem for us since we both like the nice bright dash lights now. I did not install any new bulbs.

So this modification worked out nicely, my wife is happy, and except for my time this didnā€™t cost anything to implement.

Paul

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I broke off the green plastics that give the little bulbs their color, and replaced bulbs with bright blue LEDs. Nice and bright! let me know if you need part number. LEDs were $4 each.

The rheostat is the actual problem indeed.
In my XJ, same set-up, I discovered that the rheostat arm was never reaching the end of itā€™s travel, and never had zero resistance. I soldered a little plate to extend the direct contact between the arm and the base.
The difference in light was day and night and I still have a functioning rheostat.

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Led conversion kits are available https://www.bettercarlighting.co.uk/index.php?searchStr=XJS&act=viewCat&Submit=Go

Thanks Paul! I have been planning to try this (bypass rheostat) for a long time, wasnā€™t sure that it would have any affect. Glad to hear that it seems to make an improvement!

Bob,
Bypassing the rheostat made a big improvement in the instrument panel lighting in my wifeā€™s 1990 XJ-S convertible but as Aristides points out it very well could be that we had a faulty rheostat. The instrument panel lights are nice and bright white, my wife is happy, and I have many other projects to do so this is my solution to to dim instrument panel lights. :wink:
Attached are some pictures of the jumper plug that I made using a similar plug that I harvested from one of my 3 Series III XJ6 parts cars, soldered the wires together and covered with shrink tubing. I first tried out my rheostat bypass idea using generic jumper leads and the improvement was so good that I created the permanent jumper plug. I also attached a tag to the plug to document this change for someone in the future who might wonder why the rheostat doesnā€™t work.
BTW, if you or anyone else reading this would like a jumper plug just send me a PM and i will see if I have any more. I already sold a few to others who read my posts in the archives and contacted me, but I am certain that I have several more of these connectors in the harnesses that I removed from my parts cars.
Once the jumper plug is made it is a simple matter of disconnecting the connector leading to the rheostat under the dash and plugging in the jumper plug.

Paul



Aristides,
That is interesting about your XJ saloon. This dash lighting modification was so successful in my wifeā€™s 1990 XJ-S convertible that I made the same modification in my Series III V12 Vanden Plas because I found those lights too dim even with the rheostat turned to full bright. After bypassing that rheostat I have nice bright instrument panel lights in that car as well but no dimming capabilities, which is fine for me.
I have some spare XJ rheostats from my parts cars and maybe I will play around with them in the future to see if I can do something like you did.

Paul

That polarized plug is same as used on the cruise bellows; when I needed one of those, I just bought a ā€œ4 flatā€ trailer harness and cut off the unused terminal. They are only a few bucks at any auto parts.

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So I got a jumper plug from @Paul_M_Novak and just recently installed it. I took before and after pictures which are below. Definitely not prize-winning photography, but I think you can see the difference.

Before:

After:

Iā€™m glad to have found this topic, despite it being more than a year old. Iā€™ve been troubled by the dim instrument panel lights, as well as some of the other dashboard lighting (probably bad bulbs for the latter). I wanted to see what Aristides was talking about with respect to the rheostat. My car is a 1990 XJS convertible (OTS I guess is the correct term). Iā€™ve got the instrument unit out and the main light switch bracket moved out of the way. However, the rheostat is jammed up against the left vent and tubing. I donā€™t want to break anything, so Iā€™m hoping someone can tell me how to get the vent out of the way.

The square tube overlaps the hard plastic case of the outer vent. It would seem that there has to be a way to get the vent out without destroying the wooden fascia. The car has 75K on it so Iā€™m sure that the connection is a bit dried out and stiff. Does the outer adjustable vent component just press into place? Are there plastic pressure clips on it?

If I canā€™t get the rheostat out safely, Iā€™ll just do the Paul Novak technique. Shouldnā€™t be hard to manage at all.
There are also 2 loose wires with female blade connectors. Iā€™m thinking that they attach to the rheostat for its lighting? Anyone confirm (a black and a red I think)?

Finally, do the dashboard switches (courtesy lights for example) just click into their slot like the power window switches or is there some other connecting mechanism?

Thanks for any help in advance.

Eric

Hi Paul,
I purchased a 1991 XJS classic collection convertible. Could I purchase one of your Jumper to Rheostat bypasses? If so, let me know how to proceed with payment/delivery details for you.

Aggy,

I am sorry but I sold all of the XJ-S dash light rheostat jumper plugs that I made and I no longer have any Series III XJ6 parts cars to harvest more jumper plugs from.

In the email string above you will find a post from Robert King that says that he found these electrical connectors at local auto parts stores for a few dollars. I recommend that you print out a copy of the picture that I posted showing the jumper plug and bring that with you to your local auto parts store and find a similar plug (which may have four or more wires, but you can cut those unneeded onew off). The jumper plugs that I made have two female connectors and one male connector. All I did to create the jumper was cut the connector wires to an appropriate length, slide some shrink tubing onto one of the wires for later use, twisted all three wires together and soldered them, then slide the shrink tubing down over the solder joint and heated up the shrink tubing with a heat gun to cover the solder joint.

Good luck.

Paul

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Sounds like that is a great solutionā€¦ I put LEDs for turn indicators and high beam.but the rheostat trick sounds great

scrimbo,
Bypassing the instrument panel lighting made such a big improvement in the brightness of the lighting in our 1990 XJ-S convertible that I made a similar modification in our Series III 1990 V12 Vanden Plas. My wife used to complain about how dim the instrument panel lighting was in both cars when she drove them at night, but not any more. :grinning:

Paul

Sounds like I will be delving into the rheostat and soldering on a piece that allows it to go to 0 ohms.

Should brighten up my life some.

Jerry,
I considered doing something like that, but decided to just add the jumper to bypass the rheostat completely. I did this because adding the jumper was quick, easy, and reversible if a future owner wanted the rheostat so that he could set the instrument panel lights to ā€œDIMā€ or ā€œDIMMERā€. :wink:
I also had several connectors from the wiring harnesses that I harvested from my Series III XJ6 parts cars, so all I needed was my time with my soldering gun and some heat shrink tubing and a heat gun all of which I had on hand.

Paul

Paul, my understanding of what was stated is that adding a small tab to the rheostat allows the rheostat to go from dimmer to dim to full bright as the rheostat now actually goes to 0 ohms ā€¦ yet is adjustable to full ā€˜dimmnessā€™.

It isnā€™t soldering a short across the rheostat to create full brightness.

Thus, there is no reason for anyone to want to reverse it to dim and dimmer ā€¦ at least no reason I can think of why someone would want to remove the ability to get full brightness.

Pulling the green shades off and a general cleanup is plenty bright on my 90.

Itā€™s important to remember that while it might look cool to have a lighthouse in oneā€™s instrument cluster, itā€™s counterproductive when driving at night. You need them bright enough that you donā€™t have to squint or take an undue amount of time to focus and check your speed or what have you for sure, but if you have them too bright youā€™ll have some lag time for your eyes to adjust to the darkness when you look up again, if they ever do. They have dimmers on these because everyone is different and all old cars do get dim with age, I still turn most of them down a little when they are in good order, and Iā€™ve got crappy eyes. So donā€™t get carried away. :slight_smile:

Generally speaking, red or reddish orange is ideal for preserving night vision.
Green tends to reveal more detail (like instrument numbers) hence itā€™s popularity. But you find some shade of red in places where it really matters. BMW has used a pretty carefully chosen reddish orange for years just for that reason.

Such as flashlights private pilots use (or at least did back when I flew). Mine had red and white beams.

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