How to Repair Partially Illuminated/Lit
Instrument Cluster Needles
1990-1994 Lexus LS400
LexLS: This tutorial is based on Richard's 1994 Lexus LS400 UK cluster (gauges are opposite, celsius temperature, etc). The following instructions will get 1990-1994 LS400 owners full removal and fix instructions. I want to note that 1995-2000 LS400's also used the same cold cathode instrument needles so the concept of this tutorial applies to second gens as well. However, the removal steps will probably be slightly different.
I know there are several methods to go about fixing partially lit needles. I will refer to this as method 1 because I have yet to see anything this detailed published (if I'm wrong let me know!). I would consider method 2 to be repainting the entire needle or even putting in a brand new needle. This is a common problem among owners and I hope this works for the majority but by no means do myself or Richard guarantee your needles will be fixed by following this tutorial.
A big THANK YOU to Richard for taking the time to initially write this up and submit pictures!!!
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This is not an invitation for you to carry out this work, merely a report on a method that proved to be effective in one case. I will not accept liability for any loss, damage or injury that arises as a result of you (or anyone else) attempting this.
The instrument cluster needles are miniature cold-cathode fluorescent tubes. Hazardous voltage is present, along with mercury vapor, and due care must be taken.
It would seem that the construction of the instrument needle is such that there is an internal electrode running along its entire length, and a conductive plastic layer covering the outside, except for a long rectangular ‘window’ i.e. the part that is to be seen. The inner electrode and outer sleeve are capacitively coupled, since the lamp operates at high frequency.
Often, the outer conductive sleeve will crack, thus there will be diminished light output from that point onwards. The sleeve can also peel away from the glass tube, causing uneven brightness of illumination along its length.
A popular method of carrying out a repair is to remove the plastic sleeve entirely and apply conductive paint to the underside of the needle. I believe this has two main disadvantages, namely that: (1) the paint may still crack eventually, and (2) the mass of the paint may alter the ballistics of the needle and, without adjustment of the balancing screw by trial-and-error, cause it to under-read. The method described below will have less impact on the dynamics of the instrument.
Tools Needed:
- Phillips #2 screwdriver
- Thin, artist's paintbrush
- Soft ½" or 1" paintbrush
- Dentist's mirror (optional)
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Parts/Supplies Needed:
- Silver conductive grease (e.g. Chemtronics)
- Cocktail stick
- Piece of thin card or photo paper, 11.5 x 11.5 cm, with 6mm notch from edge to center
- Eye protection
- Can of compressed air
- Nitrile gloves, non-powdered
- Several Q-tips
Before. You can clearly see the speedometer is the problem needle. Allow a full day for this job. It won't take a full day of course, but you don't need to be working under added pressure.
1) Remove the instrument cluster from your car. Remember that if you turn the car on with the cluster removed you'll have to turn the air bag light off later.
LexLS Note: Richard was able to do this job without removing the entire cluster from the car. I have written this up using the full removal method for illustrative purposes, but this job can be done either way.
2) Remove the instrument cluster cover. Step 6 is all you need to do and you then have access to the needles. 93-94 owners may have an extra screw to remove. Do not remove the black piece that surrounds the cluster face. Step 8 shows that piece removed and you don't want to disassemble that far.
3) Put your gloves on at this point. Carefully slide the notched piece of card down behind the needle. This is simply to protect the dial face. LexLS note: This card also gives you the opportunity to mark the needle position before beginning the repair, I would recommend doing this.
4) Determine where the break is on the needle. Power the cluster on, steps 1-2. Put eye protection on. Now, taking extreme care NOT to touch it with your hands (or anything conductive) gently press on the underside of the needle with a cocktail stick, starting at the pivot end. This is where the break is likely to be. If the dead part lights up while you're applying pressure then you've definitely found the point of failure. You could also try to see the fracture using the mirror, but it may not be visible.
Note: In this and the next picture the black part of the needle is not the original conductive paint but a plastic tube shown to illustrate the condition.
5) Remove power to the cluster. Apply a tiny amount of silver grease to the artist's paintbrush and carefully paint it onto the area where the break is located. If the sleeve has peeled away slightly, you can brush the grease between the tube and the sleeve, working it well in and right around the back. Clean off any excess with Q-tips.
6) Power the cluster on again. It might work! If not, repeat step 5 and try powering on again. If you hear arcing and see a wisp of smoke, you need just a little more grease. (You may also hear the inverter circuit buzzing.)
7) Carefully remove the card and dispose of it along with the used Q-tips and artist's paintbrush. You might want to change your gloves at this point as well.
8) Using compressed air and/or a soft clean paintbrush, ensure that the instrument cluster face and the back of the smoked cover are spotless before replacing the smoked cover and its 3 screws. Use caution with the compressed air as the needles are very delicate.
9) Cluster reinstall is reverse of removal. Enjoy your restored needle(s)!
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