burghard

I just talked to the Lexus Customer Service line and asked them if they made a change to the board or its components. The rep could not find any changes to the '94 cluster in his database. That does, however, not mean that Nippondenso did not change anything on the board. I asked him to do more research to find out whether there was a component change. I will keep you posted if I ever hear back from him.

I again expressed my dissatisfaction with this failure and the expensive Lexus remedy. I encourage all of you to call the Lexus Customer line (800.255.3987) and at least register this problem with them. Then they can't say "we have not seen this problem".

Herm

I looked over my 93 LS service manuals(page BE130). Seems to me the problem is the power supply for the six Cold Cathode lamps in the instrument cluster. Two are used for illumination (circular white) and four are used as indicators (pointers) for the speedometer, temperature, tach, and fuel gauges). These Cold Cathode lamps - sort of a cross between neon and fluroscent technology require a high voltage supply - I suspect that is where the failure is occuring, to develop the high voltage there is probably a chopper circuit and transformer.

The good news is that the cluster appears to come out very easily with a few screws (page BE137)- as someone mentioned in an earlier post. The bad news is that there does not appear to be a circuit diagram of the Cold Cathode power supply in the RM300U1/RM300U2 manuals. BUT there is apparently a procedure for powering up the cluster outside of the vehicle (BE168-169), this may allow someone with electronic troubleshooting/repair training-experience to find the problem.

Perhaps there is additional technical info in the EWD1640 electrical wiring book but I do not have it (anyone know?)

If anyone finds the bad component(s) it would be great to post the info. Better still, a recall would be nice !

My 93LS is working fine now but the previous owner told be that he had the problem fixed a few years ago ! Sure sounds like a bad design to me - since the speedometer pointer can go out I certainly think it is a safety issue. Sounds like this failure has been occuring for many years and is a comon problem !

Hope the above helps - Herm

hyperopt

The problems many Lexus owners experienced with their instrument clusters are most likely due to power supply circuitry. On contrary to earlier posts, electronic components do NOT have infinite lives. It is not unusual for some electrical components to go south after 10years of service. Some will expire earlier depend their qualities and loads.

healerhand

I replaced my cluster few months ago. Lexus are so advance in engeineering. I opened up the broken cluster and noticed all the gauge pointers are flourensce bulbs.

Herm

In my opinion, based on about 30 years of relevant experience, a modern well designed and built automotive electronic circuit could easily be made to last for decades. (There are exceptions of course for very high power or very harsh environments - certainly not the case here). Big factors are the quality of the components used and reserve margins built into the design.

stock300

This is also a problem on the SC300/400's although the needles are red instead of the white on the LS400. My 95 LS is OK so far and I keep the intensity down. My SC's speedometer needle is starting to flicker so that has me worried.

turbosix

http://home.vicnet.net.au/~pgscott/d...dashrepair.htm

here is a link to a guy named scott's VERY extensive Australian Soarer (sc's over here) website. the dashes are very similar, so most of the information should apply. This is a step by step dash removal and repair. If you cant do the electrical work, you could probably print out his website and go buy the parts needed, and take it to maybe a tv repair shop to have them have a go at swapping the parts. Its very easy if you know how to solder.

vdo

I have 94 LS400 that exhibits the exact same problem. The whole dash will not light up when the weather is cold, causing driver not to see any of the warning lights, speed, or fuel level. I believe this leaves the car occupants in a very dangerous situation. The Lexus dealer wants an absurb amount of money ($1200) to fix problem, which I believe is a factory design flaw and needs to be recalled. In addition to this, my tachometer needle only lights up half way and the A/C-clock lcd panel is half black. Not quite something you'd expect from a company in relentless persuit of perfection.

I have already submitted a complaint with the NHTSA and would incourage any of you reading this that have the similar problems to do so also. You can submit a complaint online here:

http://www-odi.nhtsa.dot.gov/ivoq/

A lot of cars get recalled for less dangerous reasons than this. This must not be tolerated, especially since this is not just a lighting issue that is problematic at night. We NEED the gauge lights to see the instruments in all lighting conditions.

Vincent

'94 LS400

Jim Walker

YES!!! I found and fixed the problem with dash lights. Thanks to burghard. He sent his bad boards to me and I was able to troubleshoot and repair his and mine.

After many, many hours of exhausting and painstaking troubleshooting and reverse engineering (along with a little guess work) I finally found the problem. The problem I found is that some components have changed value over the years, specifically, several capacitors. These capacitors, along with some inductors form a tuned circuit. When the capacitors changed value, the circuits became detuned and damaged an IC (Integrated Circuit). All these components cost less than $20. However, all these components are "surface mount" devices of very fine pitch. It requires specialized equipment to desolder these components as well as to resolder the replacement parts. I do not recommend that your neighborhood electronics repair shop attempt repairs on these boards. The copper traces on the boards as well as other near-by components can be easily damaged if the proper equipment is not used. I do have the proper equipment and experience to do these repairs. I also have purchased a supply of the needed components to make the repairs. In addition, I am in the process of fabricating a test fixture for testing the repaired boards. My wife has objected to my continuing the use of her instrument cluster out of her car for this purpose.

If you want more information, email me at jimlwalker@sbcglobal.net and I'll email all the info back.

Jim Walker

turbosix

so, did you guess and do it all yourself, or did you look at the guys page up there i posted the link to.. he did/does exactly what you are talking about.. it wouldve been a ton easier to just see what he did and do about the same thing

blange400

Why not just send your cluster to

Mikado Engineering in San Fran.
1435 Huntington Ave
SF, CA 94080
650-615-9966

in 24-48 hours plus shipping time, he will repair flickering speedo needles alot cheaper than replacement. About $125 I think. 2 needles for $175. He also does the light bulbs cheap too.

The guy has been doing them for a long time.

So why not?

nextlevelcoupe

iTrader: (1)

what about converting those same cathode tube(flourescent tubes)in the ls to the sc400 dashboard?i bought the parts that light up the speedo and the tach but,i have nothing to power them up with.what can i use to power these tubes?

nextlevelcoupe

iTrader: (1)

here's a pic:

Jim Walker

To light up a florescent lamp, you need a special power supply called an inverter. An inverter basically converts the 12.6 volts DC into a higher voltage AC. When you first apply power to a florescent lamp you need to apply a higher voltage initially just to get the lamp to "fire". Once it is fired, the voltage required to maintain conduction is less. That initial startup voltage is also known as the "strike voltage".

The normal run voltage is just called lamp voltage. Normally the strike voltage is 2.4 times the lamp voltage. For example, if your lamp is rated at 1000 volts, the power supply should be capable of applying 2400 volts initially.

The voltage requirements of your lamp is primarily determined by the diameter of the tube and the length of the tube. There are other factors also such as the gas mixture that is contained in the tube as well as some other variables.

What is the diameter of your tube and what is the length of your tube if it were straight? (that is not a 'personal' question!!!!)

Jim Walker

hanklehrer

Hi,

Thanks to Jim Walker and Burghard, my dash lights are now repaired. I took Jim up on his offer to repair my board and the process went off smoothly. Here's how it worked.

1. I sent a payment to Jim on Paypal on Monday.
2. He sent me the boards 2 nd Day Air and I got them Wednesday.
3. My mechanic installed them today (3 hours labor) Thursday.
4. I drove home a happy camper and will 2 nd Day Air my boards back to Jim tomorrow (Friday) and he will return my core charge.

I actually got Burghard's boards (and his mileage) and someone will get mine after they are repaired. Jim commented in an email that it took courage for me to send money to someone I knew only by email but he appeared to be an honest and straight forward guy through his communcations and email so... I've been doing this on eBay for quite some time with few problems and for a lot more money and I think the people I have been dealing with have been very honest as have I.

I have given Jim's name, email, and phone to my mechanic on her request. There will be more work for Jim I expect.

Now the big test will be tomorrow AM when I crank up the Lex which has been sittng in the cold for 16 hours. I expect no problems and should "see the lights!!!!" (Note: I took the car out for a drive this AM and all lights worked perfectly)

Nice work, Jim.

Hank