Howplum

Thank you very much for that George. I have passed the link onto my friend so I'll wait and see what he says.

Hopefully this link will take you in right direction: https://www.lexusownersclub.co.uk/tutorials/category/25-how-to-submit-a-guide-and-why/

Presumably you have tried the various sellers on eBay who are breaking LS400s?

The saga continues! I asked a friend who repairs computers to replace all 12 electrolytic capacitors, which he did, but it appeared to make no difference whatsoever. At the same time I removed the sender unit from the fuel tank and tested that, but it seemed to work correctly, i.e. the resistance readings were smooth across the full range of movement, with no gaps or peaks. A few days ago I managed to source a replacement unit for the princely sum of £25. The seller said that one of the backlights didn't work but the gauges worked fine and there was a big scratch on the front lens (easily changed). On connecting it I found the backlights were fine but a few of the tell-tale lights didn't work, but a quick clean of the contacts sorted that out. It does seem the fuel gauge it still a bit temperamental, but at least when it chooses to work, which is most of the time, it's accurate. At least one of the electrolytic capacitors is looking a bit suspect, so I'll get my friend to change all 12, again. The problem I have though is the mileage reading, which on the replacement cluster is 223,000! My car has only done about 80,000, so come the next MoT there will be a dramatic increase in the recorded mileage. I changed over the milometer display module from my existing cluster, but it made no difference, so I assume one of the components on the circuit board stores this information, but which one? If it can be identified then perhaps I can ask my friend to swap it over. Can anyone help please? I've had a quick look on the internet but have drawn a blank.

A very helpful post Kyle. Will you be adding it under the "How to" heading as well?

Thanks Phil. Hopefully I can identify the three(?) wires from the manual's wiring diagram at the multipin connector that lead to the gauge, although if I'm in the mood I might splice all 20 or so wires. It depends how tricky it is doing this in situ.

Another step forward. I recently met a friend of mine, who just happens to repair computers for a living, and he kindly agreed to replace all 12 electrolytic capacitors, which he did almost straight away. I optimistically thought that that would be solution to my erratic fuel gauge, but no such luck! The goods news is that the gauge now shows the correct fuel level most of the time, which reduces "range anxiety" at least. However, it does occasionally show empty when the ignition is turned on, so there is now an intermittent problem, which I would like to resolve. I have a Repair Manual on CD and managed to find a section on checking the fuel gauge and sender. As far as the fuel gauge is concerned the manual gives resistance values across the two pairs of connectors at the rear of the gauge. The approximate factory values are 151.8 Ohms across S+ and S- and 164.2 ohms across C+ and C-. The corresponding values on my gauge are 135.1 and 143.5, so approximately 12% lower than factory. The spare gauge I have from another cluster gives slightly lower readings than mine. I did wonder if the issue was with the sender unit, so carried out the following tests from the manual: 1. Remove the male connector from the tank sender unit, which should make the gauge show empty, which it did. 2. Jump pins 2 (violet) and 3 (green/white) on the male connector, which should make the gauge show full, but didn't, although that might have been because of my dubious jumper connections. 3. Applied an earthed test light to pin 3, which glowed only faintly, but I assumed this was something to do with the resistance provided by the gauge, which is in the circuit between the ignition switch and the male connector for the sender unit. I did find some further information on the internet about testing the sender unit. Apparently the resistance between the two outer pins (1 & 3) on the unit's female connector should be approximately 300 Ohms and the sum of the resistances between pins 1 & 2 and 3 & 2 should equal this. On my sender the readings were 298, 220 and 80 Ohms, so seem to work out according to the above. I haven't yet removed the sender to check the resistance throughout the whole range, mainly because the intermittent nature of the fuel gauge display happens without the car even being moved, or even started. When I first acquired the car last year I accidentally crushed the grey multipin connector that goes into the back of the cluster, so had to replace that and at the same time include a further multipin connector otherwise the loom would be too short. I suppose it's possible that there is a bad connection to one or more of the three wires that go between the cluster and the sender unit. As the gauge intermittently shows empty on start up this seems to me that there is an occasional break in the circuit somewhere, because it's the same result as pulling the connector off the sender unit. Is there an electronic component inside the fuel gauge that might cause this? I'm in danger of getting confused here, so any guidance for a electrical novice would be appreciated, and thank you for your patience in reading this.

But check all components of the part number carefully, which can really only be confirmed by removing the cluster. There seems to be quite a variety of different versions fitted by Lexus. I have been looking for several months for one to fit my 1995/6 LS400, so far without success, which is why I am persevering with the repair option, albeit with limited success so far.

As part of the ongoing saga to get all four gauges working, preferably at the same time, I carried out a small modification I found on the website of a US cluster specialist. It involves removing the front of the cluster to expose the cluster needles and carefully drilling small holes at the usual resting point of the speedometer and tachometer needles and inserting a short piece of stiff wire. I used 1.5mm wire and painted it black. So far it works perfectly, although it possibly affects the accuracy slightly, but not enough to be noticeable.

I found four for sale, all with a variety of issues, two of which have/had rear subframe issues (note to self - de-rust subframe sooner rather than later). I suspect in the not too distant future cars like this will be broken for spares because they are not viable restoration projects, unless values increase significantly. I'm glad I only paid £400 for mine! However, I quite like the wheels on this one:

What's the consensus amongst those of us who run older models? I for one will probably be using Tesco's higher octane alternative instead of an additive. Obviously it's more expensive, but for a limited annual mileage not enough to even consider selling my LS400.

I would say it's difficult to answer your first question with any accuracy because the wear rate will depend on a number of factors, especially driving style. When you inspected the discs were you able to check the inside as well? Also, it would be worth checking the rear discs and pads. It's possible than one or more piston might be seized in the caliper, especially in the rear calipers, which don't work as hard as the front ones. I believe in theory new pads and discs should not affect the pedal travel, only the efficiency, assuming that the rest of the system is working correctly. After all, the system is 22 years old, so not all of the components may be working as the manufacturers intended.

Nevertheless, it's possible that asking prices like this will have an effect on prices overall. At least, that's what I'll respond with the next time SWMBO queries a major expenditure on my project LS400!

I noticed this new advert on Car & Classic: https://www.carandclassic.co.uk/car/C1368563

I've done the job and the only special tool I needed was to hold the harmonic balancer (crankshaft pulley) steady whilst I undid the bolt in the middle.

Thanks Steve, that's very helpful.

Well, the speedometer and tachometer still seem to be working as intended, so installing stops seems to have worked. The fuel gauge refuses to budge from empty, regardless of ambient temperature, so my plan now is to replace all 12 electrolytic capacitors on the basis that they are all of the same age. This is assuming that one or more might be the culprit, but I have to start somewhere, because I can't even find anyone to test the circuit board. I have tried ringing round local electronics repairers, but no-one seems interested, so I am going to have a go myself. To that end I have ordered an adjustable soldering iron kit from Amazon, which gets good reviews, so should be better than my very ancient one. I have a few faulty electronic items which I will experiment on first though. I shall take the opportunity to practice reflowing soldered joints as well. For the experts amongst you I have some technical questions. I can find exact matches for all but two of the capacitors, so need to to know if ones of a higher, or lower, specification can be used instead. 5v 1uF - The only capacitors I can find with a capacitance of 1uF are 16v or more. As far as I can tell 5v is no available anyway. 25v 850uF - I can only find 820uF or 1,000uF at this voltage. Which is better, or does it have to be an exact match? Is physical size a potential issue? Please reply in layman's terms! Thank you.

After all my fiddling about I went for a drive and both the speedometer or tachometer needles worked fine, but is it a permanent fix? Only a daily drive will tell me - any excuse to use it! Also, the fuel gauge sprang into life straight away, but again, will it tomorrow? The temperature gauge still has a mind of its own, in that it doesn't want to return to the correct rest position when the ignition is turned off, so is now over stating the temperature, although it seemed OK when I was putting it back together. I appreciate they are very delicate instruments, which is why I have been so careful, but I will try and lay my hands on yet another one. To add insult to injury, the airbag warning light is now on permanently, so yet another little problem to fix.

Apologies Steve. The previous photos I included were of the 1997 circuit board and, as you say, the EC next to the orange connector does look suspicious. However, my own circuit board looks OK, superficially at least.

Phil, you are right about the gauges themselves being interchangeable, at least between the 1996 and 1997 versions, because did swap the temperature gauges over. I take your point about the effects of corrosion, but at some point last year Steve did very kindly sort out the lights, and removed a lot of the corrosion in the process, so hopefully it will no longer be a factor, but who can say for sure? As far as the speedometer and tachometer gauges are concerned I have no idea whether those on the 1997 unit have the same sticking issue, so instead opted to install stops, as mentioned on the US website I found. This is the result: Hopefully they will do the trick. Obviously they will give a slightly higher reading on both gauges, but probably not enough to worry about in the real world. Which just leaves the fuel gauge. Steve, to my untrained eye the electronic capacitors look fine, but obviously you have a great deal of experience in electronics so you could well be correct. The large one above the orange connector is indeed 470uf 25v, and the two even larger ones to the right of the yellow component are 820uf 25v, if that's relevant. Perhaps one option is to ask an electronics engineer to replace all 12 ECs and be done with it. Hopefully I'll get there!

Steve, that was one of the companies that said they couldn't test it. As I've discovered, there seem to be quite a few versions of the cluster over the years.

I should add that my attempts to track down a used unit have so far been unsuccessful, mostly because the relevant sellers on eBay don't have the common courtesy to reply.

My cluster issues rumble on. I have sent the unit to both BBA-Reman and ECU Testing, both of whom sent they couldn't test it because they apparently didn't have the correct jig. All the other companies I found weren't interested, even though Cluster Repairs UK had a page on their website specifically for the LS400. However, I have found a small company in Aylesbury who, when I rang, didn't say no when I asked if he liked a challenge, so I have sent him some pictures, since when I've heard nothing. However, I shall contact him again next week, hopefully armed with more information. I have a wiring diagram, so have established which three wires are from the fuel tank sender, and which pins they go to in the large grey multipin connector. Tracing their path on the PCB is a job for an expert though. I have found repair kits (3 electrolytic capacitors) for earlier models in the USA, but no mention of post 1995 models, which I assume must be different, and probably more complicated. Does anyone happen to know which of the 12 electrolytic capacitors relate to the fuel gauge? See my post on February 23rd. The temperature gauge was riding over the stop, so the needle was starting from a lower point than it should, but having stared at it and prodded it gently it seems OK now, at least off the car. Regarding the "sticking" speedometer and tachometer needles, there seems to be no stop for the needles, which must be inside the sealed unit. However, I did read on one US repairer's website, taninautoelectronix.com, the following: "Please Note: Because these clusters don’t have a needle stopper from the factory for the mph and rpm, we add that on our repairs and rebuilds. This prevents the needle from sticking and makes the life of the motor longer but in order to do that, we put the needle stopper a little higher than 0 mph/rpm. This makes the needle show it’s on 1mph-2mph when the cluster is off/car is stationary." This makes sense, and at least I have a spare cluster to experiment on.

Economy model - 1.1 litre and 75 bhp!

Good point! I removed my wiper arms last year to repaint them and I don't remember it being too difficult, just a bit unusual because of the pantograph arrangement on the driver's side. I await clarification before jumping in again!