Electrical Fault?

Fringfordjohn · November 19, 2014

Hi Everyone,
This is my first post on this forum, although I have been reading it for many years.

Last week I was driving up the M1 to Birmingham in my 1999 Mk 4 (owned for twelve years and only 37000 miles from new) and feeling at peace with the world, as one does when driving a Lexus, when as I approached the M1/M6 turn off, without warning the instrument panel lights went off and the gauges all dropped to zero. Simultaneously the heater stopped working, along with the flashers, the wipers, and although the sat nav screen remained lit, it stopped moving.
Mercifully the engine kept running, as I was in the narrow roadworks section of the motorway, with no possibility of being able to stop safely anywhere.
As the car was still running I carried on to the Corley Services on the M6 to assess the situation. As I pulled in to the services I realised that the power steering was also not working properly.
I didn’t dare to switch off the engine, in case it wouldn’t start again, so I sat and consulted the hand book on the section about fuses. That told me precisely nothing, but whilst I was sitting there pondering what to do next, for no apparent reason the instrument panel came back on. Also the heater restarted, the wipers and flashers came back on and the satnav screen went out and then came back on showing the correct position. The power steering also started working again.
As I badly needed to go into the services (old age) I took a chance and switched off to see if the car would restart, which it did. I then completed my days travels without further incident, and I have use the car a couple of times since without any further problems.
Thinking about it afterwards, it almost felt like a thermal overload cut out cutting out and then resetting itself, but I didn’t think that these cars had anything like that on them. I suppose the fault lasted for about half an hour in total.
I suppose the next thing to do is to pull all the fuses to see if any of them are faulty, but of course everything is working now so it will be difficult to find. What ever possessed the designers to put the fuse box in such an inaccessible position in the drivers footwell I don’t know.
However before going any further I thought that I would ask if anyone else has had a similar occurrence, and if so what the cure was.
Many thanks in advance.

cruisermark · November 19, 2014

this points a faulty ignition switch - i had this problem on my mark 4 3 years ago - after replacing the switch never had the problem.

next time the problem happens try wiggling the key in the barrel to see if it makes a difference - i will try to find my old barrel and post up a picture

hope this helps

ambermarine · November 19, 2014

John

It seems to be a recurring problem on the Mark 4, I have had two instances of this phenomenom and both times exactly the symptoms you had.My car as only done 26k and it first occured for me at 23k.

I have investigated the scenario and it seems the ignition switch on the Mark 4 it not integrated into the ignition barrel as it is on earlier models .The switch is screwed onto the end of the barrel and the ignition wiring is plugged into it .Somewhere there is a design fault which causes the switching to disengage and hence the blackout scenario.

I have also discovered that this switch is made by an outside supplier and is fitted to a lot of Totota and Lexus models were it as also caused this problem. This particular switch is also supplied to other manufacturers of motor vehicles.

I toyed with the idea of replacing it but as my car as done very few miles it is not wear so the problem could re-occur even after fitting a new switch.

This last weekend I have completed a 750 mile round trip to England through various driving modes Motorway/rural /town and city and had no instance of the problem .I now know what it is and a tiny touch of the key and it resolves itself so I think I will leave it alone unless it gets worse.

Malc · November 19, 2014

well well well, .... this was aN annoying problem too on my Mk3 a couple of years back .... scared me rigid at the time but as you say, stop the car somewhere safe, turn it all of and BINGO ..... it all starts up again ok and lasts until .... well, the next time.

It hasn't happened to me for absolutely ages now but when it does I know the simple solution.

My indy reckoned it was probably the ignition barrel too and if it happens again I might get him to sort out the problem.

It's not just Ls400s, it happens to VWs too he tells me.

Maybe it's just age related and not using the car enough .............. maybe the Ls is telling us not to take it's apparent brilliantness for granted eh !

Malc

Spottedlaurel · November 19, 2014

A very useful post and series of answers. My Mk3 has done the same thing three times now, a little alarming at night but the classic switch-off-and-on-again solution has done the trick each time. On two of those occasions I had just gone over a bump in the road (level crossing etc).

I had to replace the ignition switch on my 1993 Camry, on that I thought the problem was due to the less-than-neat alarm/immobiliser installation (done by the importer/dealer, not factory?). I replaced it with one off a later model which hadn't been fiddled with and all was fine. Could the same non-factory fiddling cause the issue on LS400s?

I wonder if one of my Camry switches would work on the Lexus, if it keeps happening?

steve2006 · November 19, 2014

Part number is 84450-16080 and it is the same as a Toyota Starlet 96-99 models which will probably be cheaper than the Lexus price around £85.00!

cruisermark · November 20, 2014

Here is a picture of the faulty switch

What happens is over time for some reason the back becomes loose as shown by the arrow - inside the switch is a series of spring loaded copper discs which rotate to make or break an electrical connection and i think whats happening is when the back becomes loose it creates enough Loosiness between the discs to break the electrical connection which causes the blackout.

wiggling the key corrects

hope this helps

Fringfordjohn · November 20, 2014

Hello again, and thank you all for your replies, and especially to Mark for the picture of the switch. It’s a relief to know that the problem is only caused by a faulty switch, and not by something buried in the electronics as I had at first feared.

At least I know what to do now if it happens again, wriggle the key, or if not, stop and switch off and on again.

I have to say that as well as my LS400 being the nicest car that I have ever owned, its also been the most reliable by far. Its certainly the only car I have ever had where after fifteen years everything still works, even the radio aerial.
Unlike my wife’s Renault Scenic which is the most unreliable car I have ever owned and has cost me a small fortune.

Anyway, thank you all once again for your help

Kind regards, John.

Mike Scott · August 13, 2015

I have exactly the same problem with my1999 LS400 can anyone tell me how to remove the ignition switch so that I may replace it. I'm new to the forum & any help would be appreciated.

Thanks

Mike

plexus914 · August 13, 2015

I have exactly the same problem with my1999 LS400 can anyone tell me how to remove the ignition switch so that I may replace it. I'm new to the forum & any help would be appreciated.

Thanks

Mike

Hi Mike, see ambermarine's post:

"The switch is screwed onto the end of the barrel and the ignition wiring is plugged into it ."

steve2006 · August 13, 2015

I'll take a look at my 1998 LS400 over the weekend and come back with a "how to" Mike.

It tells you how to check the switch in the workshop manual but not how to access it

Mike Scott · August 14, 2015

Thanks Steve, look forward to hearing from you.

Mike Scott · August 14, 2015

Many thanks, I've checked out ambermarine's post but what I would really like to do is to remove the ignition switch, together with the attached wiring & either repair or replace it.

ambermarine · August 14, 2015

Hi Mike

Just picked up your thread and the issue with the ignition switch.

I have not replaced mine and have had a couple more incidents were the the electrics have failed and a touch on the ignition key resets it so I am fairly certain that the switch is the problem and the contacts inside are at fault as this is a common fault on the Mark 4 and various other manufacturers models it is also fitted too,I have concluded there is a design fault that creates this scenario.

Because of this I have not replaced the switch and as I am now aware of the problem and its symptoms I deal with it when it rarely occurs, 4 times in 10000 miles in my case.

To remove the switch it requires the removal of the panels below the steering wheel above the drivers footwell ,the screws and fastenings are all relative to each panel and garnish and great care is needed in remembering where everything fits back together,to make things easier it is better to remove the cowl around the steering wheel as this gives better line of sight to the area you are aiming to expose.

The switch fits on to the end of the ignition barrel and is held in place with a screw ,the ignition wiring plugs into the switch body.

Good luck with the job, the switch is available from Lexus and is also available on the web from other sources and cheaper than Lexus.

Mike Scott · August 14, 2015

Many thanks for your reply, all is a little clearer now. In order to remember where & how everything fits back together I'll probably take photos as I progress.