Ls400 speedometer trouble

[Kathaar]

So, this is my first car, it's as old as I am, but when I bought it, the speedo sagged below the 0mph line, and would operate normally, just completely off kilter (saying i'm at 25mph when i'm anywhere between 40-50, etc) the Odo, fuel gauge, temp, everything else seems to work normally. Yesterday, I finally took it to a dealer to get a diagnostic on what might be causing the issue (since it could be many things) the guy told me since it was only the speedo they'd have to send the entire system out to be fixed (a $1k fix. no thanks.) but he said another mechanic who owns the same car has found that hitting the top of the dash fixes it. so, on the way home, I tried it.

 

NOW the speedo doesn't work at all, if I hit about 50 I get a little bit of wiggle but the needle is almost completely hanging vertically on my dash. So, whatever I did, it seems to have completely disengaged it (everything else still works fine)

 

So, i'm about ready to jump in there, tear everything out, and fix it myself but, I have no idea where to even start, and even still there's no gauruntee i'll even find the problem. Long story short; I need help. Does anyone have any idea what might be causing this? where to look? and how to approach the problem?

[billydpowell]

sure, go to lexls.com and start reading and you will be as smart as the rest of us...

http://www.lexls.com/  from 1990-1997, this sis our "bible" so very much information is here..

[Kathaar]

You are amazing. thank you.

[Kathaar]

Okay so after some studying, I know how to dismantle the dash, but... in terms of the speedo not working, i still don't know what to look for.

[Exhaustgases]

The cheap and easy fix is to contact Tanin auto electric. They do good work and for whats involved to do it, they almost work for free.

[Kathaar]

Well, I completely took the console apart and got stuck at the electric motors that run the speedo and rpm meters. I've put it all aside for now but does anyone have any theories on what might be the issue? The speedo just feels like it's off set. Like if it were an analog system with gears, it feels like the gears slipped. Before I dismantled it I was toying with the needle and I noticed it would stop at 100mph, but fall far below zero, giving me the impression the default 'range of motion' for the needle has been shifted. There is also a small chance the previous owner might have tried to turn back the odometer, would that cause the speedometer to do this? 

[CELSI0R]

Hi Kathaar,

Congrats on your first car. It's a really good choice, to say the least.

I had the same problem with my tachometer. [It happens over time with these cars] I found this fix on this forum, which worked perfectly for me. 

If you notice that your speedometer needle sits a little below zero or drops below when the car is off, then I'm fairly certain this fix will work for you. :)

This image shows what I am referring to. It could also happen when the car is on:

[Disclaimer: This is not my photo, nor is this my car. This is a 1991 LS400 with a tachometer and speedometer needle that needed calibration]

Here is the text from that post:

 

Quote

okay guys, I am going to give you a very constructive advice on how to fix this problem.

1. First remove the cluster and if you do not know how go to lexls.com and follow the instructions.
2. then remove the face cover .first grasp the tach needle gently and pull until you hear a pop,again be gentle and do not ge scared.
3. once you hear the pop move the needle clockwise until it pops again then gently release it.
4. now move the needle slowly counterclockwise until you sit it over the zero and make sure that it sits right on the zero.
5. to check your work move it gently say to the 3k RPM mark  then let go it should snap right back to zero,once you have accomplished this ,you are rock & roll baby. the same thing goes for speedometer.

... this job should take about an hour if you how to handle things. Good luck and let me know. 
please make a donation to lexls.com, this guy is great.may god bless his soul.

 

Here is ramnozack's profile, to cite a source.

[billydpowell]

14 hours ago, CELSI0R said:

okay guys, I am going to give you a very constructive advice on how to fix this problem.

1. First remove the cluster and if you do not know how go to lexls.com and follow the instructions.
2. then remove the face cover .first grap the tach needle gently and pull untill you hear a pop,again be gentle and do not ge scared.
3. once you hear the pop move the needle clockwise untill it pops again then gently release it.
4. now move the needle slowly counterclock till you sit it over the zero an on the dot and make sure that it sits right on the zero.
5. to check your work move it gently say to the mark 3 then let go it should snap right back to zero,once you have accomplished this ,you are rock & roll baby. the same thing goes for speedometer.

 

... this job should take about an hour if you how to handle things. Good luck and let me know. 
please make a donation to lexls.com, this guy is great.may god bless his soul.

This is very good information PD, put it in a stickey for everyone...

[CELSI0R]

14 minutes ago, billydpowell said:

This is very good information PD, put it in a stickey for everyone...

Thanks, Billy. I definitely agree with you.

I intend to add it to the How To Guides section of this forum, but I keep getting errors when I go to the tutorial page. Maybe I just need to reach a certain quota of posts.. I'm still getting familiar with this forum.

In any case, I want to make sure that  ramnozack gets credit for writing the original tutorial, as I only changed the formatting to make it easier to read. The image would also be good to provide a visual for viewers.