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Tach Not Working


ls40093

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I recently purchased a 1993 LS400 with 92K miles. The car has been maintained by Lexus and I have all the service records. Since getting the car, the tach has gone from sometimes not working when the car is cold to not working at all. The lights on the needle are fine (thank goodness).

I am reluctant to take it to the dealer and am looking for ideas on what to check myself.

Thanks..this forum appears to be a great tool for owners.

ls40093

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I'm interested in hearing about the tach also!

About two weeks ago I noticed the tach needle was only half lit and the tach was very sluggish. Really not going above 2500 rpm at all. The service manual seems to simply say replace it. That's ok if that's the problem, but of course I'm wondering if it could be anything else.

I can't do anything right now as I'm waiting on a fuel pump from Lexus.

Regards,

Mike

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I have a 93 LS that the tach and speedometer were both working intermittently. They would usually not work out of the driveway and would independently start to work whenever the spirit moved them. These gauges share a common ground point and I was convinced that there was a problem with the ground. About a month ago I removed the instrument cluster and very carefully checked everything over for good, clean connections. Snugged all the screws down snug (not overtightening) and then put the cluster back in. Everything worked for about a week then the same problem again. Removed the cluster again and this time fabricated a wire harness to bypass the traces on the flexcircuit board and then carefully resoldered connections on the circuit board ground plane traces. This time the gauges have been working good for about 3 weeks. The tach is actually a very simple circuit in the instrument cluster. You have a signal that comes in from the ignition coil that is routed through a single resistor on the bigger circuit board, power and a ground lead that connect to the meter. I wouldn't mess with these circuit boards unless you are experienced in electronic repair and have the proper equipment. Being ham fisted with a soldering iron on these circuit boards can be disastrous. Good luck,

Curt

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Thanks for the reply. Sounds like a similar problem. My tach has decided to start working again and the speedo has moments when it decides not to function.

I am not brave enough to take on what you did. I'll live with it for a while longer. I would be curious to know if your solution works long term.

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  • 3 months later...
  • 4 months later...

I am having the same problem with the speedometer and tachometer in my LS400. The tach works about 60 percent of the time, while the speedometer works about 10 percent of the time. Does anyone have a solution to this problem?

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I have a 93 LS that the tach and speedometer were both working intermittently. They would usually not work out of the driveway and would independently start to work whenever the spirit moved them. These gauges share a common ground point and I was convinced that there was a problem with the ground. About a month ago I removed the instrument cluster and very carefully checked everything over for good, clean connections. Snugged all the screws down snug (not overtightening) and then put the cluster back in. Everything worked for about a week then the same problem again. Removed the cluster again and this time fabricated a wire harness to bypass the traces on the flexcircuit board and then carefully resoldered connections on the circuit board ground plane traces. This time the gauges have been working good for about 3 weeks. The tach is actually a very simple circuit in the instrument cluster. You have a signal that comes in from the ignition coil that is routed through a single resistor on the bigger circuit board, power and a ground lead that connect to the meter. I wouldn't mess with these circuit boards unless you are experienced in electronic repair and have the proper equipment. Being ham fisted with a soldering iron on these circuit boards can be disastrous. Good luck,

Curt

Curt,

It sounds like you possibly fixed the intermittent tach/speedometer problem. At last report, yours had been working for three straight weeks. Is it still working? Can you give more details on the repair? If possible, please email me directly at: djj6@gte.net.

Thank you!

Dwight

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Hi Curt,

Have a 93 with the same problem. Feel confident I could follow what you did. Could you provide more details and maybe pic's on what you did. This problem is very annoying on a otherwise great car. Laserron@netzero.net.

Thank You,

Ron

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  • 6 months later...
Hi Curt,

Have a 93 with the same problem. Feel confident I could follow what you did. Could you provide more details and maybe pic's on what you did. This problem is very annoying on a otherwise great car. Laserron@netzero.net.

Thank You,

Ron

Hi all,

I also have the same problem. To get the tachs working, I would have to bang on top of the dashboard. I called the lexus dealer and they said it was the instrument cluster that is going bad. They quoted me $1200 for the part and $250 for labor.

Curt,

If you could provide us a step by step procedure on how to fix this problem. I would greatly appreciate it.

Regards,

Jim

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The ebay site listed by Flanker 271 is Jim Walker's. Jim repairs the instrument clusters which will not light up when the weather is cool. He does this by replacing some of the capacitors in the cluster.

Jim worked on my cluster in November, 2003. He fixed the non-lighting problem and also repaired my tachometer and speedometer needles, which were losing illumination. However, these repairs did not fix the inoperative (i.e., failure to move off zero) tachometer and speedometer needles.

I have corresponded with Jim about these problem needles, and he indicated that he was trying to find where the problem lies. I think eventually he will have a fix.

As someone mentioned, rap on the top of the dash just above the instrument cluster. This usually brings my tachometer and speedometer to life.

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