Tach stuck

[eLKuRLy]

I searched and checked almost everything everybody recommended but still tach sticks.

http://www.youtube.com/watch?v=yqvCjFd9O4Q

As you can see from the video, the tach sticks at 2500 rpms. Does not move unless you floor it. Car is an auto, so when I gradually accelerate there is no movement.
-I hit the dash and 'sometimes' it would work, but will get stuck as soon as it reaches 2500 rpms. (needle is not touching the cluster cover)
-checked fuses. all work fine and do not change anything.
-swapped tach w/ working one and still gets stuck at 2500k.
-swapped ecu and still behaved the same.

Don't know what else to check. It's annoying that the tach does not work. Any help will be greatly appreciated.
Thanks in advance.
Carlos

[jlevie]

Have you changed the SI board?

[Todd Black 88]

Yeah, what Jim said.
I had a recent tach issue that was attributed to the si board batteries being low.
Also, above the pedals there is a ground lug that is used by the cluster, pull and clean the terminals and the mount with some sand cloth.

[eLKuRLy]

Have you changed the SI board?

Yeah, what Jim said.
I had a recent tach issue that was attributed to the si board batteries being low.
Also, above the pedals there is a ground lug that is used by the cluster, pull and clean the terminals and the mount with some sand cloth.

Will have to find an SI board to see if that fixes the problem. Meanwhile I will check and clean that ground lug above the pedals.

Thanks guys!!

[e30jr88]

Anyone have a picture of this ground above the pedal?? I'm having issues with my tach as well.. seems it wants to read right but after I let off the gas pedal it just goes down..as if dead but as soon as I get back on the gas pedal works again.. I changed the SI Batts like 3 days ago.

[Gregs///M]

Difficult to take a pic of that area. Just pull your knee bolster off and follow your brake pedal up into the dash. You will notice all the brown wire go to two 10mm nuts on the same bracket. Remove both nuts and clean all ground rings and the grounding stud itself.

Window controls are also grounded here so this fix applies to window slowness, intermittent operation, etc.

For those guys looking for SI batteries, check my sig.

[603Racing]

I had a somewhat similar issue where my tach would not go past 4,100 RPM, ever. Fast or slow rev, banging on the dash or not. Worked fine below that. Turned out to be the plastic gear inside the tach was cracked. Replaced it and it works fine now.

[Gregs///M]

I had a somewhat similar issue where my tach would not go past 4,100 RPM, ever. Fast or slow rev, banging on the dash or not. Worked fine below that. Turned out to be the plastic gear inside the tach was cracked. Replaced it and it works fine now.

Mnn not sure what you mean by plastic gear. Are you sure you're not talking about the Speedometer? Tach has no gears...


Speedo/odometer has several though. Tach readout is controlled via SI board circuitry. Tach movement is solely by motor, no gears.

[603Racing]

The gears are under the face plate...

[brickwhite]

The gears are under the face plate...

no gears huh?

[eLKuRLy]

well, in my case. I switched the tach with a working one and it still gets stuck in the same spot.... still need to swap the si board so see if that's it.

[603Racing]

Yep, not the gears. Old tach is probably still good as well.

[Gregs///M]

Tach signal runs through SI board. I would say it is at fault.

[Spyke]

OP your video is EXACTLY how my tach behaves, only it's stuck at 2k. ^Greg here has already done my SI board, and no improvement. I'm going to try looking for that ground and cleaning it off...

***Edit: Cleaned that ground, no change.

[Gregs///M]

OP your video is EXACTLY how my tach behaves, only it's stuck at 2k. ^Greg here has already done my SI board, and no improvement. I'm going to try looking for that ground and cleaning it off...

***Edit: Cleaned that ground, no change.

For those who messed with their cluster, check the coding plug. Its job is to interpret signal from the DME and translate into something the tach can display.

First check the pins inside the coding plug to make sure they are not bent or misaligned. Second, try swapping with another coding plug.