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Tachometer being dumb

Tachometer being dumb

Postby Skeith [OP] » Mar 22 2013, 2:09pm

yesterday on my way home from work, near the end of my 20 min drive, I noticed my tach was reading high.
I accellerated and it peaked 4k. Thought to myself. I didn't push it that hard.
So i killed the radio to listen to the motor and indeed it was operating at the proper RPM, tach was reading high.

Got home and parked it. Shut off the ignition and the needle dropped to 1.5k and stuck.
Kinda messed with it a bit and it is definately reading 1.5k too high. The tach shows about 2k idle which is right for 500-600 RPM over 1.5k. Engine sounds fine, definately not idling high.

Shut it off and went inside.
Later that night, decided to try it again when I went out for a smoke. Needle was sitting at 1k, and now reading 1k over actual.

This morning on the way to work, it was sitting at 500 RPM over actual.

Will have to see what it does after work.

Is this a common problem? Do I have to worry about full cluster failure. Everything else seems to be working properly. Spedometer is working, fuel and temp guages are working. Odometer and trip counters working fine.

Probably call my dealer this weekend.
Just wondering if this is common or not?
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Tachometer being dumb

Postby Machster69 » Mar 22 2013, 3:12pm

Hm! Cant say I have seen one fail in a nnbs yet? Ide suspect the cluster, but let us know what you find.
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Re: Tachometer being dumb

Postby Joseph » Mar 22 2013, 3:30pm

There should be a little step motor behind the tachometer gauge. These can go bad. If you are good at soldering you can replace it by yourself in less than 30 minutes.
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Re: Tachometer being dumb

Postby Skeith [OP] » Mar 22 2013, 3:36pm

Soldering is not a problem for me. I have done surface mount ICs with a pencil Iron.

Just came back from a smoke break, Its now sitting 250RPM over. Slowly going back.

I have a feeling its the stepper because when it drops after reving the engine, it kinda moves jerky for the last 1/8" or so of travel.
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Tachometer being dumb

Postby Machster69 » Mar 22 2013, 3:57pm

We have a How To for replacing them, but like I said... This might be the first 2009 ive seen the motors fail...
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Re: Tachometer being dumb

Postby Skeith [OP] » Mar 22 2013, 6:43pm

took a look at the how to guide. Looks pretty straight forward.

Went for lunch, got in the truck, tach needle was BELOW zero. Turned the ignition to run and the needle poped up to zero.
Tach worked fine on my drive to grab a burger and fries, shut it off and it dropped to zero just like it should.

Thing is just loopy.

Maybe it was having a bad day, heh Ill keep and eye on it and see what happens.
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Re: Tachometer being dumb

Postby todd101 » Mar 22 2013, 7:09pm

Mine did the opposite. It was reading 500rpms too low. I shut the truck off and when I restarted it, everything was fine. That was 8 months ago and it hasn't done it since.
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Re: Tachometer being dumb

Postby Skeith [OP] » Mar 22 2013, 7:22pm

Might pull my oscilloscope into the garage this weekend and scope the vehicles power system and see how noisy it is.
I have heard that noise on the line can cause the guages to get weird. Though I would have figured I would have heard it through my CB speaker.
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Re: Tachometer being dumb

Postby Mattymay » Feb 09 2017, 1:07am

Hi Skeith. I'm having the same problems with my gauge on my 2012 Silverado. It sits at about 2000 off. And spikes pretty high while driving. (About 2000 over) I was just wondering if you ever resolved your problem and if so how you did it?
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