All Gauges "jumping" at Times when Car is Off. - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 13 (permalink) Old 07-16-2012, 10:07 AM Thread Starter
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All Gauges "jumping" at Times when Car is Off.

Hello. I have these strange thing happening. Sometimes but not all the time after turning the car completely off after driving, all three of my gauges (gas, speedometer, and rpm gauge) briefly move or jump. They dont move alot they almost wiggle (example if i was looking at the gas gauge the needle would slightly jump to the first line then back down). Im concerned thisis an electrical issue. I drive a 2009 cobalt LS Sedan purchased brand new july 2009 (which sucks because bumper to bumper is about to expire this week) please help.
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post #2 of 13 (permalink) Old 07-16-2012, 10:33 AM
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Probably just counter emf from radiator fan motors as they turn off. Try turning the ignition on but not starting the car, if it still does it my theory is shot down. But if my theory is right it should only do this when the radiator fans are running upon shutting down the car. So next time try noticing if fans were running just before your needles wiggle. This should be harmless by the way, but GM did add a bypass counter EMF diode at one point but only on low speed fan.

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post #3 of 13 (permalink) Old 07-16-2012, 10:33 AM
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I have the same issue in my 2008 G5 Coupe. Its odd. Hopefully someone here can help.

Edit: Coby, Ill try the same thing.
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post #4 of 13 (permalink) Old 07-16-2012, 10:38 AM
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Its normal. Its the needles resetting from their 'ready position' They should rest about .25"-.5" below the 0 lines on all the gauges, then when you turn on the ignition (car doesn't need to be started) the needle motors energize and they sit at 0. You should notice this happen every time you turn the ignition off after about 30 seconds. Theyll twitch for about 3-5 seconds then drop below the 0 lines.

Its an easy way to reset them manually if you do anything to the cluster like LED swap or change the overlay.
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post #5 of 13 (permalink) Old 07-16-2012, 10:58 AM
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EMF stands for ElectroMagnetic Field. And needles reset when you turn cluster on not off.


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post #6 of 13 (permalink) Old 07-16-2012, 12:16 PM
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resetting isnt the word I should be using, its more like the motors that drive them are discharging theyre power and going to a resting position.
This twitching happens regardless of the engine running or not so I doubt the engine cooling fan will be effecting/causing it.
And it shouldnt be intermittent, it should happen every time the ignition cycles (if you give it enough time)
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post #7 of 13 (permalink) Old 07-16-2012, 12:33 PM
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I have this same prob and occurs occassionally. I think it has somthing to do with a ground cause my bat cuts out and the comes back on and everything is reset but my bat...alt...and starter are fine it weird

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post #8 of 13 (permalink) Old 07-16-2012, 12:35 PM
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Quote:
Originally Posted by jerseycobalt View Post
I have this same prob and occurs occassionally. I think it has somthing to do with a ground cause my bat cuts out and the comes back on and everything is reset but my bat...alt...and starter are fine it weird
next time youre in the car, turn it on, turn it off, remove keys, and watch the needles. They should twitch after about 30 seconds....is that what youre referring to?
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post #9 of 13 (permalink) Old 07-16-2012, 01:28 PM
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Quote:
Originally Posted by acoutu View Post
next time youre in the car, turn it on, turn it off, remove keys, and watch the needles. They should twitch after about 30 seconds....is that what youre referring to?
Only if you open the doors, otherwise it should stay at "0" until radio shuts off at the end of "RAP".

Acoutu, I think we are talking about two different events. The OP is suggesting that his needles go up as far as the first line on fuel gauge when he turns his car "off" and the event your referring to is when RAP shuts "off" and the needles all go to their mechanical resting stops.

Snappa, I wouldn't worry about it, both these conditions are normal.

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post #10 of 13 (permalink) Old 07-16-2012, 03:54 PM
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I've only every tried this with the doors open actually so RAP would already be off so that would make sense.
It sounds like we are talking about the same thing. The 'twitching' I'm referring to includes the needles bouncing up and down for about 3 seconds. They move about 1/4" so the first line on the gas gauge would be about right.

Like you said though, its normal.
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