# 1998 Astro fuel gauge problem



## 5353456 (Apr 19, 2007)

Has anyone experienced the gas gauge moving erratically, looks like its pulsing/vibrating. Also when engine is first started the the gauge swings past the full then settles down. This vibrations is also visible with the key in the on position with the engine not started. any help with this would be greatly appreciated.


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## Midnight Tech (Dec 31, 2001)

I've seen this on many GM products...the gauge will pulse with any electrical load that switches on and off like signals, wipers, etc. The vibrations before its cranked are probably coming from the fuel pump running.
Our delivery truck and the wife's Cobalt cycles to full before coming back to show the actual reading.


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## pt121984 (Mar 21, 2007)

The swing of the gauge is quite normal on these vehicles. As far as the erratic behavior, that could be any number of things. Does it do it at any specific point of how full the tank is? Does it just do it all the time regardless how much is in the tank? Does it only do it when it is running or any time the key is on? If it is only doing it when running, try disconnecting the regulator wire on the Alternator and starting it up and see if it still does it.

Patrick

P.S. Didn't know these Auto boards were here. I spent 15 years as a General Tech. Worked for Firestone and Western Auto, now I'm an Assistant MG at an Auto Parts store. Was really tired of oweing the Snap-On man 1/3 of my weekly salary. :grin:


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## 5353456 (Apr 19, 2007)

Thanks for the feedback, I have taken note and it doesn't matter at what level the tank is at it behaves the same. There is also a humming sound that appears to be coming from the dash area. This does occur though even if the engine is not running with the key in the acc. position. You are correct about the gauge swinging to max full then settling down.


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## pt121984 (Mar 21, 2007)

Are you sure the humming is not coming from the blower motor? Keep in mind that it still runs slowly even if it is turned off as long has the key is on that is. THe best way to check is to pull the hot wire off the blower motor to see if the humminng stops unless you know right where the fuse is.

Also, the sender may be at fault. And I've heard....not positive on this one, that the Gauges are liquid filled and will humm when the liquid leaks out.

Patrick


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## 5353456 (Apr 19, 2007)

Yes I did have the blower motor in the off position. This is a real odd fault the needle swings way to the full then bounces back vibrates for a while then settles down. I turn the engine off turn the gauges on to see what it's up to and it's bouncing around. 
I believe that the sending unit in electrically connected to the ecm and the ecm then sends a voltage to the meter that displays the level. I'm thinking that there may be some kind of electrical connection fault somewhere. 
Thanks again.


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