Author Topic: Attn: car repair gurus - speedometer going nuts  (Read 5583 times)

Offline ladieu

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Attn: car repair gurus - speedometer going nuts
« on: August 02, 2010, 06:58:27 AM »
So in my quest to be more self reliant I want to see if I can fix my vehicle. I have never attempted to fix anything on my car beyond a simple oil change.

it is a 95' Chevy Astro with AWD

All has been smooth sailing for over a year. All of a sudden yesterday when I went to go somewhere the battery was dead. OK no biggie, I jump it and it fires right up.  I start driving again the speedometer is going completely bonkers... it is pegged at over 100MPH and then back down to 15MPH and then pegged again, etc.

So I pull over and it let it sit for awhile.  I then decide I will turn it on/off to see if that fixes it (hell rebooting solves 90% of tech support requests!)

Of course battery is dead again so I jump it again and take the thing home. Transmission seems to shift normally even though the speedometer is going nuts.

So I was going to replace the battery tonight, however I was wondering if anyone had any tips for me regarding this problem.

-Nick
 

Offline fritz_monroe

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #1 on: August 02, 2010, 07:09:39 AM »
Only car I've experienced that problem with was a 1982 Pontiac Grand Prix.  That one was a speedometer cable.  But I'm sure that your Astro has far more computer controlled items than that Grand Prix.

Good luck with it and let us know what you end up doing.  And anything more complicated than changing out a battery, I'd love to see pics.

Offline ladieu

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #2 on: August 02, 2010, 07:17:13 AM »
Yes reading online that cable replacement is where to start, from there go to sensor... I'll give it a go. I need to use it this weekend, so if I can't get it sorted by wednesday it is going to the shop  :-\

Offline ladieu

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #3 on: August 02, 2010, 07:34:42 PM »
ok so replacing the battery fixed all my problems... i guess i just didn't realize that having a bad battery would make the speedometer freak out :D

-Nick

Offline ncjeeper

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #4 on: August 02, 2010, 09:38:02 PM »
I was going to say to check the sensor at the tranny first, but obviously it wasn't getting enough voltage to operate properly.

Offline Ian-FW

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #5 on: August 13, 2010, 05:46:47 AM »
I had the same thing happen to a 95 S10 pickup. My battery started to die, and the first symptom was all the gauges going wonky like that. Replaced the battery, and everything went back to normal.

Offline Zef_66

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #6 on: August 13, 2010, 02:40:36 PM »
Glad you got everything fixed. But make sure to check your terminals and cables for corrosion. If left go long enough, it can cause issues like this. And many times people will replace the battery when it really isn't the problem. And in the process of changing the battery, the corrosion is cleaned up, so they are none the wiser.

Offline ladieu

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #7 on: August 16, 2010, 07:05:58 AM »
hey thanks for the tip.

I cleaned everything with a wire brush and baking soda/water mixture... I didn't see much corrosion... but decided to do it anyway. Rubbed everything down with petroleum jelly before hooking up the new battery...

Oh just as a side note... the battery was actually not the issue as the alternator was bad.  I'm not sorry I got the new battery though, the one I had in was on it's way out anyway... (though not 100% bad)

-Nick

Offline drag0nk1ng

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #8 on: August 19, 2010, 08:42:33 PM »
Just another thing. Not sure how long ago you put the new battery in. But you need to ensure you have the charging system tested. I have been a Tech for 18 years and have seen many cars come in wanting just a battery  and nothing else. Leave the shop thinking everything was fine and then end up coming back into the shop on a hook (tow truck). A new battery can be capable of running the vehicle on its own for sometime, depending on the application, a week or more. It only takes a couple minutes and a lot of parts stores do it for free now.

It is worth the piece of mind knowing that the charging system is good to go.

P.S. The cause of the symptom is the low voltage causing relays to lose contact and cycle on and off. This can be dangerous for the electronics too as it can cause spikes that can wreak havoc on the delicate components.

Offline ladieu

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #9 on: August 20, 2010, 06:27:57 AM »
Hey thanks for the feedback, yeah thank god I have the remote jump start thingy to charge the dead battery. Bad alternator ended up being the thing.

-Nick

Offline donaldj

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #10 on: August 20, 2010, 06:54:10 AM »
I would get a GPS with a speed readout involved. This way we can be sure you're not just driving very, very erratically.    ;D

Offline “Mark”

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Re: Attn: car repair gurus - speedometer going nuts
« Reply #11 on: September 09, 2010, 11:14:39 AM »
I realize the cause has already been determined, but wacky gauges often mean a bad alternator. Chevy alternators need to be replaced reasonably frequently, as the back bearing is undersized and wears out quickly. My mom had the exact same thing happen in a 91 Corsica. That car went through at least 2  alternators while she had it.