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From: tmorris@convex.UUCP
Newsgroups: net.auto
Subject: Re: Speedometer weirdness
Message-ID: <82600008@convex>
Date: Tue, 3-Sep-85 14:39:00 EDT
Article-I.D.: convex.82600008
Posted: Tue Sep  3 14:39:00 1985
Date-Received: Fri, 6-Sep-85 03:30:17 EDT
References: <1402@umcp-cs.UUCP>
Lines: 64
Nf-ID: #R:umcp-cs.UUCP:-140200:convex:82600008:000:2520
Nf-From: convex.UUCP!tmorris    Sep  3 13:39:00 1985


	If you were going to have to work on a speedo on any vehicle,
(of modern manufacture) you couldn't get an easier one than a chevette.
It is quite easy to remove and repair , and if you aren't afraid ,have
a blast and save bucks.
	You asked how it works. The cable is connected ,thru a bearing
and shaft arrangement ,to a magnet . This causes the magnet to rotate
in proportion to the vehicle speed . Surrounding the magnet is a steel
shell , which is on another shaft connected to the needle. there is a 
very fine spring around this shaft that attepts to pull the needle
towards zero by rotating the needle shaft counterclockwise. The magnet,
spinning clockwise opposes the action of the spring , and the balance
between these forces causes the needle to indicate your speed.
	Now , what is wrong with yours ?
POSSIBILITIES :	

	1. Bent needle shaft . There is an emission service required on 81 and later chevettes in which a yellow indicator on the odometer
is reset. The needle or needle shaft can get bent at this time....
ask me how I know...

	2. Bent speedo faceplate . They are very thin , and almost any
under-dash activity which involves pulling on the speedo cable to get it
out of the way can bend it.

	3. Grease from the speedo cable slinging out into the magnet
shell. From excessive lubrication of speedo cable at wrong points.

	4. Bad needle shaft bearing.

	5. Rust in magnet shell

	6. Worn bushing.

WHAT ARE YOU GONNA DO ?
        
	SUGGESTIONS:

	1. If you elect to remove the speedo head yourself , put in
	fresh cable while you're there.

	2. If you dont see anything real obviosly wrong , take the 
	removed speedo to a speedo shop. They don't charge nearly as
	much when the units are brought in minus the car. Also they
	can calibrate it for you.

	3. Before you even pull it out , see if reaching under the
	dash and pushing UP on the speedo cable fixes it. I've seen a
	lot of chevettes fixed that way. If it goes away when pushed up
	, use a  ty-wrap to hold it in place.

	4. If you have an 81 or later model , there will be a sensor
	on the back of the speedo head with a couple of wires on it.
	Remove the entire sensor by taking out the 1/4 " hex - head
	screw. Be sure to hook it back up , it tells the computer
	how fast you're going , and if you forget , the check-engine
	lite will tell on you.

	5. If you replace the speedo cable ,be SURE to rout it like
	the original. They like to get in fights with the wiper
	mechanism....

	                           HAPPY MOTORING !
.