Car Speedo Question

[John Smyth]

My AE82 Corolla (1985) has an annoying problem with the speedo needle
vibrating (and making a ticking sound) at certain speeds.

I was curious if maybe there is a capacitor (used to smooth out some kind of
speed pulses) which has dried out?

Is that how they work?

John

 

[Gordon W]

John Smyth <smyth@tpg.com.au> wrote in message
news:4130e3dc@dnews.tpgi.com.au...

My AE82 Corolla (1985) has an annoying problem with the speedo needle
vibrating (and making a ticking sound) at certain speeds.

I was curious if maybe there is a capacitor (used to smooth out some kind
of
speed pulses) which has dried out?

Is that how they work?

John


The problem with my 92 Camry was too much end play in the magnetic drum on

the shaft to the needle. Taking out the end play by pushing the drum back
fixed the vibrating and the ticking. Don't think I described that very well


Gordon

 

[Franc Zabkar]

On Sun, 29 Aug 2004 06:05:17 +1000, "John Smyth" <smyth@tpg.com.au>
put finger to keyboard and composed:

My AE82 Corolla (1985) has an annoying problem with the speedo needle
vibrating (and making a ticking sound) at certain speeds.

If it uses a mechanical speedo cable, then it probably needs to be
cleaned and lubricated.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Roger Lascelles]

In a mechanical speedo, a circular magnet rotates inside an alumimium drum.
Currents flowing in the drum, drag the drum in the same direction as the
magnet. The speedo pointer is attached to the drum and a spiral spring
attached to the drum balances force due to rotational speed.

The magnet to drum clearance is quite small, so that bearing wear, warping
of the structure, or attraction of iron filings to the maganet, can cause
contact at some point in each revolution. At each contact, the drum gets a
"flick", causing the speedo needle to jump.

If you open the speedo, you may be able to find the problem.

Roger


"John Smyth" <smyth@tpg.com.au> wrote in message
news:4130e3dc@dnews.tpgi.com.au...

My AE82 Corolla (1985) has an annoying problem with the speedo needle
vibrating (and making a ticking sound) at certain speeds.

I was curious if maybe there is a capacitor (used to smooth out some kind
of
speed pulses) which has dried out?

Is that how they work?

John

 

[budgie]

On Sun, 29 Aug 2004 06:05:17 +1000, "John Smyth" <smyth@tpg.com.au> wrote:

My AE82 Corolla (1985) has an annoying problem with the speedo needle
vibrating (and making a ticking sound) at certain speeds.

I was curious if maybe there is a capacitor (used to smooth out some kind of
speed pulses) which has dried out?

Nope

Is that how they work?

Nope. It is a cable drive and an induction cup coupling to the needle. By far
the most likely cause is a kink in the cable or the transmission fitting isn't
snug, OR the end on the cable (usually the transmission end) is wearing.

 

[John Crighton]

On Sun, 29 Aug 2004 14:52:13 +0800, budgie <me@privacy.net> wrote:

OR the end on the cable (usually the transmission end) is wearing.

LOL
I have just been down that path with my son's old KE70 corolla.
The worn plastic gear wheel that drives the speedo cable was
replaced and it lasted a few months before it became all chewed
up also.

Searched for another 4 speed gearbox at the wreckers. Found
a 5 speed gearbox with its small nylon speedo drive gear looking
good. There was a nice engine attached to this nice gearbox.
Pity to separate!
So we bought the lot and did an engine plus gearbox transplant.

Little jobs sometimes blow out to larger jobs in old cars.

Regards,
John Crighton
Hornsby

 

[mark krawczuk]

hi, u sure its a electronic speedo ?
i am pretty sure that they are a mechanical driven.
see if there is a speedo cable coming out the gearbox and going right
behind the speedo.
mark k

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"John Smyth" <smyth@tpg.com.au> wrote in message
news:4130e3dc@dnews.tpgi.com.au...

My AE82 Corolla (1985) has an annoying problem with the speedo needle
vibrating (and making a ticking sound) at certain speeds.

I was curious if maybe there is a capacitor (used to smooth out some kind
of
speed pulses) which has dried out?

Is that how they work?

John

 

[Dean]

"Roger Lascelles" <rogerlasAToptusnet.com.au> wrote in message
news:41315faa$0$9811$afc38c87@news.optusnet.com.au...

In a mechanical speedo, a circular magnet rotates inside an alumimium
drum.
Currents flowing in the drum, drag the drum in the same direction as the
magnet. The speedo pointer is attached to the drum and a spiral spring
attached to the drum balances force due to rotational speed.

The magnet to drum clearance is quite small, so that bearing wear, warping
of the structure, or attraction of iron filings to the maganet, can cause
contact at some point in each revolution. At each contact, the drum gets
a
"flick", causing the speedo needle to jump.

If you open the speedo, you may be able to find the problem.

Roger

It sounds like a worn flexible cable that usually runs from your gearbox
output up to the instrument housing in your dashboard. If these cables are
forced to go through a sharp bend, thats usually where they go first. The
clicking sound might be caused by some of the windings used to make up the
flexible cable having come unwound and rubbing against the cable housing.
Try not to take the speedo apart down as far as the magnet assembly is
concerned because you can accidently demagnetise it slightly and lose your
calibration. You can check if the flexible cable is buggered by taking it
out and holding one end of the inner cable while twisting the other. It
should not have more than about an eighth of a turn ' flex ' in it for the
average length cable ( say about 1.5 to 2 metres ).

Dean.