Subject: [TR] TR3 Speedometer

From: [email-masked]
Date: Thu, 2 Jul 2015 22:55:18 +0000 (UTC)

The speedometer on my TR3 stopped working.  First the odometer quit and the mph needle fluctuated randomly.  Then the needle fell off altogether.  

Just taking a leap here, I'm assuming that means it doesn't work anymore.  

So, I've replaced all four of the smaller two inch gauges with SunPro.  Is there an aftermarket speedometer, maybe matching tach, that works with our cars?

I'm not interested in the finery of fixing the internals of a TR3 speedometer.  I'm just not good enough or have steady enough hands. 

Terry Smith, '59 TR3A
New Hampshire

** [email-masked] **

Archive: http://www.team.net/archive

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From: George Richardson <[email-masked]>
Date: Thu, 02 Jul 2015 19:11:18 -0400

Had this happen with my Tach. I replaced it with one from ebay and am 
going to send it out for repair.

George Richardson
Key Men - Keys for Classics
www.key-men.com

1957 Triumph TR3
1961 Jaguar Mark 2
1975 Triumph TR6
1997 Land Rover Discovery

On 7/2/2015 6:55 PM, [email-masked] wrote:
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From: Frank Fisher <[email-masked]>
Date: Thu, 2 Jul 2015 23:21:34 +0000 (UTC)

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as alwaysthanks
      From: Randall <[email-masked]>
 To: 'Frank Fisher' <[email-masked]>; 'Triumphs List' <triumphs@autox.=
team.net>=20
 Sent: Thursday, July 2, 2015 3:25 PM
 Subject: RE: [TR] gas gauge and voltage regulators
  =20
>=C2=A0 the purpose of the voltage regulator is to stop the ups and=20
> downs of the voltage caused by alternator as engine revs?=20

Yes.=C2=A0 At idle, the stock Lucas alternator (or generator on the TR4/4A)=
 puts out almost nothing, so the battery voltage can droop
quite a bit under heavy load (eg headlights on).=C2=A0 The gauges used on T=
R4-6 work on heat, and so are very sensitive to changes in
voltage (power and therefore heat is related to the square of the voltage).

> what then is usual output? ie 13/14 volts in----? volts out.

The stock "voltage stabilizer" doesn't actually change the voltage.=C2=A0 I=
nstead, it interrupts the voltage output part of the time,
such that the average is 10 volts.=C2=A0 The technique is commonly known as=
 Pulse Width Modulation (PWM) and is still quite common today.
But, modern devices use solid state switches (transistors) that can switch =
very quickly.=C2=A0 Transistors back then were expensive and
fragile, so Smiths (or whoever owned them by then) used a simple mechanical=
 switch that only operated a few times per second.
Pretty ingenious really, but like so many other things on our cars, strange=
 and poorly understood today.

Since the gauges are so slow to respond, they don't follow the constant up =
and down from the VS, but any voltmeter or DMM will.=C2=A0 So,
it's more or less impossible to check the original VS accuracy with a voltm=
eter or DMM.=C2=A0 Smiths' suggestion was to hook up a "known
good" gauge along with a dash light bulb in series to a regulated 10v sourc=
e, note the resulting reading, then hook it up to the VS
to be tested and compare the reading (after waiting for it to settle each t=
ime).

But in my limited experience, the usual VS failure modes are either that th=
e heater burns out (meaning it supplies input voltage all
the time), or the contacts go bad.=C2=A0 You can check the contact resistan=
ce with an ohmmeter.=C2=A0 Or just pull the wire off the
temperature sender and connect it to a test lamp (with the other side of th=
e lamp grounded).=C2=A0 If you can see the light blink on and
off, the VS is working, and probably reasonably accurate.=C2=A0 Unless you =
are chasing a fairly subtle error in gauge reading, the
problem is not the VS.

> any one have a list of what smiths gauges require a voltage=20
> stabilizer and those that don't. have not been to see the car=20
> yet, but id like to be prepared.

Sorry.=C2=A0 I had a partial list, but can't seem to find it at the moment.=
=C2=A0 But all of the fuel and temperature gauges originally used
on TR4-TR6 (as well as Stag, 2000 and so on) require a VS.=C2=A0=20

-- Randall=C2=A0=20

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<html><body><div style=3D"color:#000; background-color:#fff; font-family:He=
lveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;fo=
nt-size:16px"><div dir=3D"ltr"><span>as always</span></div><div dir=3D"ltr"=
><span>thanks</span></div><br>  <div style=3D"font-family: HelveticaNeue, H=
elvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px=
;" id=3D"yui_3_16_0_1_1435879145015_4115"> <div style=3D"font-family: Helve=
ticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font=
-size: 16px;" id=3D"yui_3_16_0_1_1435879145015_4114"> <div dir=3D"ltr"> <hr=
 size=3D"1">  <font size=3D"2" face=3D"Arial"> <b><span style=3D"font-weigh=
t:bold;">From:</span></b> Randall &lt;[email-masked]&gt;<br> <b><span =
style=3D"font-weight: bold;">To:</span></b> 'Frank Fisher' &lt;yellowtr3@ya=
hoo.com&gt;; 'Triumphs List' &lt;[email-masked]&gt; <br> <b><span =
style=3D"font-weight: bold;">Sent:</span></b> Thursday, July 2, 2015 3:25 P=
M<br> <b><span style=3D"font-weight: bold;">Subject:</span></b> RE: [TR] ga=
s gauge and voltage regulators<br> </font> </div> <div class=3D"y_msg_conta=
iner" id=3D"yui_3_16_0_1_1435879145015_4113"><br>&gt;&nbsp; the purpose of =
the voltage regulator is to stop the ups and <br clear=3D"none">&gt; downs =
of the voltage caused by alternator as engine revs? <br clear=3D"none"><br =
clear=3D"none">Yes.&nbsp; At idle, the stock Lucas alternator (or generator=
 on the TR4/4A) puts out almost nothing, so the battery voltage can droop<b=
r clear=3D"none">quite a bit under heavy load (eg headlights on).&nbsp; The=
 gauges used on TR4-6 work on heat, and so are very sensitive to changes in=
<br clear=3D"none">voltage (power and therefore heat is related to the squa=
re of the voltage).<br clear=3D"none"><br clear=3D"none">&gt; what then is =
usual output? ie 13/14 volts in----? volts out.<br clear=3D"none"><br clear=
=3D"none">The stock "voltage stabilizer" doesn't actually change the voltag=
e.&nbsp; Instead, it interrupts the voltage output part of the time,<br cle=
ar=3D"none">such that the average is 10 volts.&nbsp; The technique is commo=
nly known as Pulse Width Modulation (PWM) and is still quite common today.<=
br clear=3D"none">But, modern devices use solid state switches (transistors=
) that can switch very quickly.&nbsp; Transistors back then were expensive =
and<br clear=3D"none">fragile, so Smiths (or whoever owned them by then) us=
ed a simple mechanical switch that only operated a few times per second.<br=
 clear=3D"none">Pretty ingenious really, but like so many other things on o=
ur cars, strange and poorly understood today.<br clear=3D"none"><br clear=
=3D"none">Since the gauges are so slow to respond, they don't follow the co=
nstant up and down from the VS, but any voltmeter or DMM will.&nbsp; So,<br=
 clear=3D"none">it's more or less impossible to check the original VS accur=
acy with a voltmeter or DMM.&nbsp; Smiths' suggestion was to hook up a "kno=
wn<br clear=3D"none">good" gauge along with a dash light bulb in series to =
a regulated 10v source, note the resulting reading, then hook it up to the =
VS<br clear=3D"none">to be tested and compare the reading (after waiting fo=
r it to settle each time).<br clear=3D"none"><br clear=3D"none">But in my l=
imited experience, the usual VS failure modes are either that the heater bu=
rns out (meaning it supplies input voltage all<br clear=3D"none">the time),=
 or the contacts go bad.&nbsp; You can check the contact resistance with an=
 ohmmeter.&nbsp; Or just pull the wire off the<br clear=3D"none">temperatur=
e sender and connect it to a test lamp (with the other side of the lamp gro=
unded).&nbsp; If you can see the light blink on and<br clear=3D"none">off, =
the VS is working, and probably reasonably accurate.&nbsp; Unless you are c=
hasing a fairly subtle error in gauge reading, the<br clear=3D"none">proble=
m is not the VS.<div class=3D"qtdSeparateBR"><br><br></div><div class=3D"yq=
t8541498650" id=3D"yqtfd19863"><br clear=3D"none"><br clear=3D"none">&gt; a=
ny one have a list of what smiths gauges require a voltage <br clear=3D"non=
e">&gt; stabilizer and those that don't. have not been to see the car <br c=
lear=3D"none">&gt; yet, but id like to be prepared.</div><br clear=3D"none"=
><br clear=3D"none">Sorry.&nbsp; I had a partial list, but can't seem to fi=
nd it at the moment.&nbsp; But all of the fuel and temperature gauges origi=
nally used<br clear=3D"none">on TR4-TR6 (as well as Stag, 2000 and so on) r=
equire a VS.&nbsp; <br clear=3D"none"><br clear=3D"none">-- Randall&nbsp; <=
div class=3D"yqt8541498650" id=3D"yqtfd52573"><br clear=3D"none"><br clear=
=3D"none"></div><br><br></div> </div> </div>  </div></body></html>
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