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Re: Dash Light Rheostat

To: Malcolm Walker <walker05@camosun.bc.ca>, DANMAS@aol.com
Subject: Re: Dash Light Rheostat
From: Trevor Jordan <trevor.jordan@rmit.edu.au>
Date: Mon, 13 Oct 1997 15:13:37 +1000
Cc: smith007@ix.netcom.com, triumphs@Autox.Team.Net
References: <971012222926_-1395183060@emout17.mail.aol.com>
At 14:01 +1000 13/10/97, Malcolm Walker wrote:
[Dan Massey]
>> For my two cents worth, I wouldn't waste the money. The dash lights are
>> barely usable as it is, even with the dimmer set to the brightest
>>setting. If
>> it were me, I would just jumper the rheostat out, and leave the knob in
>>place
>> just for apearance sake.
>
>When I had a late job a couple of summers ago I drove a god-awful Ford
>Fairmont wagon.  I found that night driving was much easier when the
>gauges could be dimmed.  However, I'd bet my lousy Ford display was a lot
>brighter than the average TR display.
>
My vote is with Dan Massey.  The TR6 dash lighting seems to have been
designed for dim and dimmer.  At the first opportunity, I intend to bypass
the rheostat.  If I am blinded by the glare, I will make suitable
adjustments.

However, if it is necessary to dim the dash lights, then why not fit a two
position rotary switch (three position if you also want to turn the lights
fully off) with a fixed resistor in place of the rheostat and use the
original knob.  This should cost 10 to 20% of the price of a replacement
Lucas rheostat and should not wear out as quickly.

An earlier email suggested a fixed resistor of about 200 Ohm to dim the
lights.  This seems a bit high.  The normal dashboard lighting current
should be around 1.6 Amp, so 0.2 to 0.4 Amp should provide a usable dim.
This will require a resistance of 30 to 50 Ohm.  Has anyone found the
optimum value by experiment?

The resistor will dissipate around 10 to 12 W and should be given plenty of
space and ventilation.

Trevor Jordan
74 TR6 CF29281U



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