RE: Dim Instrument Cluster lights

[Paul Lennemann <pjlenn@xxxxxxxxx>]

Robert wrote:
> 
> Bill
> 
> I havent seen behind the instrument cluster in our car so initially I 
> wasnt sure the dimmer was part of he headlamp switch - tho as it's 
> controlled by the same knob, I now realise it would be.
> Then I looked back at some pics we were sent 
> 
> tp://s65.photobucket.com/albums/h233/rob426uk/63%20instrument%20cluster/ 
> 
> (hope the link works?)
> 
> by the people that sold us the spare cluster that we have had sent to 
> Autoinstruments, and saw the headlamp switch looks like the one Jim sent 
> 
> me a link to (thanks Jim!).
> 
> We've had similar problems with our 69 Sport Satellite - that has the 
> separate thumbwheel. Sometimes that takes a few rotations back'n'forth 
> to get the lights to dim/brighten, but they're still pretty dull at the 
> best of times.
> 
> The guy at Autoinstruments offered to test the resistance on the dimmer 
> on the cluster they are restoring, but asked "We can tell if it works 
> but we may not be able to tell if it will let the lights get bright 
> enough when it is installed because we don't know what the resistance 
> readings are supposed to be.  If it shows 0-80 ohms we'll know if it 
> works but what if the switch is supposed to be 0-100 ohms?  Do you know 
> what the resistance readings are?"
> 
> Can anyone answer this?
> 
> Many thanks
> 
> Robert
> 63 Polara 500
> England
> 
> 
> Bill Watson wrote:
> > 
> > 
> > If you have a push-pull type headlmap switch, the instrunent panel 
> > dimmer is
> > in the switch.  If you have toggle or rocker switches, there is a 
> > separate
> > control for the dimmer.
> > 
> > The 1969-70 Polara and Monaco models had a rocker switch for the 
> > headlamps
> > with a wheel next to it for the instrument panel brightness and interior
> > dome lamp.   1964-66 Studebakers had a rocker switch for the headlamps 
> > and
> > one for the instrument panel lights.  The panel rocker, which got its 
> > power
> > through the headlamp switch, had off, low and high, and there was a 
> > small
> > rheostat under the dash that was used to fine tune the brightness.
> > 
> > Bll
> > Vancouver, BC

Well as you know ohms is a measure of resistance.  So if you have a 
switch that reads "0" that means no resistance to the flow of 
electricity which should give you the brightest lights possible, 
assuming there are no other points of resistance in the circuit.  On the 
high end the number will move towards infinity meaning no current gets 
through.  
You could attach one lead from your ohm meter to the (+) terminal of a 
dash light and the other end to ground, rotate the dimmer switch, and 
watch the reading on the gauge rise or fall.  If you can't achieve a 
number close to "0" you have to start working backwards to find the 
point of high resistance.  It will most likely be the switch.  
These work by passing the current through a wire that has a known amount 
of resistance per inch.  It is the coiled wire you see on the switch.  
It's the same principal and type of wire used in a bread toaster.  As 
you rotate it there is a contact that touches the coil so that the 
current is either going through only a bit of the coiled wire or the 
full length.  These coils tend to get a build up of crud on them after a 
time due to the heat generated.  That's why, as has been suggested here, 
that sometimes rotating them back and forth will make them work better 
because you are knocking off the crud.

Paul L.
'63 Sport Fury
440/727
http://www.1962to1965mopar.ornocar.org/ml-lennemann63.html


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