67 headlight switch w /U17 console instruments

[My68SS]

It may be that the max resistance of the dimmer fitted is different depending on options and therefore the number of lamps [total current] it has to control, so the same dimming range is acheived.
Might be interesting for those with dimmers lying around and a good, accurate low ohms reading dmm to measure their dimmers along with what number it has stamped on it.

[flyingskibiker]

My ~11C '68 has 164 on the side.  Here to help... ;-)

[big iron]

Rob,
 I believe there is a physical difference in the size of the ceramic material that the dimmer w/gauges has that also allows for a higher wattage capacity in the dim position.
I have seen replacements that the dimmer section is 2x the size of the 147 that I have.
The 67 console w/gauges and 4 spd. have 5 additional lights and w/auto trans. 7. For the dimmer to dim the additional lights you would have to increase the dimmer resistance to drop more of the voltage at the dimmer.
There are 4 dash,2 court. and 1 dome ( 2 deluxe) = 8 lamps so you would need probably 2X the resistance of the 147 sw.
My original 147 shows 0 to 7 ohms across the resistor, measured with a Fluke 83. I used the # 3 trem. and the wiper for my measurement. I also tried term #2 and term#3 and could only get 0 to 6.3 ohms.
Bob

[big iron]

Does your build have a console w/ gauges?
Is it stamped on the plastic or the metal bottom?
Bob

My ~11C '68 has 164 on the side.  Here to help... ;-)

[flyingskibiker]

No idea if car came w/ gauges from the factory...  The car does have the tic-toc-tach and most wires match up w/ that (clock power w/ correct connector).  But the harness is pretty well hacked and unwrapped.  I haven't checked to see if the wires going to the aftermarket gauges are the correct color and go into the bundle of wires under there (gauges are mounted under the center of the dash where the U17s would be).  I will be doing that in the next couple months since I plan on replacing the harness and installing a console w/ gauges.  There IS the correct oil line hole in the firewall.  I did check that.  There is also a hole for the Muncie speed-o cable and jumper harness and hole for the back up lights.

If I look in the instrument cluster opening w/ them out of the car like they are now, I can look at the side of the switch and see it stamped into the metal near the rear of the switch.  It is not on the bottom as the switch is currently mounted.  The switch know release button is on the same side facing the cluster opening, as well.  I could take a picture pretty easily...

I bought an aftermarket switch.  I could easily measure the resistance on it.

[My68SS]

For the dimmer to dim the additional lights you would have to increase the dimmer resistance to drop more of the voltage at the dimmer.
Bob

Hi Bob,
It will be the other way round - more lamps = lower dimmer resistance.
e.g. For a given dimmer position/resistance, as you clip more lamps in parallel, the brightness of any one lamp decreases, as more voltage is dropped across the dimmer.

[Mark]

The resistance of the dimmer is fixed, its the wattage of the resistor that increases.  As you add more bulbs in parallel the circuit resistance gets lower, but the resistance thru any one bulb remains the same.

[My68SS]

The resistance of the dimmer is fixed, its the wattage of the resistor that increases.  As you add more bulbs in parallel the circuit resistance gets lower, but the resistance thru any one bulb remains the same.

That's true, more watts will be dissipated in the dimmer as you add more lamps. I was only wondering if they also changed the resistance of the dimmer to keep the same dimming range.
It may well be that this was considered of minor consequence and only the wattage of the dimmer was considered.

Having said that though, to some extent the two would go hand in hand anyway, higher wattage capability = heavier wire = lower resistance anyway [for roughly similar wire lengths]