Which switch do I need

[dlotz]

Hey guys

Which one of these switches do I need for the Dash dimmer knob?

http://www.holden.co.uk/displayprodu...otary+Switches

I have the knob but need the correct switch to control the gauge lights (I have Smiths gauges). Is there a cheaper alternative I can pick up at a local autoparts store?

I would like to be able to also hook up my aftermarket interior courtsey lights to the same switch like in our modern cars where once you reach full brightness on the dimmer switch you can go one click past and it turns on the courtsey lights.

[strictlypersonl]

Rotary switch

[dlotz]

Anyone know of a cheaper, local (US) alternative??

[LMH]

You could try a rheostat from Radio Shack or similar place and see if you can put the correct knob on it. You'll need the correct ohm range which I'd say is 0-12.5 based on the ad from Holden.
Would be a lot cheaper for sure.
Larry

[trularin]

You could get a PWM module.

[FWB]

cole-herse makes most oem switches, they have a nice selection of retro- knobs also

[Gunner]

Originally Posted by LMH

You could try a rheostat from Radio Shack or similar place and see if you can put the correct knob on it. You'll need the correct ohm range which I'd say is 0-12.5 based on the ad from Holden.
Would be a lot cheaper for sure.
Larry

Rheostat is an old and automotive term. The term under which you'd find these things in a modern electronics supply house is "potentiometer."

You can't use an off-the-shelf pot for this job, as most are rated at only a few watts of power and will burn up at lower settings with an amp or two of lamp bulbs downstream. The ones used in cars are "wire-wound" pots (or rheostats) - it's the slider moving over those wire windings that gives the knob that "gritty" feel. Wirewound pots can handle 10, 20, even 100 watts depending on size and rating.

I think you'd have trouble finding a suitable one for automotive use, though. Adapting one from an automotive supplier or a junkyard (pardon me, "donor") part is probably a better idea. You could also use a switch and a couple of fixed resistors in the 5-watt range to have a bright-dim-dimmer-off selection.

[LMH]

Kind of, yes. A potentiometer (pot) is a three post variable resistor and a rheostat is a two post variable resistor. A pot can be wired as a rheostat by using only two of the posts.
The idea here is to use an original style knob but be able to still dim the dash lights w/o having to go into to debt with a second on your house. I'm sure some kind of pot or rheostat can be found online with the correct ohm range and glue the original knob on if need be. No one would know it wasn't a Lucas dimmer unless you knew to look for the correct trim ring under the knob.
Larry

[Gunner]

Everyone will know it's not a Lucas because it works.

Except in perhaps theatrical lighting circles, rheostat is a very antiquated term. The two-terminal/three-terminal thing isn't a distinguishing feature; many heavy duty lighting rheostats have three terminals for balance wiring.

Terminology aside, it sounds like a good place for a wrecking yard hunt for a switch of the right size and function. They are kind of bulky, but the ones from early Mustangs might make an adaptable item.

[computerworks]

Originally Posted by Gunner

Rheostat is an old and automotive term. The term under which you'd find these things in a modern electronics supply house is "potentiometer."

A rheostat is a two-terminal variable resistor; a potentiometer is a three-terminal variable.

You could wire a pot to act as a rheostat, electrically.

Most pots are very low wattage; the rheostat term is used here because most rheostats in this application are wirewound and can handle the higher lamp currents directly.

[Gunner]

Tomato, tomahto.

I spent 15 years in electronics design and a few years here and there in things like theatrical lighting, independent power generation and the like. The terms are completely interchangeable except that no one in electronics (since about 1945) calls them rheostats. Since he was being directed to Radio Shack to find a part, pointing out that the ignorant nebbish behind the counter isn't going have a freaking clue what a "rheostat" is was intended to be helpful.

Nor is the guy at the wrecking yard likely to know what a pot is. Theatrical crew, flip a coin; the older ones and ones who work on really large gear call them rheostats, the newer guys and ones who work with small theater gear call them pots.

[computerworks]

Fabulous.
It's a rheostat.

:-)

[LMH]

Isn't an early Mustang dimmer part of a pull-type light switch?
If it is, it isn't applicable IMO as the shaft is way too small for the Lucas knob and the pull switch isn't needed.
Larry

[mickmate]

I found a couple of good used ones off e-bay, you're still stuck $$ finding correct knob and ring.

[LMH]

Anybody know off hand what the wattage of one dash light is? Like from a Smiths guage.
How many total lights in one of our typical dashes?
Larry

[mickmate]

Hey Larry I don't know off hand but it's all listed in the owners manual with a lot of other good juju.

[PANAVIA]

you could use a regular headlight switch and only use it for the dimmer portion.

[LMH]

Originally Posted by mickmate

Hey Larry I don't know off hand but it's all listed in the owners manual with a lot of other good juju.

Good idea. I'll check.
Larry

[aks801]

I use the term rheostat, thought everyone did. Does this make me antiquated? I'm only 48....

[Ronbo]

Reostat is typically the term for high power - wire wound variable resistors. Potentiometers is generally associated with the carbon / ceramic variable resistors. I've seen the term flopped around over the years.

They're all variable resistors...

IEEE would be the group that determines the definition if you really care (I don't).