Dash light dimmer switch

Gotta love that wiring . . .
zachmac
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Your car is a: 1978 Spider [1979 2 ltr engine]
Location: Aiken, SC

Dash light dimmer switch

Postby zachmac » Sun Oct 05, 2014 8:47 am

The PO had eliminated the instrument light dimmer so they were just always on whenever parking lights or headlights were on. I may leave it that way although there are occasions where dimming or off is a nice option, particularly as I plan to go either 5 watt or LED bulbs.

I sourced a used rheostat BUT it seems to actually only be functioning as on or off. I opened it up and found out how it works; clever little design with the ball bearings sweeping the hard contacts across progressively more of the otherwise higher resistance fine wire path. As it goes from off (full counterclockwise) to on (full clockwise) I assume I have an open somewhere in the resistance part of the switch. Previous posts have mentioned an internal fuse / fine wire? Would that be the wire between the two fine wire windings? It was hard to see if it is connected but i guess I can reopen the switch and check for continuity?

Looking for advise, but maybe I'll just replace it with a simple push/pull, on/off switch? Has anyone found a good generic replacement dash light dimmer switch perhaps from another vehicle that works / blends? A smaller one would be good as the center dash section has also had an oil pressure and ammeter added to space is at a premium.
Jeff Klein, Aiken, SC
1980 FI Spider, Veridian with Tan (sold about a year ago), in the market for another project
1989 Spider, sold
2008 Mercedes SL65
2008 S600 Mercedes V12

TX82FIAT
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Your car is a: 82 Fiat Spider 2000 CSO
Location: San Antonio

Re: Dash light dimmer switch

Postby TX82FIAT » Sun Oct 05, 2014 10:00 am

I bypassed the dimmer/reostat with a jumper wire behind the dash. Use LED's in dash as well. If it is light outside you can not even tell the lights are on.
Buon giro a tutti! - enjoy the ride!

82 Fiat Spider 2000
03 BMW M3
07 Chevy Suburban

spider2081
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Re: Dash light dimmer switch

Postby spider2081 » Sun Oct 05, 2014 9:18 pm

With out opening the dimmer you can check it's resistance. Full bright zero ohms. Rotating toward off the resistance increases to about 4.5 ohms when it clicks its off and resistance is infinite. If the little fuse link is blown the resistance between the rheostat terminals will be infinite all the time. I solder in one strand of the wire strands from a # 16 stranded wire to repair the dimmers.
If you install some LED bulbs their current draw could be so low the on/off function of the dimmer will work but the dimmer will appear to not be working. Other LED replacements do dim.

msrichmond
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Your car is a: 1977 Fiat 124 Spider

Re: Dash light dimmer switch

Postby msrichmond » Tue Oct 14, 2014 1:48 am

How did you open it? I don't see how to get the knob off without destroying it. I do see how the rear tabs allow the assembly to come apart once the knob is off.

MikeR

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Re: Dash light dimmer switch

Postby spider2081 » Tue Oct 14, 2014 7:47 am

On mine I just bent back the 3 little tabs holding the back on. No need to remove the knob, the shaft and knob stay in place with the metal housing.

Keep the knob facing down as there are small metal balls used as the contact wipers that will fall out if you tip it over.

msrichmond
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Re: Dash light dimmer switch

Postby msrichmond » Tue Oct 14, 2014 11:10 am

D'oh! Thanks!

MikeR

PhillySpider
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Re: Dash light dimmer switch

Postby PhillySpider » Thu Apr 27, 2017 10:58 am

spider2081 wrote:With out opening the dimmer you can check it's resistance. Full bright zero ohms. Rotating toward off the resistance increases to about 4.5 ohms when it clicks its off and resistance is infinite. If the little fuse link is blown the resistance between the rheostat terminals will be infinite all the time. I solder in one strand of the wire strands from a # 16 stranded wire to repair the dimmers.
If you install some LED bulbs their current draw could be so low the on/off function of the dimmer will work but the dimmer will appear to not be working. Other LED replacements do dim.


Old thread, but does anyone have detail on where this "little fuse link" is? A pic would be fan flippin tastic!

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Spiderman80
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Your car is a: 1980 Pininfarina Fiat Spider 2000

Re: Dash light dimmer switch

Postby Spiderman80 » Thu Aug 29, 2019 11:38 pm

Looking for a picture of the dimmer internal "fuse" as well...

spider2081
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Re: Dash light dimmer switch

Postby spider2081 » Fri Aug 30, 2019 7:45 am

I don't have a photo but looking at the back connectors of the dimmer there are 2 short brass terminals in addition to the 2 terminals the cars wires connect to. Internally (on the other end) the fuse is spot welded to these terminals. If connecting an ohm meter to the rheostats wire terminals the unit checks open ( infinite) resistance the fuse is most likely blown. The dimmer can be made workable by soldering a 5 amp fuse between the short terminals not used by the cars wire connections. Hope this helps

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Spiderman80
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Re: Dash light dimmer switch

Postby Spiderman80 » Fri Aug 30, 2019 9:09 pm

It does. Thanks!

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geospider
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Re: Dash light dimmer switch

Postby geospider » Sat Aug 31, 2019 10:38 am

Ok, dumb question # ?? (there have been so many) . All this talk of a dimmer; where is it?
the only knob that spins is the trip odom.
I'd like to know how bright, or not, the gauge panel lights get before putting brighter bulbs in.

Geo

tima01864
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Re: Dash light dimmer switch

Postby tima01864 » Sat Aug 31, 2019 3:10 pm

May be a dumb answer but as I remember on the pre 83 Spiders it is on the upper console on a knob with a light bulb icon

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Spiderman80
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Re: Dash light dimmer switch

Postby Spiderman80 » Sat Aug 31, 2019 6:18 pm

It's knob on right of center console. It's held in place by chrome collar. Be careful taking it out as it requires a little finessing.

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geospider
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Re: Dash light dimmer switch

Postby geospider » Mon Sep 02, 2019 11:20 am

yep, I'm an idiot; found it. Have even turned it before. But suddenly with this post forgot it all

JohnMc
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Re: Dash light dimmer switch

Postby JohnMc » Wed Sep 04, 2019 1:03 am

The dimmer INHO is kind of useless. I can understand why others have bypassed it to actually get a little more light on the gauges. Currently mine are dim or more dim. Just too lazy to go in and bypass.


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