Dash light dimmer switch

[zachmac]

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.

[TX82FIAT]

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.

[spider2081]

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]

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

[spider2081]

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]

D'oh! Thanks!

MikeR

[PhillySpider]

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!

[Spiderman80]

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

[spider2081]

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

[Spiderman80]

It does. Thanks!

[geospider]

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]

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

[Spiderman80]

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.

[geospider]

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

[JohnMc]

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.