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Instrument lights VERY dim, rheostat issue?


Naamis

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Hi all,

 

I've been thinking about replacing the bulbs as the instrument lights are VERY dim. In the dead of the night I can barely make out the gauges. Then I read in the forum post that there is a rheostat! I assumed this to be the  fix to all my woes, but it's already at full power. Going back and forth, it does dim the light even further. They are all as dim btw. I was wondering, is it possible the rheostat is just a bit "tired" and is there a good way of going about in diagnosing the actual issue as I would rather avoid pulling the dash or dislocating members from multiple locations.

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It does sound like the rheostat is either very dirty or just about had it.  You can remove the rheostat and just jumper the two wires together to test the circuit.

 

Hello Mr. ktm, would this scenario need dislocation of joints to get access to this trial? I've heard horror stories. 

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Apparently, light bulbs go dim over time, before the filament breaks and they quit working.  Plus, some of the instruments have more than one bulb.  If one goes, the gauge will be very dim.

 

Proper bulbs are hard to find but probably your best bet.  If you want to check the potentiometer you could just measure resistance through the circuit.  If you can get the connector off.

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I did not have any issues removing my rheostat as it is located on the bottom of the dash.  Granted, I was lying on my back with my head down by the gas pedal and using the steering wheel to pull myself up in order to see things, but where there is a will there is a way.

 

If it is just one gauge that is dim, then that would point to a bad bulb.  If all of your lights are dim, however, that is related to either the rheostat or the fuse panel.  Have you tried cleaning the contacts in the fuse block?

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The 280Z's  is buried up in there.  He didn't say what he's working on.

 

Should be easy to check at the plug though.  Can't remember if I ever checked mine or not.  I probably did and was disappointed that it wasn't bad.  So I had to replace a bunch of bulbs to get some brightness.

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I've done gauge work on both my 260Z and several other Z's.  If you took one apart you'd notice the following: 

The glass on the original bulb has become discolored.

The inside of the case used to be painted white - most of that is gone now.

The green plastic housing is covered with dust. (as is the rest of the gauge)

 

Now let's go back to the 70's...

These cars were produced in an era where "light pollution" was minimal.  Now there's a street light every few feet, shopping center on every corner, and 700% more headlights in your face...  Gauges weren't made to "stand out" like they do in modern cars.

 

LED "bulbs" make a large difference but I personally really dislike the harsh light they provide.  Using a 5W bulb to replace the 3.7W bulb makes a difference, but they're hard to find.  I like the green tint in my gauges, but I'm a child of the 60's - I grew up with green gauge lighting so I'll keep my green plastic housings thank you. 

 

What made the biggest difference in my gauges was renewing the white paint on the inside of the cases and cleaning everything up.  But that means removing the gauges and taking them apart.

 

I still use stock bulbs in mine and I have no problem reading any of my gauges, but again see above, I'm a child of the 60's, and don't want Z gauges as bright as the display panel of my G35.

 

I haven't yet run across a rheostat that was faulty or that couldn't be brought back with several full rotations of the knob.  Clean that spring wire off and it'll probably work just fine.

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