bulb / LED replacement for gauges

[qz16]

So, the white LEDs were to be delivered on 4/21, but they arrived yesterday 4/3.

For comparison (image 1) I installed 2 white LEDs in the Tach and I installed 1 white LED in the center gauge (AMP/Fuel).  The remainder of the gauges and the speedometer has Green LEDs.   Green LEDs populate all gauges in image 2. 

image: 1

 

 

image: 2

Edited April 4, 2020 by qz16

[w3wilkes]

I kind of like the effect of the white bulbs in the center gauge and tach. Are either dim-able? And lastly, why is your car upside down? ?

Edited April 4, 2020 by w3wilkes

[qz16]

The website for the LEDs that I bought says that they are dimmable.  I connected my dimmer and there was no discernible change.  So I measured the dimmer.  Mine measures out to be from 2 -11 ohms.

It occurred to me that this might be too little resistance for the LEDs.  I looked around but I did not have a spare dimmer of any sort.  I could not find any of the resistors that I have foolishly saved over the years on the off chance that I would have them when I needed them.

Its Sunday, I am trying to be a good citizen and not go out unless it is an absolute necessity.  When I was a kid I had some hobby kits where you build things and do experiments.  Anyway, here is the cool part (at least in my opinion), if you draw a box, on an ordinary piece of paper,  and fill it in with an ordinary pencil you will have created a resistor.  If you put an alligator clip with a wire attached to it on each side of the block you can measure the resistance that you just created.  If you want less resistance put the clips closer together, more resistance – space the clips further apart.

 

Homemade resistor

 

 

So W3wilkes – the answer to your question is that the recommended LEDs are dimmable.  I suspect that the dimmer in your Z (mine is a 1973 240z) may not work because the resistance in it is too low.  But if you get a dimmer in the 0 – 1k ohm range you will be able to dim these LEDs.

 

Here is a comparison:

LEDs with no dimmer (speedometer, oil/temp and clock) - Green LED

Tach and amp/fuel) White LED

 

LEDs with 458 ohms of dimmer resistance 

 

 

The next image has no dimming, Incandescent lamps in the speedometer, and clock, Green LED in Volt/Temp gauge, and white LEDs in the tach and amp/fuel gauge

 

You must take care in picking the resistance value if you mix incandescent lamps and LEDs.  You might be able to get away with using the original dimmer if you have a few incandcent bulbs and some LEDs.  I think I will try to go with one or the other.  My conclusion is that I prefer either the white LED with a dimmer or the incandescent lamps and a dimmer,  I might consider white LEDs in the speedometer and the Tach and incandescents in the 3 gauge set.

If you have a question dont hesitate.

[SteveJ]

Controlling the brightness works best by using a PWM. Read the attached for a quick overview.

ApplicationNote_SE-AP00040-E.pdf

[240znz]

I'm about to do the same and if at all possible, are you able to post link to the white LED's you purchased for all sizes and quantities required.

I have pulled the old dimmer of the 73 dash. It's buggered. What wattage 498ohm resistor did you use. Shouldn't be much heat generated dur tothelow wattage LED's there but better to be safe and not melt the dash.

Thanks

James

[qz16]

So, I purchased the LEDs via Amazon.  Below is the URL for the white LEDs.  I would suggest using White LEDs for the illumination of the gauges and the three lamps that light up the climate panel.  I believe the MAP and DOME lamps are different animal and I have not found the box with those fixtures so I cannot confirm that for you.

 

https://www.amazon.com/gp/product/B01C2SHQAY/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

 

So there are seven (7) lamps for the gauge illumination.

Three (3) lamps for what I believe is the climate panel.

One (1) for the glove box.

I do not have footwell lamps, but if you do that would be another Two (2) lamps.

The inspection lamp in the engine bay is another (1) lamp.

I don’t have seat belt warning, or choke warning lamps, but I believe these are lower wattage, and physically smaller bulbs.  Maybe similar to the indicator bulb for the rear defroster.  As you know this bulb is part of the switch.

This totals to fourteen (14) bulbs that I would White LEDs.

 

There are two (2) for the turn signals – I am using green LEDs – same URL -specify green.

There is one (1) for the high beam indicator – I am using Blue - same URL -specify green.

There is one (1) for the brake warning lamp – I am using Red - same URL -specify green.

 

If you use all white LEDs you will need 18.  If you use the same product that I ordered they come in packages of eight (8).  I would recommend that you order enough to have spares as mine took a few weeks to arrive.  Also, I can only list the bulb locations that I am aware of, so you may have a few more or less, depending upon your year and how original your car is after 40+ years.

With regard to the dimmer, I don't trust the anecdotal value that I came up with.  I believe Steve J is correct regarding PWM.  If you are still going to use an ordinary rheostat then I would probably find something in the 0-1000 ohm range

 

Hope this helps you.

 

Regards,

ron