Dash Light LED Conversion Write-Up

[ktm]

LED Dash Light Conversion

 

As posted, here is a short write-up regarding converting the dash lights in an S30 to LEDs. It is relatively straight-forward and easy, though I will say that it is time consuming if you want to do a nice job.

 

DISCLAIMER (borrowed from Afshin): First, electrical shorts can burn out your EFI and/or cause a car fire. I have no interest in anyone doing this and don’t know if it will work for you or not. I have no formal training and am only sharing what I did for myself. There is no guarantee nor should any inference whatsoever be made that anything posted below is correct or safe.

 

Cliff Notes: If you done blown up yourself, look in the mirror for liability.

 

Stock Lighting System

 

First, a little information regarding the dash light system. The dash lights in a 240z (you will need to verify the lighting circuit for other models) get their power from the green with white wire coming out from the combo switch. This wire controls the side marker lights and parking lights. The lights are on a circuit that is fed power via a red with blue (R/L) stripe wire. The R/L wire connects to the G/W wire somewhere behind the dash by the speedometer or tachometer. I could not see the connection as the harness is still wrapped in tape. The R/L wire then connects to the dimmer switch (potentiometer) with a female spade connector (that is, the connector on the end of the wire is a female spade). Power is then distributed to the lights from the dimmer switch (the dimmer switch here is connected to the R/L with a male spade).

 

The 240z dash lights only have one (1) R/L wire connecting to each light. The ground for the dash light is in the light receptacle itself. It is a small metal plate that makes contact with the gauge housing.

 

The gauge faces are illuminated with indirect lighting. The light from the stock bulb is reflected back onto the face of the gauge from the black bezel in the gauge face.

 

Understanding LEDs

 

LEDs or light emitting diodes are peculiar little critters. They range in intensity and size, though size is not related to intensity. LEDs, while bright, have viewing angle limitations. You must find the correct viewing angle for your application. The viewing angle is a cone of light the emanates from the top of the LED. Some LEDs have a very narrow viewing angle but are incredibly bright. Turn signal lights, for instance, would be a good application for such an LED.

 

For illuminating gauges, however, you will want an LED that has a broad viewing angle as this gives you some flexibility in their positioning within the housing.

 

LED’s illumination characteristics are described by millicandela or mcd. The higher the MCD rating, the brighter the LED. I used 5000 mcd LEDs in my conversion. I would suggest that 4000 mcd is the lowest you would want, as any lower and the gauges would be too dim. You can not simply increase the voltage to an LED to increase its output; you’ll melt the LED (ask me how I know – accident).

 

Saying that, LEDs are incredibly sensitive to voltage. Too much and you’ll fry the sucker, too little and it will not turn on. However, they draw VERY little amperage (20 mA is typical) and almost no heat is generated by an LED.

 

LEDs ARE polarized however. The longer ‘leg’ of the LED is the cathode and the shorter ‘leg’ is the anode. When wiring up an LED circuit in series, the first LED or lead LED cathode is attached to the power wire. The lead LED anode then connects to the second LED cathode and so on, until the last LED anode is connected to ground.

 

Determining You LED Circuit

 

First, you need to plan out your conversion. How many LEDs per gauge are you going to install, the size of the LEDs, how are you going to install the LEDs, how are you going to wire the LEDs, how are you going to route power and ground the LEDs, etc. I opted for 6 LEDs in both the speedometer and tachometer, and 4 LEDs in each of the gauge pods.

 

Once I determined my LED arrangement and planned out my circuit, I started shopping for LEDs. I bought my LEDs from www.theledlight.com. They have a much larger selection than www.Superbrightleds.com and had the LEDs with the viewing angle and luminosity that I was after. My LEDs are 5 mm, 5000 mcd with a 40 to 50 degree viewing angle (http://www.theledlight.com/5mmcoloredleds.html - the second item). They have a peak forward voltage (VF) of 3.5 volts and a minimum VF of 2.9 volts. Their amperage requirement is 20 mA. Note that the LED will have a brightness of 5000 mcd at 3.5 volts. At 2.9 volts, the brightness will not be 5000 mcd.

 

So now you have your circuit planned out and decided on the LED, the next step is determining how are you going to wire up your LEDs and how to supply the correct voltage. This is the easiest part of the whole conversion.

 

The charging system of a 240z theoretically provides approximately 14 volts. Using my LEDs above, I can wire 4 LEDs in series and ‘consume’ 4 x 3.5 volts = 14 volts. Thus, I do not need to drop my voltage to run 4 LEDs in series. If the voltage is less than 14 volts, my lights will not be as bright. However, if the voltage is MORE than 14 volts, I may be in trouble.

 

My tachometer and speedometer posed a problem though. I am using 6 LEDs and I would need 6 x 3.5 volts = 21 volts to run all 6 LEDs in series. I could run two sets of three LEDs, but this results in 3 x 3.5 volts = 10.5 volts. Thus, wiring up 3 LEDs in series to a 14 volt system would most likely fry the LEDs. I need a way to drop the voltage to 10.5 volts. This is where you use Ohm’s Law to determine the size of the resistor you will need to install to drop the voltage.

 

Ohm’s Law states that the resistance, R, is equal to the voltage drop (dV) divided by the amperage (A). For my case using 3 LEDs, my voltage drop is 14 – 10.5 volts = 3.5 volts. I would need to wire a 3.5 volt/0.02 A = 175 ohm resistor to the cathode of the lead LED to drop the voltage to 10.5 volts. This is exactly what I did. I ran two sets of three LEDs for the speedometer and tachometer and wired a 175 ohm resistor to the lead LED of each set.

 

Resistors are not polarized so it does not matter which end you connect to the lead LED cathode.

Connect the lead LED cathode to the R/L wire for each gauge. This will supply power to the LED when you turn the marker/parking lights on. The anode can either be grounded to the gauge case, or you can run a dedicated wire to a known good ground. I suggest the later.

I would also advise to make the connection between the R/L wire and the LED cathode a plug type connection. Attach a small length of wire to the other end of the cathode, or resistor if you are running one, and put a bullet or insulated spade connector on the other end. This way you can easily remove the gauges from the dash.

 

Installing the LEDs into the Gauges

 

I am not going to get into the details of how to install the LEDs inside the gauges, where to ground, etc. Needless to say, installing the LEDs inside of the gauges was the most aggravating and frustrating experience of the entire conversion.

 

Since the gauges are illuminated by indirect light, you need to install the LEDs as close to the front bezels as possible so that the faces receive as much reflected light as possible. I suggest painting the back side of the bezels with a gloss white finish.

 

There is no mounting point on the side of the gauges, thus, you will need to come up with a way to mount the LEDs. One the tachometer and speedometer, I was able to use duct tape to secure the LEDs to the side of the housings. However, you do not have that luxury with the three smaller gauges. I ultimately wound up using a silicone adhesive, but holding them in place until the adhesive set was a challenge.

 

I have found that it is best to attach wires to each LED leg, feed the wires through the old light openings in the back, and then attach the wires outside of the housing. Trying to connect the LED legs together directly and then install them inside the housing is difficult. Also, you will want to cover the legs of the LED with heat shrink or tape so that they do not short inside of the housing.

 

I hope this helps those of you interested in doing this conversion. Please feel free to ask questions in this thread.

 

 

[ktm]

Added information on what wire(s) to tap into.....small oversight.

[gearheadstik]

Neato...Thanks for the info.

[Daeron]

this ain't my cup of rice-wine.. BUT, it is a well written write up.

 

Motion for sticky?

 

personally, I kinda like the feel of old school incandescent illumination. Then again, I prefer the older typeface on my gauges, too.. So basically I guess I am saying that I think KTM was 100% wrong in what he did

 

BUT, It was a good read, and it allowed me to finally decide AGAINST wanting to even think about this.

(oh, and KTM, I hope you pick up on the humor involved in me saying you were "wrong")

[Teekass]

personally, I kinda like the feel of old school incandescent illumination. Then again, I prefer the older typeface on my gauges, too.. So basically I guess I am saying that I think KTM was 100% wrong in what he did

 

BUT, It was a good read, and it allowed me to finally decide AGAINST wanting to even think about this.

 

(oh, and KTM, I hope you pick up on the humor involved in me saying you were "wrong")

 

Hey Daeron, I thought you were just saying that you're old ....LOL.

[Daeron]

Hey Daeron, I thought you were just saying that you're old ....LOL.

 

whiskey-tango-foxtrot!?! I never realized that the postbit here doesnt display my age, even though I try to always check the checkbox that shows my age...

 

Dude, I'm only 26... thing is, all of those years have been spent in S30 Z-cars. (okay, there were 2 280ZXs and a couple of Z31s too.. but they don't count ) SO, I am kinda sentimentally attached to certain bits of the car. The dim green lighting, surging with the RPMs is one of those things.. the older style typeface on the gauges (pre-77) is another.. I am not your top-not "HybridZ" material in every sense, heh...

 

On a side note, I rather prefer for everyone's age to post in their little header there on the side of our posts (thats what the "postbit" is) because it kind of gives something of a litmus test on their opinions.. Age doesn't ALWAYS equate to knowledge, but I am more willing to give weight to the opinions of a 40 year old than a 20 year old, everything else being equal.

 

I'm off to double check that I didnt leave a checkbox unchecked.

[Teekass]

whiskey-tango-foxtrot!?! I never realized that the postbit here doesnt display my age, even though I try to always check the checkbox that shows my age...

 

Dude, I'm only 26... thing is, all of those years have been spent in S30 Z-cars. (okay, there were 2 280ZXs and a couple of Z31s too.. but they don't count ) SO, I am kinda sentimentally attached to certain bits of the car. The dim green lighting, surging with the RPMs is one of those things.. the older style typeface on the gauges (pre-77) is another.. I am not your top-not "HybridZ" material in every sense, heh...

 

On a side note, I rather prefer for everyone's age to post in their little header there on the side of our posts (thats what the "postbit" is) because it kind of gives something of a litmus test on their opinions.. Age doesn't ALWAYS equate to knowledge, but I am more willing to give weight to the opinions of a 40 year old than a 20 year old, everything else being equal.

 

I'm off to double check that I didnt leave a checkbox unchecked.

 

I knew you'd get a kick out of my age crack:ass:....wait, not that kind of crack!

 

I really had no idea how old you were. I'm 37, but new to s30's. I've done a few sbc engine swaps in other body styles, but the Z is by far my favorite.

 

As far as the "HybridZ material in every sense," I'm a little strange myself.....I put a sbc in a '77, but in some aspects (interior, console, etc.) I like a clean factory look....wierd !

 

I'll sign off this way.....you know this one?

 

alpha-mike-foxtrot

[TrumpetRhapsody]

Digging up and old thread... I bought 7 BA9s-W's from SuperBrightLeds.com to see how they'd fair.

 

The specs say they have a 180* viewing angle and 11200mcd, and I intend to keep them behind the green tint cap thingies, so hopefully they'll work out alright.

 

I'm just looking for something brighter than stock, and the less amp draw will be nice, so nothing fancy.

[Careless]

i bought some 74w bulbs for various 87 Z31T dash guages and some larger 195 (i think) bulbs that I have yet to fit to the cluster.

 

They require some modification to the actual bulb to fit the original housings, which I reused. Nothing that a dremel and 30 minutes of griding with a fine tool can't fix. they look AWESOME, and have a better green colour overall than the original green-condom incandescent bulbs.

 

Also, they work with the factory PWM switch that is integrated into the dash via the push button to control the lighting of the digital display. Only when the lights are set to the full on position though! It looks amazing and is way easier to read. Now if Only I could pull out my cluster and get the plastic sheet removed so I can colour match it with some Parcan Gel sheets!

[rags]

Chris, how did the white LED's work behind the green lenses? I'm unsure if I should use the white or green since the lenses are green. Did the bulbes fit ok in the lenses?

 

Joe

[TrumpetRhapsody]

No, the blubs were barely too long. They wouldn't clip in. I had to remove the lenses for the bulbs to fit. They look awesome without the lenses though, beautiful white light, about the same visual light output as before.

[ugly]

So how much do LEDs dim? I am really sensitive to light when driving at night and like the ability to dim the dash to reduce irritation. Most modern cars won't dim because they are LCDs (white face gauges are the worst) and LEDs are the same. So I am wondering if you are losing your dimming capability when you do this?

I'm sure I am the antitheses here but an eight hour road trip on dark roads with a glaring dashboard is major eye strain. And fatigue behind the wheel is never a good thing.

[TrumpetRhapsody]

My LED dash does not dim.

 

For some reason I thought that leaving one incandescent bulb in would allow the LED's to dim... but I could be crazy.

[Daeron]

My LED dash does not dim.

 

For some reason I thought that leaving one incandescent bulb in would allow the LED's to dim... but I could be crazy.

 

Okayyyy, I am no LED professor here, but my understanding leads me to believe that you are crazy. IF a method for dimming the LED illumination were found, it would involve alot more complex circuitry than the simple rheostat potentiometer used to decrease the voltage to the circuit for the incandescent bulbs.

 

I would LOVE to know if a setup that allows dimming were available, and how much it would cost.. but I am fairly certain that it would take "a setup."

[sweetleaf]

They can be dimmed. It requires a PWM circuit. Not very complex.

[TrumpetRhapsody]

Well all I know is that I'm using LED bulbs from the same company in my Buick Regal, and they dim just fine. However that is because I didn't replace all of the bulbs with LEDS, hence my previous crazyiness.

[Hey_Allen]

Your Buick might have a PWM dimmer circuit, rather than a simple potentiometer.

 

By pulsing the power at varying rates, you can get the appearance of different light levels from a LED or incandescent bulb, and with less wasted power through heat in the resistor of a potentiometer based dimmer.

[Careless]

Allow me to profess.

 

He is not crazy. He is looking for what is called a Pulse Width Modulation circuit.

 

It uses a 555 Timer IC to control a pulse of 12 volts at a variably-adjustable (via potentiometer, a.k.a. dimmer dial) rate, and the bursts of 12volts will either have enough to keep it lit 100% percent of the time, 0% of the time, or anywhere in between, using the cool-down and start-up time of the LED to control the frequency of the light you see.

 

Some people with very sensitive eyes may notice flickering, and some people with prolonged exposure to the bulbs this way will not notice it but suffer from the fatigue, but it's rare.

 

 

Okayyyy, I am no LED professor here, but my understanding leads me to believe that you are crazy. IF a method for dimming the LED illumination were found, it would involve alot more complex circuitry than the simple rheostat potentiometer used to decrease the voltage to the circuit for the incandescent bulbs.

 

I would LOVE to know if a setup that allows dimming were available, and how much it would cost.. but I am fairly certain that it would take "a setup."

[Daeron]

Allow me to profess.

 

Foot firmly inserted into mouth; many thanks

[Careless]

LOL. the circuitry is not complex by many of today's standards and what others are doing on this forum, but it does take some soldering and general IC circuit knowledge (i.e. - which side of the chip is up?!) LOL

 

555 timer IC's are squarish in size, so that's the biggest problem with them.