I bought my SC about a year back and the guy I bought it from had lextech needles done, bright white. about 2 weeks ago, my speedo needle started to flicker while I was driving and then turn off then back on, then flicker again then off.

Its been doing the same thing for the last couple of weeks is this something with the needle or do you think its another problem. I have searched about the flicker of stock needles but im not sure why they do it.

Any input would be much appreciated.

 

shouldn't be flickering, even though I've heard of a few people getting flickering/burnt out needles after getting them redone. They usually flicker when the smd is starting to go out.

 

whats the SMD? Sorry not very electronically incline lol

 

Lexus needles are pita. I have lextech needles now but I prefer stock led ones. I have a good set of 95 needles but I noticed polarity is switched lol. I'm thinking of modding it to work.

 

I like the lextech ones, they look great but the flickering is killing me. Im not sure even where to start on getting this fix.

 

why not consult lextech?

 

Flickering could be from bad contacts, corrosion.

 

Well I'm not sure there is much they can do. It seems to be a problem in my car.

Now when it starts to flicker if I dim it down it stays on. But after awhile it starts to flicker again and turns off. If I put the dimmerall the way up it flickers again and turns off. Weird.

Where should I start with troubleshooting?

 

You could have just emailed LLS. They have a lifetime wty. The stock needles fail due to heat, aftermarket needles fail due to voltage spikes. If your car proves to have spikes, LLS just bumps them up with a buffer to handle any spikes. The flickering is from the gate in the led being damaged from the voltage rush. SC's notoriously have the worst spike of any cars on the planet, some just have them even more than others depending on mileage and such.

 

How good are you with tools and a meter? Look for the specs for the needles online...Meter them out yourself and see what the problem is.

I imagine it would be a pain in the butt to do it with the gauge pod removed and hanging out. And unless you have it set up where you can bench test electronic, I guess I would just send it in if you say No to any of those.

 

Here's the easy version.......

LED's have a gate that is very small and similar to the CMOS gate in a computer chip. They are sensitive and can't handle much of any voltage. Static discharge from your hands can even kill them, though it is less likely you'll hurt one with the average charge on your fingers.

You can't run an LED on all the time. When you look at the needles in the lexus cluster they have a PWM (pulse width modulated) voltage supply that is only on a percentage of the time. If you lower the frequency of the voltage (how long the pulse in on) you'd see the led flashing. It's called "on time". The average LED's on time is 70% preset by Lexus in their chips that drive the needles. This was too high of a setting, unfortunately the chip was predesigned internally and etched with fixed resistors inside the chip so you get what you get. 70% on all the time. This creates too much heat from being on too long before it cycles off for 30% and back on another 70%. The result is melted needles.

LLS designed your needles to take an on time of 63% with consideration for voltage spikes. A circuit similar to the one seen below is built and integrated into every cluster when the unit is built and hand tuned to hit a certain on time peak on the oscilloscope.

If your car has harsher spikes for any of the millions of reasons (old bulbs, bad grounds, old alternator, etc...) the only way to know it is gonna happen is to live it and see. If it does, the unit gets retuned to 55% on time and it eliminate the problem. Initially this conservative setting is not used because it is a compromise to how much on time, hence how bright it appears.

Voltage only kills led's when they are spiked or left on all the time. NO led is designed to be at 100% on time, that is not how silicone gates work. That's why the DIY's only end up dying off in a few months. If it is done backyard without proper technology designed into it, it'll fail. Every electronics student, tech, engineer, or specialist that has ever had any college in the field knows you can't leave an LED on 100% of the time without killing the gate. So you can't just "put a resistor on it and hope it works". Resistors only control voltage, you have to build a timer to control on time. You have to design a timer circuit and use it on every single led or beef it up to run a cluster of them. This is the difference in a professionally designed unit and a resistor stuck in the back of an LED in a DIY. There are consequences to half assing anything. You unit just needs to be rebuilt and tweaked to 55% on time to eliminate whatever variable in your car is causing the heavy spikes.

Now here's the real trick... when you build a more complicated working version of the basic unit below, you have to integrate it into the current frequency chip in the lexus unit and make it work together to 55%. That's why nobody ever explains anything and just says "send it back in for a rebuild". Let the diy guys stick to killing led's @ 100% power, these are designed systems you don't have to worry about. If there's an issue just send it back in and don't worry that's for them to worry with for you. They'll tweak it and set the tune to a new frequency and stop the issue.

Here's the equation for creating a pwm http://www.mathworks.com/access/help...agesource.html

I'm sure many math persons are familiar with RC Time Constant http://www.interfacebus.com/Design_R...ant_Graph.html

 

there is enough work involved removing the cluster. i purchased replacement needles off e-bay, they didn't work. not a simple plug-in replacement. read all the complications with lexus electrics, and ended up sending it in to LLC. am pleased with the results. it is pretty reasonable price considering the aggrivation no needles present.