Tach Needle going out
03-10-12, 10:59 PM
#1
Driver School Candidate
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Tach Needle going out
There's a section of my tach needle that either goes dim or goes completely out. It's strange because it only seems to go out during the day but come back on at night. I hear that this is a common issue so I was wondering what action I should take?
03-10-12, 11:02 PM
#2
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your not alone one this one, i have the same problem with my gas gauge and some other needles too. id be interested to know what people suggest, and if there are any alternatives to a dash swap
03-11-12, 04:17 PM
#8
You ask why your needles don't give you as much trouble with the headlights on. Try this experiment here:
go outside and turn your dimmer switch just off of the high position click (full on) down with your headlights off. Didnt make a hill of beans difference did it? NOW keep it in that position and turn the headlights on.
They dimmed! That's because the headlight circut will activate the second stage in the dimmer module when on and cut exactly .5 volt from the cluster. This is JUST ENOUGH to give the led's a slight break from "full voltage". That dimmer module is not just a ****, inside are a few chips and some diodes that regulate two lines to the cluster. one of them is full on (no headlights) one is controlled on (headlights on) which no matter what you do will always keep the cluster at .5 volt lower than the other way.
Why? Lexus didn't actually plan on this to happen (actually nippendenso since they make the unit). It is simple electronic theory, more easily said "it's the way it is" . See, whan you add a diode inline it drops the voltage of the line exactly .5 to .6 volt. This is one of the characteristics of the diode in an electronic circut. It just happens that you can see this little quirk of electronic technology since the needles that are sufficiently damaged are leaning on the brink of self destruction if that little tiny amount of energy is applied and helps finish overheating them.
go outside and turn your dimmer switch just off of the high position click (full on) down with your headlights off. Didnt make a hill of beans difference did it? NOW keep it in that position and turn the headlights on.
They dimmed! That's because the headlight circut will activate the second stage in the dimmer module when on and cut exactly .5 volt from the cluster. This is JUST ENOUGH to give the led's a slight break from "full voltage". That dimmer module is not just a ****, inside are a few chips and some diodes that regulate two lines to the cluster. one of them is full on (no headlights) one is controlled on (headlights on) which no matter what you do will always keep the cluster at .5 volt lower than the other way.
Why? Lexus didn't actually plan on this to happen (actually nippendenso since they make the unit). It is simple electronic theory, more easily said "it's the way it is" . See, whan you add a diode inline it drops the voltage of the line exactly .5 to .6 volt. This is one of the characteristics of the diode in an electronic circut. It just happens that you can see this little quirk of electronic technology since the needles that are sufficiently damaged are leaning on the brink of self destruction if that little tiny amount of energy is applied and helps finish overheating them.
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