LEDs are current driven, not voltage driven
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(well not strictly true
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- they do need a certain amount of volts in order to light up, but as you're reading 12V in the dash, that explanation will suffice).
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While you're showing 12V, it's possible that there's not enough current getting through.
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If something has shorted out causing the wiring in the loom to partially burnout, it may still allow the voltage through but not the amount of required current
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- i.e.
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the wire is acting as a resistor.
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Do you have any idea what current is required by each of these LED bulbs? A check of the supplier's website might yield the answer.
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If the bulbs are for example rated for 1 watt, they will require around 84 milliamps
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(12V divided by 1 watt
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= 0.083 x 1000).
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If your power supply cannot deliver this then they are not going to reach their full brightness.
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The way to test this would be to use a multimeter in amps mode
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(by switching the positive lead into the correct socked
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- ensure you put it back to volts etc.
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afterwards) and testing it in series with the bulb whilst it is power up
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- do not put the test leads across the bulb's terminals, it will short out the connection.
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I would do this by finding a way to affic some test wires to the terminals on the bulb bracket
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- maybe by using an empty old socket to carefully wedge some wires in place.
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I can then use the test wires to hook up the LED out of its socket to test that the connection is good.
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Once you're happy with that, remove one of the wires from the LED and hook it back up via the multimeter i.e.
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Here's a
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(terrible) diagram to make it easier to explain
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![Image](http://www.endangermice.co.uk/mr2/img_2008.jpg)
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Once you have it all hooked up, set your multimeter to read milliamps and see what the current draw is.
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Note down this result, it should be similar to the specifications but manufacturers have been known to lie a bit about the power output so it could be lower.
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One way to be sure is to get a 12v DC power supply and hook one of the LEDs straight up to that with the multimeter also in series.
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See how much current it is trying to draw which will give you an idea of the real rating
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- ensure the LED is lighting to the correct brightness.
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Hope this helps.
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It is definitely possible to replace the dash bulbs with LEDs I've been running them for the last five years in my MR2 without issue.
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They're the surface mount types and there are around 10 LEDs on each
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"bulb".
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If you can't make the required current, then I would suspect something is up in the loom or you have a bad connection somewhere.
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You really need to get this checked out.
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At best
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- the already burnt out wires will just burn out quickly and stop working.
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At worst, the increased resistance will cause them to heat up, potentially causing a fire.
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