single
Well-Known Member
I bought some LED bulbs to replace the standard filament type 12v 2w for the instrument lights. When i turn the ignition on they just flash on/off very quickly but won't stay on.Why is that?
LED bulbs
- Thread starter single
- Start date
Tim Good
Well-Known Member
Unsure but might be the lack of resistance or lack of current draw. I replaced my masthead tricolour and the indicator lights to say which of my lights are on now just flashes on and then off and stays off. I'm assuming that indicator light was activated by some current draw which is now so small it doesn't register. Might be something similar in your case.
VicS
Well-Known Member
What have you bought exactly ?
and when you say "instrument lights" you mean instrument illumination ?
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JumbleDuck
Well-Known Member
Old fashioned car voltage regulators work by switching on and off as required to maintain the right average voltage. Have you an ancient engine with something of that sort lurking?
VicS
Well-Known Member
You are thinking of the old electro-mechanical regulators that powered the fuel, temp and perhaps oil pressure gauges. AFAIK the illumination was off the full voltage.
single
Well-Known Member
I bought these http://www.ebay.co.uk/itm/351222056529?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
To replace these for the back of the oil temp,water,rev etc
View attachment 49994
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VicS
Well-Known Member
I'd expect them to be Ok. Perhaps as JD suggests there is some kind of voltage regulator or brightness reducing or control device. Have you tried them directly on a 12 v supply ?
Anything indicated on the engine wiring diagram that might be the cause ofthe trouble?
single
Well-Known Member
They work fine from my bench supply. I'll check the wiring diagram later. (Thornycroft T95 delux instrument panel)
JumbleDuck
Well-Known Member
That's the one, and yes, normally only used for hot-wire gauges which don't mind a PWM input. Someone might have used one of them creatively!
