Is it ok to fit an led bulb into the brake warning dash light (U.S. models). I've had two of the built in diodes fail in a short space of time, i'm now stuffed, mine is the 3 pole type, you press in the spring loaded red 'B' button to test the bulb. the one that just failed did so straight after fitting an led bulb !, coincidence maybe?.
Yes, the switch may fail if insufficient current flows through it to cause an arc that "cleans" the contacts of oxide. It may recover if you connect a filament bulb.. An LED may not drain enough current .. The 1.2W filament bulb draws 1 amp dropping to 0.1 amp once it glows white hot. An LED may be drawing about 0.02 amps.
I have re-fitted a normal 1.2w but no joy, are you saying that fitting an led bulb can kill the diode?.
Yes, low current drain stops the contacts of switches and relays from cleaning. So they fail. When you buy a switch, or relay from a quality parts supplier rather than the bazaars of China, one of the specification points is the minimum as well as maximum current. You may have to operate the switch a lot. Or it could just be early-life failure where it may even have worked when tested but then it breaks - the well-known "bathtub" curve where the failure rate of very new stuff is very high, but once it has survived a few weeks most items will remain working until the product begins to die of old age. .
Enlightening info Mike, ive operated it numerous times with a standard bulb in, it will work every time pushing the red button in which is the bulb test circuit, this has its own + feed. When putting a + feed to the other terminal which goes through the diode to simulate a brake fluid pressure drop , no light!, so i presume the diode has failed. This all a bit beyond my electrickey limits, i can't solder for toffee let alone minute diode surgery. I'll try and add a pic, not at home at the mo.
Are you sure you’ve got that kind of pushbutton? Some have a transistor in as well. With the one in your picture, no reason why it should go pop (what went pop BTW?), even if the LED is in the wrong way round.
Hiya, just a diode in there,. i think the original diode just died of natural causes, a friend fitted a good diode out of a spare switch and it worked ok,. put an led in, diode failed again, maybe coincidence, works ok on bulb test , ie pushing button in with any bulb in.
Only thing that would cause the (non-LED) diode to go pop is if the bulb contacts are somehow shorted together. A while ago, I tried to fix a fancier one and gave up in the end as the ancient contacts kept moving around.
I’d take a squint at the contacts first. All leads off, get your meter on low ohms and measure the resistance between K and the ground terminal. Try it both ways round. If you get a genuine 0 ohms, something’s shorted inside.
I have met really nasty LED bulbs where fiddling with them makes the LED move and causes wires inside to cross and short the two base terminals together. The wires inside then fuse. Something like that could pop an external diode.
The more i think about it i reckon the red led i 'tried' with both diodes probably caused their demise, it seems to much for coincidence. The led is probably reasonable quality though as it came from ClassicCarLEDs. Thing is..... what now
Are you handy with a soldering iron? The internal diode (if it has failed) will just be a boggo thing like a 1N4148. If you need some, PM me and I'll stick some in the post. Or if you want, send me the switch and I'll have a fiddle with it. Your brakes will still work in the meantime
Actually you wouldn't believe how inexperienced i am at soldering. I'd be happy to send it to you, very kind of you to offer Old Bean, better than lobbing it over the fence. It's a 'blocking' diode i read?. These switches are like rocking horse *h** to get hold off.
