Cheap LEDs for automotive dashboard application

If the light bulbs on the dashboard are burned out, that means that the car is way too old. Get a new car.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

Now there's a novel solution to replacing a light bolb that might not cross my mind too often. ;) I still have a 1979 VW rabbit working nicely, because I pull my own axles and replace bearings, etc.

Jon

Just give each LED its own series resistor, unless they come with them.

Then, other than the fact that you have to watch the polarity, they should be virtually drop-in replacements, as long as you can figure out some way to plug them into the dash.

Good Luck! RIch

Thanks...yes, I'm pretty sure I can get them placed/wired. I was more worried that they would have a reliability curve (in this application) that is worse than a standard incandescent bulb. My goal is to put something in place that will be very robust, since replacement is a very difficult task (on this car).

-Randy

"Randy MacKenna" wrote in message news: snipped-for-privacy@q4g2000prc.googlegroups.com...

Just get the $20 dollars or so of bulbs to replace everything when you have it apart. It'll last as long or even longer. There are long life bulbs that you can buy. Now the grain of wheat bulbs in radios thats a different story.

Cheers

I have never seen a car where the panel needed to be disassembled to replace the lamps. Sometimes its a bit of a chore getting your hand behind the panel, but the lamps are typically held in bases that can be removed with a quarter turn.

Many vehicles use a simple rheostat in series with the panel illumination circuit for dimming. With this arrangement, the LEDs will not dim properly. They will remain at near full brightness until some point is reached and then dim quite rapidly.

Some cars use a PWM dimmer. You could build one of these yourself and replace the dimmer rheostat, incorporating some protection against overvoltage.

Another thought just occurred to me - if the existing dimmer is just a rheostat in series with the +12 to the bulbs, then they might not dim the same as incandescents. But you'll have to poke around and find out about that.

Good Luck! Rich

My experience also. But you have to be a contortionist to get your hand in there. I typically lay upside down in the seat with my head under the dash :-(

Many times I've found that "dead" lamps had actually been shaken out of the dash. They usually are single wire with ground return via the PCB copper clad in the dash panel.

...Jim Thompson

Buy a new car? That just means that the job is too complicated for you, so you've thrown in the towel.

They laughed at me when I walked into the the parts department at the Ford dealership, disheveled, with blood dripping from my knuckles, carrying the radio, to get a new backlight bulb for it. I wrestled with that bastard of a job for a good long time before I got the radio out. Turns out that you can pop the thing out in a few seconds with a special tool, *AND* you can make the ^*%$*_ tool with a coat hangar. :-(

The parts guy was nice enough to give me the bulbs for free.

Ed

Skinned knuckles are de rigeur.

I recently bought a set of Japanese tools that allow removal of trim without bunging it up.

Also read the manual on my truck... to remove radio, remove glove box... ta-da ;-)

(I'm adding a new Panasonic "head" which has a Sirius port ;-)

...Jim Thompson

Same here. 1995 Golf. First dashboard light went out after 10 years, so I thought that when I changed all of them (not just the burnt-out one) I should be good for another 10 years.

So I spent $9 on new bulbs, half a year ago, but so far I've been to lazy to actually pull out the dashboard and do the work. Moreover, by now I can't remember where I put the new bulbs, so when the next light goes out and I'm forced to do the repair, I'll have to re-buy the bulbs.

What I'm trying to say is that the technology used for lighting (or not lighting) the dashboard is a secondary, if not tertiary concern. How old is your car?

robert

Thanks for all the replies. For the folks that can't believe the dash needs to be disassembled to change the instrument bulbs -- it's a 1997 Volvo 850. You absolutely have to remove the top of the dashboard, and pull the instrument cluster to get to the bulbs. I have a pretty well equipped garage, and do all my own repairs (including pulling engines if I need to), and this repair job has me twitching. The only reason I'm doing it is because I have to also replace the AC evaporator on this car...which means (you guessed it) the entire dashboard, steering wheel, airbags...everything...needs to come out.

Given the dimming complexities I think I'm going to abandon the LED idea. I just hope the replacement incandescents will last longer than the three years some of the originals did.

Randy

Ah yes, a Fluffo. You have my condolences ;-)

...Jim Thompson

I once had a '75 Plymouth Gran Fury. I believe it was a one-owner, who had died of old age. You could almost stand up on the floorboards under the dash -- well, I exaggerate, but it was really, really easy to work on. Even fun, actually. The dash lights had inside-out sockets - that is, from the back of the dash you can grab each socket/holder and "bayonet" it out, and the bulbs were those pop-out-pop-in kind.

When I had got it the tie rods were terribly worn so it kind of ate tires. It's an incredible feeling of accomplishment to swap out one's own tie rods, align the front end with a tape measure, and do tight turns around the parking lot without the front tires squealing. ;-)

Cheers! Rich

If you can, put a diode or 2 in series with them and they'll outlive the car.

Ed

In my Toyota FJ40, it is impossible to fit one's hand up behind the dashboard to access the lamp sockets. Fortunately, the entire instrument cluster is held in by two very prominent Phillips screws. Remove them (and a few plugs) and the entire panel may be brought to the workbench for maintenance.

Hmm. My (Japanese and German) vehicles have a bayonet type socket with two tabs that contact PCB traces on either side of the hole.

This would present somewhat of a problem for the OP, since one can reverse the polarity of the lamp. Not an issue for incandescents, but LEDs .....

The other problem I can see with LED replacements is that their optical output tends to be confined to a conical area directed forward. The existing lamps distribute light uniformly in a spherical space. If the instrument panel's light is taken from the sides of the lamps, LEDs won't direct much light where its needed.

Yeah, but who ever has any spare coathangers?

;-)