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photocrasher

Trouble with instrument lighting after LED swap

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Hey everyone - I recognize I'm much more of a lurker/reader than poster, but am hoping to get some input. Yesterday I undertook the task of swapping out my lights in the instrument panel. Great writeups here helped me get it out much easier than I expected. I ordered in from SuperbrightLEDs all of the bulbs that I would need, and switched everything over. However, now none of my instrument lights come on with the lights. My headlights and turn signals do work as expected, and if I turn on the high beams, the high beam indicator does function, but nothing else will (brake light, oil, alternator, signal indicator, or ambient lights). I'm guessing that the high beam indicator must be on a different circuit which is why that one is working.

 

I thought that the bulbs that I purchased were not picky about the polarity, but could be wrong. I've double checked to make sure all wires were reconnected properly, and double checked the ground. I suppose it's possible the polarity is it, so does anyone know which is the first bulb in the series to test if that's it? FWIW I'm not sure it's a polarity issue partly because the turn signal indicator and brake lamp or other warning lights are not dependent on the headlights to be on and they're not working either.

 

Any thoughts?

 

Thanks!

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1 hour ago, photocrasher said:

so does anyone know which is the first bulb in the series to test if that's it?

Bulbs are not in series like Christmas tree lights, but in parallel.  One not working will not affect any others on the same circuit.

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1 hour ago, photocrasher said:

I thought that the bulbs that I purchased were not picky about the polarity

LEDs are essentially diodes allowing current to flow only in one direction.  So, they are very picky about the polarity.

 

It does seem unlikely that all the LEDs were installed reversed.  First check your fuse box to make sure.  Then, try to install these LEDs one at a time testing polarity as you go.

 

Good luck.

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Maybe start with checking the connections at the back of the cluster. Also, I am not sure that replacing the alternator bulb with an LED is a good idea. It doesn’t work like normal bulbs, basically having current go in both directions depending upon which has the higher voltage (battery or alternator) and going out when the voltage on both sides is the same (zero potential difference). 

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Thanks everyone for the replies and suggestions. My game plan this evening is to swap around a couple of the bulbs to see if somehow my luck is outrageously bad and they are all somehow in reversed. If that yields no results will swap back in some of the original bulbs to test the panel itself. I’ll report back the results.

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Easiest to do this one on the bench.  Pull the cluster out, have all of your LEDs and one or two of the old filament bulbs on hand.  Take your power supply (extra 12V battery, old computer speakers power supply, or in a pinch just a plain old 9V battery will work) and hook it up (carefully, and with a fuse to be on the safe side) to the pins on the back of the cluster.  Positive goes to pin #4 and negative to pin #3:

image.png.95765b45b012ea930aa3d2deb04f5229.png

 

Then plug in an 'old' bulb into one of the sockets, make sure it works, and then take it out and replace it with the LED bulb, flipping it as necessary to get it to light up.

 

You can then continue with this method to cover all of the other indicator lights also, but since I already gave you the backlighting for free, I'll leave it up to you to sort out which pins on the cluster you need to power up to check the other indicator lights ;) (or you can PM me if you run into trouble with this).

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For the bulbs used to illuminate the instruments, make sure your LED replacements are dimmable-not all are.  The headlight switch rotates to dim the instruments, and LEDs that aren't meant do dim will function poorly, if at all on a dimmed circuit.  

 

And +1 on the alternator lamp--that lamp needs to be incandescent, as without it the alternator won't charge.  

 

mike

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(edited)
8 hours ago, Tsingtao_1903 said:

LEDs are essentially diodes allowing current to flow only in one direction.  So, they are very picky about the polarity.

Yes indeed.  I did the LED swap in my instrument cluster using a bench +12V supply, had to swap a few around to get the polarity right for all to work correctly BUT...

Strange thing, some time days later, my headlights wouldn't come on.  Hi beams worked, but would "latch on" until I removed power by shutting off lights.  Behaved just as a diode on a relay coil can be used to make a "latch on"  circuit.  I started swapping in normal bulbs for the LEDs on the cluster.  I thought I had narrowed it down to the blinker bulb; headlights worked again.  A few days later, the same thing.  Ultimately I swapped back all normal incandescent bulbs and problem went away!

 

Note: I found that Philips bulbs are considerably brighter than OSRAM bulbs of the same rating.

Edited by Swiss 2002Tii
additional info

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(edited)

Update:

As per AustrianVespaGuy's suggestion, I took the cluster out to work on it. I hooked up a 9V battery per his suggestion and diagram, and nothing.

 

Frustrated, I thought I must have hooked up something wrong and fried everything (wouldn't be the first time). So, I took one of the LED's and connected it directly to the 9V. It lit up beautifully. So pointing more towards the board is fried. Something got me looking though at the LED base more closely, and I noticed that unlike the incandescent bulbs, there are two wire contacts on both sides of the bulb (as opposed to one on each side). Sorry in advance for the crappy cell pics.

 

Side one: Notice how at the base there are wires on both sides

IMG_8963.thumb.jpg.147228676af99d27fb0703c725aacfd9.jpg

 

 

Side two: Same thing

IMG_8964.thumb.jpg.e337f248c122f652e1c00febb99cd9cc.jpg

 

So, I bend the wire and fold it over meaning there is only one wire per side, just like the incandescent bulbs

IMG_8965.thumb.jpg.299dc09867a8269291b2b91febd4f3c6.jpg

 

Putting the LED's back into their holders I test again with the 9V, and magically they light up! I test rotate the negative/positive to verify the bulbs do not care about the polarity.

IMG_8967.thumb.jpg.69f74056a21c2d57a8914c870a307336.jpg

 

Voila! Bulbs dim and light up as expected! Now the only issue is the turn signal indicator stays lit all the time and blinks extra bright when signals are active. I have seen several articles about this being an issue with the LED conversion and will find the appropriate article to fix that before fully reinstalling the cluster.

 

IMG_8969.thumb.jpg.19b1ff034c569fc00ce0fa570c15f096.jpg

 

These bulbs are SO much brighter than the originals. I'm very happy with the result. I may actually have to turn them down from my default high power for normal driving. Now on to upgrading the rest of the bulbs in the car as well.

 

Thanks again to everyone who chimed in!

 

-Nick

 

 

Edited by photocrasher
Duplicate photo by accident
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You'll love doing the ones on the outside, headlights are so much brighter with less energy consumption.  You'll need the electronic flasher relay.

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This just made me wonder why you want the instrument cluster to shine on your face? I think it will be rather uncomfortable in dark unless turned down.

I have never used the full power of the original bulbs. Probably some of them are actually original and definitely not at their brightest anymore.

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Well done @photocrasher! I suppose the little leads just didn't stick out quite far enough to touch the bulb holder contacts until you re-bent them, but glad it all works now! FYI, to @Tommy's point and despite the truth that it shouldn't work very well, I've actually been lucky that I can dim my backlight LED bulbs somewhat with the stock rheostat.  Nothing like incandescents of course, but they sorta go from SUPER bright to normal bright to off.  Also, I found the LED bulb in the turn signal indicator to be much too bright, especially at night, and switched that one back to the dimmer incandescent.

 

@irdave I fully agree that upgraded LED bulbs for the tail, turn, reverse, and stop lights are awesome, I actually do NOT recommend them for the headlights.  They will seem brighter because the LEDs do put out more light, and you notice that a lot on the ground or your garage door right in front of you, but unless optics are changed to properly channel the light from the LEDs you actually don't get as much throw down the road and there's a lot more light scattered to places you don't want, like at oncoming drivers.  More light yes, but not more light were you really want it, so I advise a higher amount of research and caution before going with LED headlights. But definitely go ahead with all of the corner lights!

 

@Swiss 2002Tii What year is your headlight wiring stock?  I'm about 95% certain that what's happening is that your LED lights are in series with the high beam relay and indeed do keep the relay coil energized.  We can certainly fix this, but I'll need a bit more info on your particular wiring to help diagnose it.

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Thanks AVG, my Tii is a May 1972, baccording to Mike that would make the harness the same as from a ‘73. The instrument cluster is from June(?) ‘72; I bought it to replace the original that was removed at time of purchase.

 I’m happy with the brightness of the Philips bulbs, and I ‘ve learned that Switzerland MFK does not allow mods, not even LEDs, so I’m good.

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Ok,well I guess I won't worry about it too much then.  Glancing at the '73 diagram it seems that should NOT have a relay for the high beams, so maybe our original theory is dead anyway.  Schade that you can't have fun modifying things, but hey, if you're happy, I'm happy! Prost!

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I had a problem with the Superbright LED's on my 75.  I had to cut the contacts so the wire just went down one side.  If it wraps up on the other side, the panel will short out and blow a fuse. 

 

I think that this is your problem.

 

Let me know

 

 

 

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