Cluster LEDs - how did you determine polarity?
 

While I had the cluster out of my car I was planning to swap all the lights out with LEDs. I did this in my 86 hardbody and it made a huge difference in visibility and they'll of course last much longer. Anyway, in my truck I just put them in, if the light didn't work, I yanked the cluster and reversed it. Is that the best way to do it in these cars as well, or does someone have a pinout/diagram of the cluster that shows the polarity of the contacts around the lights?

With a DMM (Digital Multi Meter)
 

1.You CAN easily figure out polarity (I.C. (Instrument Cluster) plugged in Of Course!

2. Wiring Diagram pertinent to your chassis will show + or - .

Look around Rev190 W201

Reversing polarity will not damage LEDs, so yes, that is the way to do it. When it lights up, polarity is correct.

Alrighty, I'll stick to that method then.

Just FYI, I converted to LED's and had continual lighting issues on the cluster. Finally just pulled them all out and went back to incandescents. Became an expert at pulling that cluster. Thirty one times best I recall. Always pulled the steering wheel off and worked through the left vent. Pretty easy after you've done it a few. LED's in most other places on the car work fine but that cluster was hell!

Oh? Would you mind sharing the nature of the problems?

It cannot be inherent issue with LED's, must be a contact issue between LED and the socket or the socket to the cluster. Try cleaning the socket contacts with 600 grit wet dry paper and the pcb traces with an eraser.

Can't truly remember so I can't help. It may have all been 'operator error'. There was a guy over at one of the 201 boards that had done it with no problems, and that's what enthused me, so I went ahead. Happened about 8 years ago so details are murky.

I put LED's in my 84 & 85 300D. I used cheap Chinese ones from ebay. A few failed, but most are still working after ~3 yrs. A couple things of notes:

Some LED's have contacts which will short out the M-B bulb holder. That will smoke a trace on the cluster's circuit board. Look close and test w/ an ohmmeter to avoid.

Some LED's will not fit, even though sold as the correct bulb#. I recall this was true of some small ones for the push-button switch. They have a square board which doesn't quite fit in the round hole.

For the light tunnels in a W123, use LED's w/ forward shining diodes. Those light the speedometer much better than incandescent bulbs did.

The current draw of the "BATT warning" bulb is used to boot-up the alternator, along w/ 2 other dash bulbs. My LED's don't draw quite enough for that, but once I rev the engine >1200 rpm, the alternator boots-up and the bulbs go out. That is probably due to residual magnetism in the armature. If that bothers you, use an incandescent bulb there.

too much work in this procedure :)

just unscrew left (driver) side speaker and push cluster out by hand. POC :D


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Thanks for the info Bill. I think I'll just replace the "heavy use" items with LEDs and leave the rest of them.

Can you see, and find, all the connections? Some of those don't reach after you can get your hands into the cluster opening.:confused:

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yes easy..when pushed out just access from clusters right bottom side and disconnect...


note: my hands are "highlander" type so I guess anyone can do it :)

cheers

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