Scully Posted May 1, 2014 Share Posted May 1, 2014 (edited) I'm working my way through the conversion and its all going well completed the window switches, cup holders and the climate gages. start on the centre triple gauge and hit a road block the original LED's have 4 contacts 1 pos and 3 neg, the guide says that just the top pair of contacts should be used (because the new LED's have 2 contacts). I know I'm getting the polarity correct but they are just not lighting up. when I put the original LED's back in they work again. Tried a few LED's now just in case one was dead but still no luck... should I try and soulder all the negative contacts on the board to make one big negative? i havent tried that yet as im not sure how the current passes through the original contacts, whether all negs are equal or not Edited May 1, 2014 by Scully Quote Link to comment Share on other sites More sharing options...
Husky Posted May 1, 2014 Share Posted May 1, 2014 Hmm, it's been a few too many years for me to remember exactly which pads do what. But you need to look at the orientation of them before they come off, you can use a multimeter set to continuity to test the LED polarity. The multimeter sends out a very low current that will very dimly light up the LED if the correct polarity is found. So, check the polarity of the LED (and which pads to use) before you take it off of the board by touching combinations of pins with the multimeter, once it lights you know you found the right ones, mark them up with a pen. Then check the polarity of your new LED's, once you find the right way round, pop them on. What I would say, is that it is very easy to overheat them, best to get some proper flux, dip the LED in it then touch it onto the tinned iron. it'll wick up the solder nicely, make sure the board pads are nice and clean and put the two together. Quote Link to comment Share on other sites More sharing options...
Scully Posted May 1, 2014 Author Share Posted May 1, 2014 Hmm, it's been a few too many years for me to remember exactly which pads do what. But you need to look at the orientation of them before they come off, you can use a multimeter set to continuity to test the LED polarity. The multimeter sends out a very low current that will very dimly light up the LED if the correct polarity is found. So, check the polarity of the LED (and which pads to use) before you take it off of the board by touching combinations of pins with the multimeter, once it lights you know you found the right ones, mark them up with a pen. Then check the polarity of your new LED's, once you find the right way round, pop them on. What I would say, is that it is very easy to overheat them, best to get some proper flux, dip the LED in it then touch it onto the tinned iron. it'll wick up the solder nicely, make sure the board pads are nice and clean and put the two together. checks for the quick reply, going to pop to maplins to get a new multi meter would you suggest testing whilst the board is connected to the car? some of the LED's work in pairs in series as well which i can image meaning probing over the both of them Quote Link to comment Share on other sites More sharing options...
Husky Posted May 1, 2014 Share Posted May 1, 2014 (edited) The way I ended up doing it was more time consuming in the short term but much faster long term. I checked the polarity of an LED marked it down including pads to use tested my new LED was a working one, the polarity, and was of the correct colour de-soldered the old LED soldered on the new LED took it to the car, verified it worked, was at the correct brightness and with no damage Obviously after doing a few cars worth I did them in batches of three LED's or so at a time, but it's a quick job to push the connector half home and turn the ignition round. Breaking the task down to batches of LED's meant that I could fault find as I went along, just in case one LED not working caused others to not work. EDIT: rereading what you asked... You shouldn't need to test on the car I don't think, with the low current provided from the multimeter you get to probe about and figure out what's what. Obviously a lot of the earths will be common, so you'll find you can keep on one earth and probe for continuity on other LED's pads to find their earths, the pad that's left with no continuity buzz will be your feed. Edited May 1, 2014 by Husky Quote Link to comment Share on other sites More sharing options...
Scully Posted May 1, 2014 Author Share Posted May 1, 2014 got the new meter, really helping... always meant to get one. its allowed me to bin half a dozen LED's, but my polarities were all good so I'm going to put it down to being to heavy handed with heat like you said. ill let you know how i get on 1 Quote Link to comment Share on other sites More sharing options...
flyboy Posted May 1, 2014 Share Posted May 1, 2014 What soldering iron are you using. I got a digital temperature controlled solder station for mine which was about £50 but ensured i diddnt burn out the leds. When you move onto the leds near to the tacho and speedo you must make sure you have a very short heat cycle next to the shafts as you can damage them easily. If you want some clear needles to play about wiith to change the needle colours then PM me I bought extra from the ststes when I did mine. 1 Quote Link to comment Share on other sites More sharing options...
Husky Posted May 1, 2014 Share Posted May 1, 2014 got the new meter, really helping... always meant to get one. its allowed me to bin half a dozen LED's, but my polarities were all good so I'm going to put it down to being to heavy handed with heat like you said. ill let you know how i get on Great news Have fun! Quote Link to comment Share on other sites More sharing options...
Scully Posted May 1, 2014 Author Share Posted May 1, 2014 success! and before anyone says I know the red LED on the left is smaller, its because I melted the original. The intensity looks the same though so I'll see if its noticeable through the needles when back together - the different angles on that LED shouldn't have much effect when just lighting up the needle. cheers for your input guys What soldering iron are you using. I got a digital temperature controlled solder station for mine which was about £50 but ensured i diddnt burn out the leds. When you move onto the leds near to the tacho and speedo you must make sure you have a very short heat cycle next to the shafts as you can damage them easily. If you want some clear needles to play about wiith to change the needle colours then PM me I bought extra from the ststes when I did mine. its only a cheap maplins one like the ones back in school. it turns on, gets hot, and melts stuff! I've adjusted my technique accordingly though. 1 Quote Link to comment Share on other sites More sharing options...
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