Hi there my fellow Pelicans. I have over the last couple of weeks been trying to find a solution to the common problems you get when fitting LED bulbs to the indicators on our cars without having to fit the nasty resistors (which puts back some of the problems I was trying to solve - reduced current on the circuit and wires!!). Now that I have completed the project and tested it, I would like to share this simple upgrade with you all, should you wish to do the same
I should point out that this was done on my 78SC, which has the 4 pin relay (Pelican P/N: 914-618-303-11-M44 "Hazard Flasher/Blinker Relay, 911 (1974-84)) and not the 3 pin version as found in the 1985-89. I would have to see the circuit diagram and more info on these to know if this upgrade would work.
Parts List:
.- Replacement LED indicator bulbs. NOTE: You must replace all bulbs or you will burn out the new relay!!!
.- 1x BMW LED Flasher relay (this is the one I got:
http://www.ultraleds.co.uk/product_info.php?cPath=44_64&products_id=978&osCsid=8a3d27c6ff8ba53dabbf9d69bedc8125)
.- 2x female spade terminals (
http://www.cybermarket.co.uk/ishop/923/shopscr2376.html)
.- 1x female spade piggy back terminal (
http://www.cybermarket.co.uk/ishop/923/shopscr2388.html)
.- Some brown wire.
Project:
1) Remove and replace all the indicator bulbs with the new LED ones. I would do this first!! If you should do the relay first and decide to run a test with the existing bulbs still connected, the current will burn out the new relay
2) Pull out the two left most gages in the car (fuel level and oil pressure).
3) Locate the correct relay and pull it out. A quick way to do this is to turn on the hazard lights and touch the relays - the one that is clicking is the one you will be replacing.
4) Put the new BMW relay in the socket - make sure you do not bend any of the pins. There is not a lot of space in there!!
5) Test your indicators - The hazards and the indicators should now work as expected. The only problem left is that the left and right indicators in the rev-counter will not light up. This is because you have removed that part of the circuit (the 4th pin on the relay!). Not to worry, that is what the additional component are there to fix
6) If you look at the back of the sockets for the left and right indicator bulbs in the rev-counter, you will se that they both have two wires attached to them via spade terminals. Using the new terminals and extra wire that you have, you are going to replace the part of the circuit that feeds the signal back to the missing relay pin so that it goes to earth (negative terminal on the battery!!). Good news is that you can do it all on the back of the rev-counter
7) Disconnect the blue/white wire from both the bulbs, and tape up the ends. I opted not to cut the wire so that I had the ability to revert back to a factory relay if I ever want to in the future.
8) Make up a new cable containing three spade terminals in the following way: [female spade terminal]--------------------[female spade terminal]-----------------[female spade piggy back terminal].
9) connect the first spade terminal to one of the bulbs (the terminal you removed the blue/white connector from), the second spade terminal to the second bulb (again the terminal you removed the wire from). Then remove any of the connectors at the bottom of the rev-counter with a brown wire going to it. Put the last female spade piggy back terminal in its place, and reconnect the brown cable to the piggy back pin on the new terminal.
Job done - your new LED indicators will work, and the bulbs in the rev-counter will also work as expected.