By Mike Robbins
One of the weak links on 356s is that of inadequate illumination of the instruments. Many owners have replaced the original 0.6 watt bulbs with 1.2 watt bulbs but they still leave something to be desired. One of our well known suppliers sold 6 volt LED units that fit the receptacles on the instruments but apparently sold out and discontinued them. I had purchased some of these and they really lit up the instruments. As evidence, at the Portland Porsche Parade in 2006, I returned to the parking lot one night with the top down and slowly passed a group of guys who were BSing. A couple of them saw my brightly lit instruments and called for me to wait. They were eager to know what I had.
Recently, in the course of making a change to other wiring to my instruments, I accidently grounded the power wire to the LEDs and blew all but one of them and also let all of the smoke out of the wires. After determining that the original source no longer offered them, I decided to build my own. The biggest problem was finding a shell to fit the receptacles. I got lucky and found what appears to be the same part used by the original supplier. So if you would like to follow my lead, here's the scoop.
- Purchase house brand 1/2" compression brass sleeve adapter no. 43057 at Ace Hardware. They come in packages of two. One used per finished assembly. Herein termed "housing".
- Purchase NTE brand LED no. 30059 or equal, at an electronics supply house. They are also two per pkg. One used per finished assembly.
- While at electronics supply, purchase 300 ohm x 1/4 watt resistor. NTE brand come four per pkg. One used per finished assembly.
- If not already on hand purchase a pack of uninsulated 1/4" male spade connector. If you have insulated ones, cut the insulation away. One used per assembly [See 10 below]
- If not already on hand, purchase a small can of paint-on insulation.
- If not already on hand, purchase a tube of silicone sealant [hardening] or 2-part paste epoxy.
- I paid about the same price for the materials to make eight lights as I paid for one of the vendor's units. How much is your time worth?
- If you don't already have one, those nifty little "octopus" tools with alligator clips to hold the parts together for soldering are a big help for this job.
- Note that the longer of two leads on the LED is positive. Cut this to 1/4" long. Solder the shortened lead to the spade connector so that the flat, lead end of the LED is flush with the straight end of the housing and the connector's transition is at the flared end of the housing. Paint the bare conductor, including the small end of the spade connector, with the insulating paint.
- Cut the other lead from the LED to 1/4". Cut one lead from the resistor to 1/4". Lay the shortened ends side by side and solder them together.
- Feed the soldered assembly into the housing from the straight end.
- Cut the resistor lead so it protrudes approx. 1/32" from the flared end of the housing. 5. Solder that lead to the flared end of the housing. After assuring that the soldered connection is solid, trim away excess solder and wire lead. Diagonal cutters work well for this.
- Check fit of the assembled unit in the receptacle on the back of the instrument. If loose, lay a bead of solder lengthwise on the outside of the housing and then trim [file] to fit snugly...but not too tight...a solid electrical connection but readily removable.
- Hold the base of the LED tightly against the flat end of the housing and wrap the interface tightly with masking tape, electrical tape or whatever. Those without three hands will be challenged by this. The idea is to have no gap between the base of the LED and the end of the housing.
- Test the unit by hooking jumper wires to the spade connector and fuse no. 2, 3 or 4 in the car. Connect the housing to a good ground. If it lights, you're ready to seal it up.
- Clamp the assembly, open end up, in a vise...but not too tightly. Fill the housing with the silicone or epoxy. Let it set over-night. When you come back the next day you may find that the sealant has run down into the housing and left a void. Fill the void so that sealant-filler is flush or beyond the flared end of the housing. You don't want the power lead [gray wire under the dash] or its terminal to contact the brass housing.
- If you have an early car with the screw connection type bulb holders, you can change to the blade type. [I have a good supply.] Alternatively, you can take the bulb holder apart and solder the brass bar with the screw hole instead of soldering the male blade terminal to the positive LED lead.
- The final test is to wait for solid night, grab a beer and your latest issue of the 356 Registry, get in the car, turn on the instrument lights and read the new magazine. Gut Lesen!
One owner '58 Speedster 84617