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Optimal Electrical Performance: System Cleaning & Maintenance

September 23, 2010 | Troubleshooting & Repair


By: Tom Farnam

A recent conversation about converting a 356 from a 6 volt to 12 volt electrical system led to me sending a friend a lengthy email about how to keep that 6 volt system performing properly. Recent posts on the 356 Talk List make it reasonably clear many think of the "conversion" of their systems as the only way to deal with dim lights, starter problems and similar issues. I think that you will be amazed at just how well a 6 volt system can work if properly cleaned and maintained.

First and foremost, if you have that car in "project" status, go through and CLEAN EVERY electrical connection on the car. The biggest single issue is corrosion, either in the form of copper oxide or iron oxide. So our objective is to get the metal clean (as if a Concours judge were going to be taking these connections apart) and then apply a light coating to reduce the air/water contact in the future. Not in "project" status? All of this can be done on a fully operative car, just be sure to disconnect the battery. It's a great winter task, which can easily be done in stages as time allows. (Or as crises happen - thought my ignition switch had "shot craps" recently, it turned out to be nothing more than some dirty contacts on the fuse block, so these words are coming from a cleaning believer ) We'll go "front to back" with some specific suggestions, but first gather your tools and equipment.



  • Brushes, including:
    • battery terminal brush from your FLAPS (friendly local auto parts store) steel wire hand brushes in various sizes and shapes (most should be fine wires, not coarse painter's wire brushes) brass wire hand brush if you can find one (try shoe repair shop for a suede brush)
    • old toothbrushes
    "Scotch-brite" pads from 3M, which are a synthetic steel wool, in various grades Baking soda Plastic or glass dishes in various sizes Spray container of "contact cleaner" from electronics store like Radio Shack
  • Silicon or similar dielectric material (I'll call it Si after this to save space). You do NOT want silicone adhesive, you do want a spray can of Si and a tube of Si lubricant (my tube of Dow Corning Compound 4 came from an aircraft supply store in the early 70's, still has not been used up, as it's like Brylcreem, "a little dab 'll do ya". It serves to exclude air and water from the surfaces after you clean them. It should be applied to connections after assembly.

Optional but helpful in speeding the process:

  • Bench grinder with fine wire wheel - you are only trying to remove oxidation, not basic metal Dremel tool with several sizes and shapes of wire wheels Electric drill or air-powered die grinder with various size/shape wire wheels Typewriter eraser (the pencil-shaped one), which has just enough abrasive to clean the contacts in the bottom of bulb sockets A VOM can be handy to check voltage drops and resistance, you can get a decent digital readout VOM for under $20 from Radio Shack Joe Leoni's (356 Electrics) book for your car, or at the very least the wiring chart for the car - a color chart makes it easier, but if you learn to read it the original factory chart it gives all the details. This is your big chance to correct any previous errors in replacing wiring. Switch Saving Relay from
  • Head Light Relay from

CLEANING Now, let's start cleaning, more or less front to back on the car. Remember, the metal surfaces are copper, brass, and some steel, but none of them need harsh treatment, just enough to remove the oxide coating. If they are visibly shiny, you are done. And the wire ends should all be cleaned by a dip in baking soda solution, until they stop fizzing. That helps clean under the insulation as well. Be sure they are DRY before you reassemble them, and a small hair dryer (low heat) or air blower might be useful to speed that process.



  • Battery Cables

    Disconnect both cables, always remove the negative first and replace it last.

    • Negative Cable

      Completely remove the negative cable from the car. If you have the flat braided copper cable, it can be soaked in a baking soda solution. If not, the "tinned" wires (the soldered bunch) can and should be soaked in the baking soda to remove any corrosion between the copper fibers. In any case, use a steel wire brush to clean both ends, after you have removed the clamp from the battery terminal end. Disassemble the clamp, clean all the parts and reassemble. Also clean the bolt and washer from the other end. When you are finished you can put a VERY light coat of Si on the connections, it will help reduce future corrosion by excluding the air and water.

    • Positive Cable

      You can't take the positive cables out of the car (well, you can, but...), but you should remove the clamp entirely from the cable end, soak the tinned end in baking soda solution until it quits fizzing. The clamp should be completely disassembled and cleaned with wire brushes. After assembly, a light coat of Si will help slow future corrosion.


    Battery Terminals

    Put the battery on a workbench and clean the posts with the concave part of your battery terminal brush. (A useful tool under the battery for this task and several other things like sorting nuts, bolts, washers from the "spares can" is an old plastic cafeteria tray.)


    Battery Case

    This is a great time to clean the case with your baking soda solution.


    Battery Box Floor
    While you have the battery out it's a good time to clean it with your baking soda. Be sure you have the wooden tray or hard plastic sheet that is supposed to be under your battery, depending on the model.


    Fuel Sender

    Clean contacts and wires.


  • Fuse Block

    A WIRING CHART is essential to work on the fuse block. (Yes, this is under the dash on earlier cars.) You need to disconnect and label each wire, then take the fuse block out of the car. Also remove all the fuses, and the relays. Label everything as you go! Now, clean all those wire ends so they are shiny. The ends in the fuse block should be "tinned" (soldered to make a solid bundle rather than loose wires). Again, soaking them in baking soda solution will help clean under the insulation on the ends. Clean and check all the connecting blocks and "jumper bars" on the fuse block. Here's where the VOM is almost essential, to be sure everything is without resistance.

    AFTER you have finished the fuse block and are ready to reinstall and reconnect, install the Head Light Relay from 356 Electrics while you are in there. It's not difficult, and you and your 356 friends will be amazed at how well the headlights work.


  • Headlights, Parking Lights & Turn Signals

    ALL lamps, including head lamps, turn signals, marker lights - clean ALL connections. If your headlamp connectors can be taken apart, do it. Be sure to carefully remove the bullet connectors from the lamp sockets, and clean the inside of those holes, and also gently wire brush the inside of all bulb sockets and outside of the bulbs. Try using that "stick" typewriter eraser on the center contacts of the sockets. When all is clean, apply light coat of Si to the inside of the socket barrel - not the contacts. Ground connections are as important as the power leads, be sure they are clean!



    Remove them from the car. Clean all wire connections and Si after reassembly.


  • Brake Light Switch (on master cylinder)

    Clean contacts and wires. Unless you are rebuilding the brake MC, you are better off not to remove the switch from the MC.


  • Instruments

    There a lots of wires and all of the connections need to be cleaned. Save yourself time and mark the wires as they are removed. Unless you really like lying on your back working upside down, it's a lot easier to remove the instruments for cleaning. Here is where you will really want to use the "contact cleaner", as the baking soda solution might be hard to remove. You will want to remove each bulb, and clean the sockets, bulbs and connecting wires while you are there. Want brighter instrument lighting? Replace the .6 watt bulbs with the Osram #3799 at 1.2 watts.

    Remember, the instruments are grounded through the "bale" which holds them in place, so clean the contact surfaces for those on the instrument cases while you are in there. And when you reinstall the instruments, be sure the points on the bale actually make good firm contact with a metal surface.


    Switches for ignition, lights, wipers, etc.

    Again, mark the wires before you disconnect them, then remove the switch from the dash to clean it. If you have a non-working clock or problems with any of your instruments, now is the time to have them repaired. You can have this done via the usual suspects (NLA, Stoddard, Zim's) or North Hollywood Speedometer and Palo Alto Speedometer.


  • Interior Lights

    Clean the switches in the door posts, then also remove and clean the lights and all the connections to them.



  Clean all contacts and wires. Don't forget to dip these wires in your baking soda solution, that big fat one carries full voltage and is in a more hostile environment (under the car with all that water we drive in) than the battery cables. Apply a bit of Si after you clean and reassemble. Install Joe Leoni's "Switch Saving Relay" - reduces the current load on your starter switch and helps the engine start better. If you have the engine out, this is a great opportunity to remove the starter and replace the starter bushing (see Tech articles on Registry site for details); the bushing can be replaced with engine in place, but it's much easier when engine is out. Clean the starter, check the solenoid, clean all the surfaces. Check and clean the ground strap from the transmission to the car body. This is generally a braided strap, and should be treated like the battery ground cable. Disconnect both ends, clean, reinstall.



  • Voltage Regulator

    The voltage regulator should be disconnected (mark the wires first), removed and all contacts cleaned. Clean all the wires and connections, both from battery and generator.


    Boots on Generator and other Contacts

    New boots are easy to do now, and will add protection. A bit of Si on the inside will help.


  • Connections to oil temperature, oil pressure, tachometer (if electric)

    All connections should be cleaned and restored with new boots.



  • Tail Lights

    You will need to remove the tail light housings from the body to get them really clean.

    NOTE - the teardrop housings are grounded by means of a sheet metal strap, and if that's not present it should be replaced with a short length of wire. Just bolting them into the openings does not provide complete ground. BE CAREFUL REMOVING THE HOUSINGS, YOU MAY NEED TO CLEAN OFF UNDERCOATING AND "JUNK" TO GET THE BOLTS LOOSE. Check the sockets, they should be tight in the housings. (The author just had the solder joint break in one.) This is your chance to clean and paint any corroded housings. There have been good reports on 356 Talk of improved light reflection when rusty units are painted with gloss white rust resistant paint. Don't forget to remove and clean all bullet connections, coat with a little Si after reassembling. Use new boots when you reassemble.


  • License Plate & Back-Up Lamps

    Clean and repair as needed, install with new gaskets and boots.


Again, I think that you and those around you will be amazed at just how well a 6 volt system can work when properly cleaned and maintained.